dr.ir. M.A.P. Pertijs

Projects history

1. An Ultrasound Matrix Transducer for High-Frame-Rate 3-D Intra-cardiac Echocardiography
   dos Santos, Djalma Simões; Ossenkoppele, Boudewine; Hopf, Yannick M.; Soozande, Mehdi; Noothout, Emile; Vos, Hendrik J.; Bosch, Johan G.; Pertijs, Michiel A.P.; Verweij, Martin D.; de Jong, Nico;
   Ultrasound in Medicine \& Biology,
   Volume 50, Issue 2, pp. 285--294, February 2024. DOI: 10.1016/j.ultrasmedbio.2023.11.001

2. A 125μm-Pitch-Matched Transceiver ASIC with Micro-Beamforming ADC and Multi-Level Signaling for 3-D Transfontanelle Ultrasonography
   Peng Guo; Fabian Fool; Zu-Yao Chang; Emile Noothout; Hendrik J. Vos; Johan G. Bosch; Nico de Jong; Martin D. Verweij; Michiel A. P. Pertijs;
   IEEE Journal of Solid-State Circuits,
   pp. 1--14, 2024. early access. DOI: 10.1109/JSSC.2024.3355854

3. A 2000-Volumes/s 3D Ultrasound Imaging Chip with Monolithically-Integrated 11.7x23.4mm2 2048-Element CMUT Array and Arbitrary-Wave TX Beamformer
   Nuriel N.M. Rozsa; Zhao Chen; Taehoon Kim; Peng Guo; Yannick Hopf; Jason Voorneveld; Djalma Simoes dos Santos; Emile Noothout; Zu-Yao Chang; Chao Chen; Vincent A. Henneken; Nico de Jong; Hendrik J. Vos; Johan G. Bosch; Martin D. Verweij; Michiel A. P. Pertijs;
   In Dig. Techn. Paper IEEE Symposium on VLSI Circuits (VLSI),
   2024. Accepted.

4. A Pitch-matched Low-noise Analog Front-end with Accurate Continuous Time-gain Compensation for High-density Ultrasound Transducer Arrays
   Peng Guo; Zu-Yao Chang; Emile Noothout; Hendrik J. Vos; Johan G. Bosch; Nico de Jong; Martin D. Verweij; Michiel A. P. Pertijs;
   IEEE Journal of Solid-State Circuits,
   Volume 58, Issue 6, pp. 1693--1705, June 2023. DOI: 10.1109/jssc.2022.3200160

5. A 1.2 mW/Channel Pitch-Matched Transceiver ASIC Employing a Boxcar-Integration-Based RX Micro-Beamformer for High-Resolution 3-D Ultrasound Imaging
   Peng Guo; Fabian Fool; Zu-Yao Chang; Emile Noothout; Hendrik J. Vos; Johan G. Bosch; Nico de Jong; Martin D. Verweij; Michiel A. P. Pertijs;
   IEEE Journal of Solid-State Circuits,
   Volume 58, Issue 9, pp. 2607--2618, September 2023. DOI: 10.1109/jssc.2023.3271270

6. A Pitch-Matched High-Frame-Rate Ultrasound Imaging ASIC for Catheter-Based 3D Probes
   Yannick M. Hopf; Djalma Simoes dos Santos; Boudewine W. Ossenkoppele; Mehdi Soozande; Emile Noothout; Zu-Yao Chang; Chao Chen; Hendrik J. Vos; Johan G. Bosch; Martin D. Verweij; Nico de Jong; Michiel A. P. Pertijs;
   IEEE Journal of Solid-State Circuits,
   Volume 59, Issue 2, pp. 476--491, February 2023. DOI: 10.1109/JSSC.2023.3299749
   
   Abstract: ...

   This article presents an application-specific integrated circuit (ASIC) for catheter-based 3-D ultrasound imaging probes. The pitch-matched design implements a comprehensive architecture with high-voltage (HV) transmitters, analog front ends, hybrid beamforming analog-to-digital converters (ADCs), and data transmission to the imaging system. To reduce the number of cables in the catheter while maintaining a small footprint per element, transmission (TX) beamforming is realized on the chip with a combination of a shift register (SR) and a row/column (R/C) approach. To explore an additional cable-count reduction in the receiver part of the design, a channel with a combination of time-division multiplexing (TDM), subarray beamforming, and multi-level pulse amplitude modulation (PAM) data transmission is also included. This achieves an 18-fold cable-count reduction and minimizes the power consumption in the catheter by a load modulation (LM) cable driver. It is further explored how common-mode interference can limit beamforming gain and a strategy to reduce its impact with local regulators is discussed. The chip was fabricated in TSMC 0.18-μm HV BCD technology and a 2-D PZT transducer matrix of 16 × 18 elements with a pitch of 160 μm and a center frequency of 6 MHz was manufactured on the chip. The system can generate all required TX patterns at up to 30 V, provides quick settling after the TX phase, and has an reception (RX) power consumption of only 1.12 mW/element. The functionality and operation of up to 1000 volumes/s have been demonstrated in electrical and acoustic imaging experiments.

7. An ultrasound matrix transducer for high-frame-rate 3D intracardiac echocardiography
   Djalma Simoes dos Santos; Boudewine Ossenkoppele; Yannick M. Hopf; Mehdi Soozande; Emile Noothout; Hendrik J. Vos; Johan G. Bosch; Michiel A. P. Pertijs; Martin D. Verweij; Nico de Jong;
   Ultrasound in Medicine \& Biology,
   2023. accepted.
   
   Abstract: ...

   Objective: This paper presents the development of an ultrasound matrix transducer prototype for high frame rate three-dimensional (3D) intracardiac echocardiography (ICE). Methods: The matrix array consists of 16 ×18 lead zirconate titanate (PZT) elements with a pitch of 160 µm × 160 µm built on top of an application-specific integrated circuit (ASIC) that generates transmission signals and digitizes the received signals. To reduce the number of cables in the catheter to a feasible number, we implement subarray beamforming and digitization in receive and use a combination of time-division multiplexing and pulse amplitude modulation data transmission, achieving an 18-fold reduction. The proposed imaging scheme employs seven fan-shaped diverging transmit beams operating at a pulse repetition frequency of 7.7 kHz to obtain a high frame rate. The performance of the prototype is characterized and its functionality is fully verified. Results: The transducer exhibits a transmit efficiency of 28 Pa/V at 5 cm per element and a bandwidth of 60% in transmission. In receive, a dynamic range of 80 dB is measured with a minimum detectable pressure of 10 Pa per element. The element yield of the prototype is 98%, indicating the efficacy of the manufacturing process. The transducer is capable of imaging at a frame rate of up to 1000 volumes/s and is intended to cover a volume of 70° × 70° × 10 cm. Conclusion: These advanced imaging capabilities have the potential to support complex interventional procedures and enable full-volumetric flow, tissue, and electro-mechanical wave tracking in the heart.

8. A Pitch-Matched Transceiver ASIC for 3D Ultrasonography with Micro-Beamforming ADCs based on Passive Boxcar Integration and a Multi-Level Datalink
   Guo, P.; Chang, Z. Y.; Noothout, E.; Vos, H. J.; Bosch, J. G.; de Jong, N.; Verweij, M. D.; Pertijs, M. A. P.;
   In Dig. Techn. Paper IEEE Symposium on VLSI Circuits (VLSI),
   IEEE, pp. 1-2, 2023. accepted.

9. A prototype matrix transducer for high frame rate 3D intracardiac echography
   D. Santos; Y. Hopf; B. Ossenkoppele; J. Bosch; R. Vos; M. Pertijs; N. de Jong; M. Verweij;
   In Proc. IEEE International Ultrasonics Symposium (IUS),
   2023. abstract, accepted.

10. Effect of SAR-ADC Non-Idealities on Medical Ultrasound B-Mode Imaging
    N. Radeljic-Jakic; A. Flikweert; Y. Hopf; N. Rozsa; M. Pertijs;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    2023. abstract, accepted.

11. Pitch-Matched Integrated Circuits for Ultrasound Transducer Arrays
    Y. Hopf; P. Guo; M. Pertijs;
    In Proc. Workshop on Advances in Analog Circuit Design (AACD),
    April 2023. invited presentation.

12. Measurement of Pipe and Fluid Properties with a Matrix Array-based Ultrasonic Clamp-on Flow Meter
    J. Massaad; P. L. M. J. van Neer; D. M. van Willigen; A. Sabbadini; N. de Jong; M. A. P. Pertijs; M. D. Verweij;
    IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control,
    Volume 69, Issue 1, pp. 309--322, January 2022. DOI: 10.1109/TUFFC.2021.3111710

13. A Compact Integrated High-Voltage Pulser Insensitive to Supply Transients for 3D Miniature Ultrasound Probes
    Yannick M. Hopf; Boudewine Ossenkoppele; Mehdi Soozande; Emile Noothout; Zu-Yao Chang; Hendrik J. Vos; Johan G. Bosch; Martin D. Verweij; Nico de Jong; Michiel A. P. Pertijs;
    IEEE Solid-State Circuits Letters,
    Volume 5, pp. 166--169, 2022. DOI: 10.1109/lssc.2022.3180071
    
    Abstract: ...

    In this paper, a compact high-voltage (HV) transmit circuit for dense 2D transducer arrays used in 3D ultrasonic imaging systems is presented. Stringent area requirements are addressed by a unipolar pulser with embedded transmit/receive switch. Combined with a capacitive HV level shifter, it forms the ultrasonic HV transmit circuit with the lowest reported HV transistor count and area without any static power consumption. The balanced latched-based level shifter implementation makes the design insensitive to transients on the HV supply caused by pulsing, facilitating application in probes with limited local supply decoupling, such as imaging catheters. Favorable scaling through resource sharing benefits massively arrayed architectures while preserving full individual functionality. A prototype of 8 x 9 elements was fabricated in TSMC 0.18 μm HV BCD technology and a 160 μm x 160 μm PZT transducer matrix is manufactured on the chip. The system is designed to drive 65 V peak-to-peak pulses on 2 pF transducer capacitance and hardware sharing of 6 elements allows for an area of only 0.008 mm2 per element. Electrical characterization as well as acoustic results obtained with the 6 MHz central frequency transducer are demonstrated.

14. Imaging Scheme for 3-D High Frame Rate Intracardiac Echography: a Simulation Study
    M. Soozande; B. Ossenkoppele; Y. Hopf; M. Pertijs; M. Verweij; N. de Jong; H. Vos; J. Bosch;
    IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control,
    Volume 69, Issue 10, pp. 2862--2874, October 2022. DOI: 10.1109/TUFFC.2022.3186487
    
    Abstract: ...

    Atrial fibrillation is the most common cardiac arrhythmia, and normally treated by RF ablation. Intracardiac echography (ICE) is widely employed during RF ablation procedures to guide the electrophysiologist in navigating the ablation catheter, although only 2-D probes are currently clinically used. A 3-D ICE catheter would not only improve visualization of the atrium and ablation catheter, it might also provide 3-D mapping of the electromechanical wave propagation pattern, which represents the mechanical response of cardiac tissue to electrical activity. The detection of this electromechanical wave needs 3-D high frame rate imaging, which is generally only realizable in trade-off with channel count and image quality. In this simulation-based study, we propose a high volume rate imaging scheme for a 3-D ICE probe design that employs 1-D micro-beamforming in elevation direction. Such probe can achieve a high frame rate while reducing the channel count sufficiently for realization in a 10-Fr catheter. To suppress the grating-lobe artifacts associated with micro-beamforming in elevation direction, a limited number of fan-shaped beams with a wide azimuthal and narrow elevational opening angle are sequentially steered to insonify slices of the region of interest. An angular weighted averaging of reconstructed sub-volumes further reduces the grating lobe artifacts. We optimize the transmit beam divergence and central frequency based on the required image quality for electromechanical wave imaging (EWI). Numerical simulation results show that a set of 7 fan-shaped transmission beams can provide a frame rate of 1000 Hz and a sufficient spatial resolution to visualize the electromechanical wave propagation on a large 3-D surface.

15. Design and Proof-of-Concept of a Matrix Transducer Array for Clamp-on Ultrasonic Flow Measurements
    J. Massaad; P. L. M. J. van Neer; D. M. van Willigen; E. C. Noothout; N. de Jong; M. A. P. Pertijs; M. D. Verweij;
    IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control,
    Volume 69, Issue 8, pp. 2555--2568, August 2022. DOI: 10.1109/tuffc.2022.3186170
    
    Abstract: ...

    Common clamp-on ultrasonic flow meters consist of two single-element transducers placed on the pipe wall. Flow speed is measured non-invasively, i.e. without interrupting the flow and without perforating the pipe wall, which also minimizes safety risks and avoids pressure drops inside the pipe. However, before metering, the transducers have to be carefully positioned along the pipe axis to correctly align the acoustic beams and obtain a well-calibrated flow meter. This process is done manually, is dependent on the properties of the pipe and the liquid, does not account for pipe imperfections, and becomes troublesome on pipelines with an intricate shape. Matrix transducer arrays are suitable to dynamically steer acoustic beams and realize self-alignment upon reception, without user input. In this work, the design of a broadband 37x17 matrix array (center frequency of 1 MHz) to perform clamp-on ultrasonic flow measurements over a wide range of liquids (c = 1000 - 2000m/s, α≤1 dB/MHz.cm) and pipe sizes is presented. Three critical aspects were assessed: efficiency, electronic beam steering, and wave mode conversion in the pipe wall. A prototype of a proof-of-concept flow meter consisting of two 36-element linear arrays (center frequency of 1.1 MHz) was fabricated and placed on a 1 mm-thick, 40 mm-inner diameter stainless steel pipe in a custom-made flow loop filled with water. At resonance, simulated and measured efficiencies in water of the linear arrays compared well: 0.88 kPa/V and 0.81 kPa/V, respectively. Mean flow measurements were achieved by electronic beam steering of the acoustic beams and using both compressional and shear waves generated in the pipe wall. Correlation coefficients of R2 > 0.99 between measured and reference flow speeds were obtained, thus showing the operational concept of an array-based clamp-on ultrasonic flow meter.

16. A Pitch-Matched Transceiver ASIC with Shared Hybrid Beamforming ADC for High-Frame-Rate 3D Intracardiac Echocardiography
    Yannick M. Hopf; Boudewine W. Ossenkoppele; Mehdi Soozande; Emile Noothout; Zu-Yao Chang; Chao Chen; Hendrik J. Vos; Johan G. Bosch; Martin D. Verweij; Nico de Jong; Michiel A. P. Pertijs;
    IEEE Journal of Solid-State Circuits,
    Volume 57, Issue 11, pp. 3228--3242, November 2022. DOI: 10.1109/jssc.2022.3201758
    
    Abstract: ...

    In this article, an application-specific integrated circuit (ASIC) for 3-D, high-frame-rate ultrasound imaging probes is presented. The design is the first to combine element-level, high-voltage (HV) transmitters and analog front-ends, subarray beamforming, and in-probe digitization in a scalable fashion for catheter-based probes. The integration challenge is met by a hybrid analog-to-digital converter (ADC), combining an efficient charge-sharing successive approximation register (SAR) first stage and a compact single-slope (SS) second stage. Application in large ultrasound imaging arrays is facilitated by directly interfacing the ADC with a charge-domain subarray beamformer, locally calibrating interstage gain errors and generating the SAR reference using a power-efficient local reference generator. Additional hardware-sharing between neighboring channels ultimately leads to the lowest reported area and power consumption across miniature ultrasound probe ADCs. A pitch-matched design is further enabled by an efficient split between the core circuitry and a periphery block, the latter including a datalink performing clock data recovery (CDR) and time-division multiplexing (TDM), which leads to a 12-fold total channel count reduction. A prototype of 8×9 elements was fabricated in a TSMC 0.18- μm HV BCD technology and a 2-D PZT transducer matrix with a pitch of 160μm , and a center frequency of 6 MHz was manufactured on the chip. The imaging device operates at up to 1000 volumes/s, generates 65-V transmit pulses, and has a receive power consumption of only 1.23 mW/element. The functionality has been demonstrated electrically as well as in acoustic and imaging experiments.

17. Algorithm to Correct Measurement Offsets Introduced by Inactive Elements of Transducer Arrays in Ultrasonic Flow Metering
    Jack Massaad; Paul L. M. J. van Neer; Douwe M. van Willigen; Michiel A. P. Pertijs; Nicolaas de Jong; Martin D. Verweij;
    Sensors,
    Volume 22, Issue 23, pp. 2--14, November 2022. DOI: 10.3390/s22239317
    
    Abstract: ...

    Ultrasonic flow meters (UFMs) based on transducer arrays offer several advantages. With electronic beam steering, it is possible to tune the steering angle of the beam for optimal signal-tonoise ratio (SNR) upon reception. Moreover, multiple beams can be generated to propagate through different travel paths, covering a wider section of the flow profile. Furthermore, in a clamp-on configuration, UFMs based on transducer arrays can perform self-calibration. In this manner, userinput is minimized and measurement repeatability is increased. In practice, transducer array elements may break down. This could happen due to aging, exposure to rough environments, and/or rough mechanical contact. As a consequence of inactive array elements, the measured transit time difference contains two offsets. One offset originates from non-uniform spatial sampling of the generated wavefield. Another offset originates from the ill-defined beam propagating through a travel path different from the intended one. In this paper, an algorithm is proposed that corrects for both of these offsets. The algorithm also performs a filtering operation in the frequency-wavenumber domain of all spurious (i.e., flow-insensitive) wave modes. The advantage of implementing the proposed algorithm is demonstrated on simulations and measurements, showing improved accuracy and precision of the transit time differences compared to the values obtained when the algorithm is not applied. The proposed algorithm can be implemented in both in-line and clamp-on configuration of UFMs based on transducer arrays.
    
    document

18. A Tiled Ultrasound Matrix Transducer for Volumetric Imaging of the Carotid Artery
    dos Santos, Djalma Simões; Fool, Fabian; Mozaffarzadeh, Moein; Shabanimotlagh, Maysam; Noothout, Emile; Kim, Taehoon; Rozsa, Nuriel; Vos, Hendrik J.; Bosch, Johan G.; Pertijs, Michiel A. P.; Verweij, Martin D.; de Jong, Nico;
    Sensors,
    Volume 22, Issue 24, pp. 1--23, 2022. DOI: 10.3390/s22249799
    
    Abstract: ...

    High frame rate three-dimensional (3D) ultrasound imaging would offer excellent possibilities for the accurate assessment of carotid artery diseases. This calls for a matrix transducer with a large aperture and a vast number of elements. Such a matrix transducer should be interfaced with an application-specific integrated circuit (ASIC) for channel reduction. However, the fabrication of such a transducer integrated with one very large ASIC is very challenging and expensive. In this study, we develop a prototype matrix transducer mounted on top of multiple identical ASICs in a tiled configuration. The matrix was designed to have 7680 piezoelectric elements with a pitch of 300 μm × 150 μm integrated with an array of 8 × 1 tiled ASICs. The performance of the prototype is characterized by a series of measurements. The transducer exhibits a uniform behavior with the majority of the elements working within the −6 dB sensitivity range. In transmit, the individual elements show a center frequency of 7.5 MHz, a −6 dB bandwidth of 45%, and a transmit efficiency of 30 Pa/V at 200 mm. In receive, the dynamic range is 81 dB, and the minimum detectable pressure is 60 Pa per element. To demonstrate the imaging capabilities, we acquired 3D images using a commercial wire phantom.
    
    document

19. Measurement of pipe and liquid parameters using the beam steering capabilities of array-based clamp-on ultrasonic flow meters
    J. Massaad; P. L. M. J. van Neer; D. M. van Willigen; M. A. P. Pertijs; N. de Jong; M. D. Verweij;
    Sensors,
    Volume 22, Issue 14, pp. 5068, July 2022. DOI: 10.3390/s22145068
    
    Abstract: ...

    Clamp-on ultrasonic flow meters (UFMs) are installed on the outside of the pipe wall. Typically, they consist of two single-element transducers mounted on angled wedges, which are acoustically coupled to the pipe wall. Before flow metering, the transducers are placed at the correct axial position by manually moving one transducer along the pipe wall until the maximum amplitude of the relevant acoustic pulse is obtained. This process is time-consuming and operator-dependent. Next to this, at least five parameters of the pipe and the liquid need to be provided manually to compute the flow speed. In this work, a method is proposed to obtain the five parameters of the pipe and the liquid required to compute the flow speed. The method consists of obtaining the optimal angles for different wave travel paths by varying the steering angle of the emitted acoustic beam systematically. Based on these optimal angles, a system of equations is built and solved to extract the desired parameters. The proposed method was tested experimentally with a custom-made clamp-on UFM consisting of two linear arrays placed on a water-filled stainless steel pipe. The obtained parameters of the pipe and the liquid correspond very well with the expected (nominal) values. Furthermore, the performed experiment also demonstrates that a clamp-on UFM based on transducer arrays can achieve self-alignment without the need to manually move the transducers.

20. Smart Ultrasound Probes: Going Digital in the Probe Tip
    M. Pertijs;
    In IEEE Sensor Interfaces Meeting,
    2022. Keynote presentation.
    
    Abstract: ...

    While medical ultrasound imaging is currently mainly done using hand-held probes connected to relatively bulky imaging systems, various new application areas are emerging that call for advanced miniaturized ultrasound devices. Examples include catheters capable of providing real-time 3D images to guide minimally-invasive interventions, and wearable devices for new monitoring and diagnostic applications. In contrast with conventional probes, which contain little or no electronics, these new devices need to become “smart”: integrated circuits need to be integrated into the probe to interface with the many transducer elements (typically 1000+) needed for real-time 3D imaging. This talk discusses the challenges and opportunities associated with integrated circuit design for smart ultrasound probes, focusing on strategies for channel-count reduction and digitization that pave the way towards probes with fully-digital interfaces. The talk will include examples of state-of-the-art designs featuring transducer-on-CMOS integration and pitch-matched circuits for high-voltage pulsing, beamforming and digitization.

21. A Pitch-Matched ASIC with Integrated 65V TX and Shared Hybrid Beamforming ADC for Catheter-Based High-Frame-Rate 3D Ultrasound Probes
    Y. Hopf; B. Ossenkoppele; M. Soozande; E. Noothout; Z. Y. Chang; C. Chen; H. J. Vos; J. G. Bosch; M. D. Verweij; N. de Jong; M. A. P. Pertijs;
    In Dig. Techn. Papers IEEE International Solid-State Circuits Conference (ISSCC),
    February 2022. DOI: 10.1109/ISSCC42614.2022.9731597
    
    Abstract: ...

    With applications moving to 3D imaging, catheter-based ultrasound probes need to reach a new level of integration. This paper presents the first chip to combine high-voltage transmitters, analog front-ends, micro-beamforming, digitization and transducers, enabling high-frame-rate 3D imaging. Its pitch-matched architecture, made possible by a shared SAR/slope ADC that is 4x smaller and consumes 1.5x less power than the prior art, makes it a scalable solution for future digital imaging catheters.

22. A 1.2mW/channel 100μm-Pitch-Matched Transceiver ASIC with Boxcar-Integration-Based RX Micro-Beamformer for High-Resolution 3D Ultrasound Imaging
    P. Guo; F. Fool; E. Noothout; Z. Y. Chang; H. J. Vos; J. G. Bosch; M. D. Verweij; N. de Jong; M. A. P. Pertijs;
    In Dig. Techn. Papers IEEE International Solid-State Circuits Conference (ISSCC),
    February 2022. DOI: 10.1109/ISSCC42614.2022.9731784

23. Transceiver ASIC Design for High-Frame-Rate 3D Intracardiac Echocardiography
    Yannick M. Hopf; Boudewine Ossenkoppele; Mehdi Soozande; Emile Noothout; Zu-Yao Chang; Chao Chen; Hendrik J. Vos; Johan G. Bosch; Martin D. Verweij; Nico de Jong; Michiel A. P. Pertijs;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    2022.

24. Large Matrix array aperture for 3D vascular imaging capture
    Q. Colas; C. Bantignies; M. Perroteau; N. Porcher; S. Vassal; B. Guérif; T. Kim; J. G. Bosch; N. de Jong; M. D. Verweij; M. A. P. Pertijs; G. Férin; M. Flesch;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    2022.

25. A Pitch-Matched ASIC with Integrated 65V TX and Shared Hybrid Beamforming ADC for Catheter-Based High-Frame-Rate 3D Ultrasound Probes
    Yannick Hopf; Michiel Pertijs;
    In Annual Workshop on Circuits, Systems and Signal Processing (ProRISC),
    July 2022. Best presentation award.

26. Automated Characterization of Matrix Transducer Arrays using the Verasonics Imaging System
    Djalma Simoes dos Santos; Fabian Fool; Taehoon Kim; Emile Noothout; Nuriel Rozsa; Hendrik J. Vos; Johan G. Bosch; Michiel A. P. Pertijs; Martin D. Verweij; Nico de Jong;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    2022.

27. Automated Characterization of Matrix Transducer Arrays using the Verasonics Imaging System
    Djalma Simoes dos Santos; Fabian Fool; Taehoon Kim; Emile Noothout; Nuriel Rozsa; Hendrik J. Vos; Johan G. Bosch; Michiel A. P. Pertijs; Martin D. Verweij; Nico de Jong;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    2022.

28. Large Matrix array aperture for 3D vascular imaging capture
    Q. Colas; C. Bantignies; M. Perroteau; N. Porcher; S. Vassal; B. Guérif; T. Kim; J. G. Bosch; N. de Jong; M. D. Verweij; M. A. P. Pertijs; G. Férin; M. Flesch;
    In Smart Systems Integration Conference,
    2022. abstract.

29. Design of an Ultrasound Transceiver ASIC with a Switching-Artifact Reduction Technique for 3-D Carotid Artery Imaging
    T. Kim; F. Fool; D. Simoes dos Santos; Z. Y. Chang; E. Noothout; H. J. Vos; J. G. Bosch; M. D. Verweij; N. de Jong; M. A. P. Pertijs;
    Sensors,
    Volume 21, Issue 1, pp. 150, January 2021. DOI: 10.3390/s21010150
    
    Abstract: ...

    This paper presents an ultrasound transceiver application-specific integrated circuit (ASIC) directly integrated with an array of 12 × 80 piezoelectric transducer elements to enable next-generation ultrasound probes for 3D carotid artery imaging. The ASIC, implemented in a 0.18 µm high-voltage Bipolar-CMOS-DMOS (HV BCD) process, adopted a programmable switch matrix that allowed selected transducer elements in each row to be connected to a transmit and receive channel of an imaging system. This made the probe operate like an electronically translatable linear array, allowing large-aperture matrix arrays to be interfaced with a manageable number of system channels. This paper presents a second-generation ASIC that employed an improved switch design to minimize clock feedthrough and charge-injection effects of high-voltage metal–oxide–semiconductor field-effect transistors (HV MOSFETs), which in the first-generation ASIC caused parasitic transmissions and associated imaging artifacts. The proposed switch controller, implemented with cascaded non-overlapping clock generators, generated control signals with improved timing to mitigate the effects of these non-idealities. Both simulation results and electrical measurements showed a 20 dB reduction of the switching artifacts. In addition, an acoustic pulse-echo measurement successfully demonstrated a 20 dB reduction of imaging artifacts.
    
    document

30. A Readout IC for Capacitive Touch Screen Panels with 33.9 dB Charge-Overflow Reduction Using Amplitude-Modulated Multi-Frequency Excitation
    J.-S. An; J.-H. Ra; E. Kang; M. Pertijs; S.-H. Han;
    IEEE Journal of Solid-State Circuits,
    Volume 56, Issue 11, pp. 3486-3498, November 2021. DOI: 10.1109/JSSC.2021.3100470
    
    Abstract: ...

    This paper presents a readout integrated circuit (ROIC) for capacitive touch-screen panels employing an amplitude-modulated multiple-frequency excitation (AM-MFE) technique. To prevent charge overflow, which occurs periodically at the beat frequency of the excitation frequencies, the ROIC modulates the amplitude of the excitation voltages at a mixing frequency derived from the excitation frequencies. Thus, the ROIC can sense the charge signal without charge overflow and maximize the signal-to-noise ratio (SNR) by increasing the amplitude of the excitation voltages up to the sensing range of the readout circuit. The proposed ROIC was fabricated in a 0.13-µm standard CMOS process and was measured with a 32-inch 104×64 touch-screen panel using 1 mm and 10 mm metal pillars. It reduces charge overflow up to 33.9 dB compared to operation without AM-MFE. In addition, the ROIC achieves a frame rate of 2.93 kHz, and SNRs of 41.7 dB and 61.6 dB with 1 mm and 10 mm metal pillars, respectively.

31. A Transceiver ASIC for a Single-Cable 64-Element Intra-Vascular Ultrasound Probe
    D. van Willigen; J. Janjic; E. Kang; Z. Y. Chang; E. Noothout; M. Verweij; N. de Jong; M. Pertijs;
    IEEE Journal of Solid-State Circuits,
    Volume 56, Issue 10, pp. 3157-3166, October 2021. DOI: 10.1109/jssc.2021.3083217
    
    Abstract: ...

    This article presents an application-specific integrated circuit (ASIC) designed for intra-vascular ultrasound imaging that interfaces 64 piezoelectric transducer elements to an imaging system using a single micro-coaxial cable. Thus, it allows a single-element transducer to be replaced by a transducer array to enable 3-D imaging. The 1.5-mm-diameter ASIC is intended to be mounted at the tip of a catheter, directly integrated with a 2-D array of piezoelectric transducer elements. For each of these elements, the ASIC contains a high-voltage (HV) switch, allowing the elements to transmit an acoustic wave in response to an HV pulse generated by the imaging system. A low-noise amplifier then amplifies the resulting echo signals and relays them as a signal current to the imaging system, while the same cable provides a 3-V supply. Element selection and other settings can be programmed by modulating configuration data on the supply, thus enabling full synthetic aperture imaging. An integrated element test mode measures the element capacitance to detect bad connections to the transducer elements. The ASIC has been fabricated in a 0.18-μm HV CMOS technology and consumes only 6 mW in receive. Electrical measurements show correct switching of 30-V transmit pulses and a receive amplification with a 71-dB dynamic range, including 12 dB of programmable gain over a 3-dB bandwidth of 21 MHz. The functionality of the ASIC has been successfully demonstrated in a 3-D imaging experiment.

32. Exploiting nonlinear wave propagation to improve the precision of ultrasonic flow meters
    J. Massaad; P. L. M. J. van Neer; D. M. van Willigen; N. de Jong; M. A. P. Pertijs; M. D. Verweij;
    Ultrasonics,
    Volume 116, pp. 106476, September 2021. DOI: 10.1016/j.ultras.2021.106476

33. Integrated Transceivers for Emerging Medical Ultrasound Imaging Devices: A Review
    C. Chen; M. Pertijs;
    IEEE Open Journal of the Solid-State Circuits Society,
    Volume 1, pp. 104-114, September 2021. DOI: 10.1109/OJSSCS.2021.3115398

34. A Pitch-Matched Analog Front-End with Continuous Time-Gain Compensation for High-Density Ultrasound Transducer Arrays
    P. Guo; Z. Y. Chang; E. Noothout; H. J. Vos; J. Bosch; N. de Jong; M. D. Verweij; M. A. P. Pertijs;
    In Proc. European Solid-State Circuits Conference (ESSCIRC),
    pp. 163-166, September 2021.
    
    Abstract: ...

    This paper presents a compact programmable high-voltage (HV) pulser for ultrasound imaging, designed for driving capacitive micro-machined ultrasonic transducers (CMUTs) in miniature ultrasound probes. To enable bipolar return-to-zero pulsing and embedded transmit/receive switching, a compact back-to-back isolating HV switch is proposed that employs HV floating-gate drivers with only one HV MOS transistor each. The pulser can be digitally programmed to generate bipolar pulses with and without return-to-zero, with a peak-to-peak swing up to 60 V, as well as negative and positive unipolar pulses. It can generate bursts of up to 63 pulses, with a maximum pulse frequency of 9 MHz for an 18 pF transducer capacitance. Realized in TSMC 0.18 μm HV BCD technology, the pulser occupies only 0.167 mm2. Electrical characterization results of the pulser, as well as acoustic results obtained in combination with a 7.5-MHz CMUT transducer, are presented.

35. Experimental Investigation of the Effect of Subdicing on an Ultrasound Matrix Transducer
    D. Simoes dos Santos; F. Fool; T. Kim; E. Noothout; H. J. Vos; J. G. Bosch; M. A. P. Pertijs; M. D. Verweij; N. de Jong;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    September 2021. DOI: 10.1109/ius52206.2021.9593315
    
    Abstract: ...

    Over the past decades, real-time three-dimensional (3D) medical ultrasound has attracted much attention since it enables clinicians to diagnose more accurately. This calls for ultrasound matrix transducers with a large number of elements, which can be interfaced with an application-specific integrated circuit (ASIC) for data reduction. An important aspect of the design of such a transducer is the geometry of each element, since it affects the mode of vibration and, consequently, the efficiency of the transducer. In this paper, we experimentally investigate the effect of subdicing on a piezoelectric (PZT) transducer. We fabricate and acoustically characterize a prototype PZT matrix transducer built on top of ASICs. The prototype transducer contains subdiced and non-subdiced elements, whose performance can be directly compared under the same conditions. Measurement results show that subdiced elements have a better performance compared to non-subdiced ones. Subdicing increases the peak pressure by 25%, raises the bandwidth by 10% and reduces the ringing time by 25%.

36. Automatic beam alignment in a clamp-on ultrasonic flow meter based on array transducers
    J. Massaad; P. van Neer; D. van Willigen; N. de Jong; M. Pertijs; M. Verweij;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    September 2021. abstract.

37. Feasibility of measuring flow velocity profiles with array-based clamp-on ultrasonic flow meters
    D. van Willigen; P. van Neer; J. Massaad; N. de Jong; M. Verweij; M. Pertijs;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    September 2021. abstract.

38. A Compact Integrated High -Voltage Pulserfor 3D Miniature Ultrasound Probes
    Yannick Hopf; Mehdi Soozande; Boudewine Ossenkoppele; Hendrik J. Vos; Martin D. Verweij; Johan G. Bosch; Nico de Jong; Michiel A. P. Pertijs;
    In Annual Workshop on Circuits, Systems and Signal Processing (ProRISC),
    July 2021. poster.

39. A Low-Power Reconfigurable Transceiver ASIC for a CMUT-based Wearable Ultrasound Patch
    Mingliang Tan; Tim Hosman; Jae-Sung An; Zu-Yao Chang; Michiel Pertijs;
    In Annual Workshop on Circuits, Systems and Signal Processing (ProRISC),
    July 2021.

40. An Area-Efficient Continuous Time-Gain Compensation Amplifier for Ultrasound Application
    P. Guo; Z.Y. Chang; E. Noothout; H.J. Vos; J.G. Bosch; N. de Jong; M.D. Verweij; M.A.P. Pertijs;
    In Annual Workshop on Circuits, Systems and Signal Processing (ProRISC),
    July 2021. poster.

41. Impact of Bit Errors in Digitized RF Data on Ultrasound Image Quality
    Z. Chen; M. Soozande; H. Vos; J. Bosch; M. Verweij; N. de Jong; M. Pertijs;
    IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control,
    Volume 67, Issue 1, pp. 13-24, January 2020. DOI: 10.1109/TUFFC.2019.2937462
    
    Abstract: ...

    This paper quantitatively analyzes the impact of bit errors in digitized RF data on ultrasound image quality. The quality of B-mode images in both linear and phased array imaging is evaluated by means of three objective image quality metrics: peak signal-to-noise ratio, structural similarity index and contrast-to-noise ratio, when bit errors are introduced to the RF data with different bit-error rates (BERs). The effectiveness of coding schemes for forward error detection and correction to improve the image quality is also studied. The results show that ultrasound imaging is inherently resilient to high BER. The image quality suffers unnoticeable degradation for BER lower than 1E-6. Simple 1-bit parity coding with 9% added redundancy helps to retain similar image quality for BER up to 1E-4, and Hamming coding with 33.3% added redundancy allows the BER to increase to 1E-3. These results can serve as a guideline in the datalink design for ultrasound probes with in-probe receive digitization. With much more relaxed BER requirements than in typical datalinks, the design can be optimized by allowing fewer cables with higher data rate per cable or lower power consumption with the same cable count.

42. An Algorithm to Minimize the Zero-Flow Error in Transit-Time Ultrasonic Flow Meters
    Douwe M. van Willigen; Paul L.M.J. van Neer; Jack Massaad; Nico de Jong; Martin D. Verweij; Michiel A.P. Pertijs;
    IEEE Transactions on Instrumentation and Measurement,
    2020. DOI: 10.1109/TIM.2020.3007907
    
    Abstract: ...

    Transit-time ultrasonic flow meters are widely used in industry to measure fluid flow. In practice ultrasonic flow meters either show a zero-flow error or suffer from a significant random error due to a limited signal-to-noise ratio, requiring a significant amount of averaging to achieve good precision. This work presents a method that minimizes the zero-flow error whilst keeping the random error low, independent of the hardware used. The proposed algorithm can adjust to changing zero-flow errors while a flow is present. The technique combines the benefits of two common methods of determining the transit-time difference between the upstream and downstream ultrasonic waves: cross-correlation and zero-crossing detection. The algorithm is verified experimentally using a flow-loop. It is shown that the zero-flow error can be greatly reduced without compromising the random error or increasing circuit complexity.

43. A 64-Channel Transmit Beamformer with ±30V Bipolar High-Voltage Pulsers for Catheter-Based Ultrasound Probes
    M. Tan; E. Kang; J.-S. An; Z. Y. Chang; P. Vince; T. Matéo; N. Sénégond; M. A. P. Pertijs;
    IEEE Journal of Solid-State Circuits,
    Volume 55, Issue 7, pp. 1796-1806, July 2020. DOI: 10.1109/JSSC.2020.2987719
    
    Abstract: ...

    This article presents a fully integrated 64-channel programmable ultrasound transmit beamformer for catheter-based ultrasound probes, designed to interface with a capacitive micro-machined ultrasound transducer (CMUT) array. The chip is equipped with programmable high-voltage (HV) pulsers that can generate ±30-V return-to-zero (RZ) and non-RZ pulses. The pulsers employ a compact back-to-back isolating HV switch topology that employs HV floating-gate drivers with only one HV MOS transistor each. Further die-size reduction is achieved by using the RZ switches also as the transmit/receive (T/R) needed to pass received echo signals to low-voltage receive circuitry. On-chip digital logic clocked at 200 MHz allows the pulse timing to be programmed with a resolution of 5 ns, while supporting pulses of 1 cycle up to 63 cycles. The chip has been implemented in 0.18-μm HV Bipolar-CMOS-DMOS (BCD) technology and occupies an area of 1.8 mm x 16.5 mm, suitable for integration into an 8-F catheter. Each pulser with embedded T/R switch and digital logic occupies only 0.167 mm². The pulser successfully drives an 18-pF transducer capacitance at pulse frequencies up to 9 MHz. The T/R switch has a measured ON-resistance of ~180 Ω . The acoustic results obtained in combination with a 7.5-MHz 64-element CMUT array demonstrate the ability to generate steered and focused acoustic beams.

44. Suppression of Lamb wave excitation via aperture control of a transducer array for ultrasonic clamp-on flow metering
    J. Massaad; P. L. M. J. van Neer; D. M. van Willigen; M. A. P. Pertijs; N. de Jong; M. D. Verweij;
    Journal of the Acoustical Society of America,
    Volume 147, Issue 4, pp. 2670-2681, February 2020. DOI: 10.1121/10.0001135
    
    Abstract: ...

    During ultrasonic clamp-on flow metering, Lamb waves propagating in the pipe wall may limit the measurement accuracy by introducing absolute errors in the flow estimates. Upon reception, these waves can interfere with the up and downstream waves refracting from the liquid, and disturb the measurement of the transit time difference that is used to obtain the flow speed. Thus, suppression of the generation of Lamb waves might directly increase the accuracy of a clamp-on flow meter. Existing techniques apply to flow meters with single element transducers. This paper considers the application of transducer arrays and presents a method to achieve a predefined amount of suppression of these spurious Lamb waves based on appropriate amplitude weightings of the transducer elements. Finite element simulations of an ultrasonic clamp-on flow measurement setting will be presented to show the effect of array aperture control on the suppression of the Lamb waves in a 1-mm-thick stainless steel pipe wall. Furthermore, a proof-of-principle experiment will be shown that demonstrates a good agreement with the simulations.

45. Towards a calibration-free ultrasonic clamp-on flow meter: Pipe geometry measurements using matrix arrays
    J. Massaad; P. L. M. J. van Neer; D. M. van Willigen; M. A. P. Pertijs; N. de Jong; M. D. Verweij;
    Proceedings of Meetings on Acoustics,
    Volume 39, Issue 1, February 2020. DOI: 10.1121/2.0001187
    
    Abstract: ...

    Current ultrasonic clamp-on flow meters are manually calibrated. This process is based on manual placement of two single-element transducers along a pipe wall. Due to the usually unknown pipe properties and inhomogeneities in the pipe geometry, the axial distance of the transducers needs to be manually calibrated to align the location of the emitted beam on the receiver. In this work it is presented an automatic calibration procedure, based on matrix transducer arrays, to provide calibration information that would normally be entered into the instrument manually prior to ultrasonic clamp-on flow measurements. The calibration consists of two steps: First, along the axial direction of the pipe, Lamb waves are excited and recorded. Then, the measured time signals are combined with the Rayleigh-Lamb dispersion equation to extract pipe wall thickness and bulk wave sound speeds. Second, along the circumferential direction of the pipe, a specific Lamb wave mode is excited and recorded, from which the pipe diameter is estimated. The potential of both calibration procedures is shown, and the necessity of a matrix transducer array (i.e. small elements) is highlighted.

46. An Algorithm to Minimize the Zero-Flow Error in Transit-Time Ultrasonic Flow Meters
    D. M. van Willigen; P. L. M. J. van Neer; J. Massaad; N. de Jong; M. D. Verweij; M. A. P. Pertijs;
    IEEE Transactions on Instrumentation and Measurement,
    Volume 70, pp. 1-9, July 2020. DOI: 10.1109/TIM.2020.3007907
    
    Abstract: ...

    Transit-time ultrasonic flowmeters are widely used in industry to measure fluid flow. In practice, ultrasonic flowmeters either show a zero-flow error or suffer from a significant random error due to a limited signal-to-noise ratio, requiring a significant amount of averaging to achieve good precision. This work presents a method that minimizes the zero-flow error while keeping the random error low, independent of the hardware used. The proposed algorithm can adjust to changing zero-flow errors, while a flow is present. The technique combines the benefits of two common methods of determining the transit time difference between the upstream and downstream ultrasonic waves: cross correlation and zero-crossing detection. The algorithm is verified experimentally using a flow loop. It is shown that the zero-flow error can be greatly reduced without compromising the random error or increasing circuit complexity.

47. Receive/Transmit Aperture Selection for 3D Ultrasound Imaging with a 2D Matrix Transducer
    M. Mozaffarzadeh; M. Soozande; F. Fool; M. A. P. Pertijs; H. J. Vos; M. D. Verweij; J. G. Bosch; N. de Jong;
    MDPI Applied Sciences,
    Volume 10, Issue 15, July 2020. DOI: 10.3390/app10155300
    
    Abstract: ...

    Recently, we realized a prototype matrix transducer consisting of 48 rows of 80 elements on top of a tiled set of Application Specific Integrated Circuits (ASICs) implementing a row-level control connecting one transmit/receive channel to an arbitrary subset of elements per row. A fully sampled array data acquisition is implemented by a column-by-column (CBC) imaging scheme (80 transmit-receive shots) which achieves 250 volumes/second (V/s) at a pulse repetition frequency of 20 kHz. However, for several clinical applications such as carotid pulse wave imaging (CPWI), a volume rate of 1000 per second is needed. This allows only 20 transmit-receive shots per 3D image. In this study, we propose a shifting aperture scheme and investigate the effects of receive/transmit aperture size and aperture shifting step in the elevation direction. The row-level circuit is used to interconnect elements of a receive aperture in the elevation (row) direction. An angular weighting method is used to suppress the grating lobes caused by the enlargement of the effective elevation pitch of the array, as a result of element interconnection in the elevation direction. The effective aperture size, level of grating lobes, and resolution/sidelobes are used to select suitable reception/transmission parameters. Based on our assessment, the proposed imaging sequence is a full transmission (all 80 elements excited at the same time), a receive aperture size of 5 and an aperture shifting step of 3. Numerical results obtained at depths of 10, 15, and 20 mm show that, compared to the fully sampled array, the 1000 V/s is achieved at the expense of, on average, about two times wider point spread function and 4 dB higher clutter level. The resulting grating lobes were at −27 dB. The proposed imaging sequence can be used for carotid pulse wave imaging to generate an informative 3D arterial stiffness map, for cardiovascular disease assessment.

48. A Variable-Gain Low-Noise Transimpedance Amplifier for Miniature Ultrasound Probes
    E. Kang; M. Tan; J. S. An; Z. Y. Chang; P. Vince; N. Sénégond; T. Mateo; C. Meynier; M. A. P. Pertijs;
    IEEE Journal of Solid-State Circuits,
    Volume 55, Issue 12, pp. 3157--3168, December 2020. DOI: 10.1109/jssc.2020.3023618
    
    Abstract: ...

    This article presents a low-noise transimpedance amplifier (TIA) designed for miniature ultrasound probes. It provides continuously variable gain to compensate for the time-dependent attenuation of the received echo signal. This time-gain compensation (TGC) compresses the echo-signal dynamic range (DR) while avoiding imaging artifacts associated with discrete gain steps. Embedding the TGC function in the TIA reduces the output DR, saving power compared to prior solutions that apply TGC after the low-noise amplifier. The TIA employs a capacitive ladder feedback network and a current-steering circuit to obtain a linear-in-dB gain range of 37 dB. A variable-gain loop amplifier based on current-reuse stages maintains constant bandwidth in a power-efficient manner. The TIA has been integrated in a 64-channel ultrasound transceiver application-specific integrated circuit (ASIC) in a 180-nm BCDMOS process and occupies a die area of 0.12 mm². It achieves a gain error below ±1 dB and a 1.7 pA/√ Hz noise floor and consumes 5.2 mW from a ±0.9 V supply. B-mode images of a tissue-mimicking phantom are presented that show the benefits of the TGC scheme.

49. A Capacitive Touch Chipset with 33.9dB Charge-Overflow Reduction using Amplitude-Modulated Multi-Frequency Excitation and Wireless Power and Data Transfer to an Active Stylus
    J.-S. An; J.-H. Ra; E. Kang; M. Pertijs; S.-H. Han;
    In Dig. Techn. Papers IEEE International Solid-State Circuits Conference (ISSCC),
    pp. 430-431, February 2020.

50. A 2 pA/√Hz Transimpedance Amplifier for Miniature Ultrasound Probes with 36dB Continuous Time-Gain Compensation
    E. Kang; M. Tan; J. An; P. Vince; N. Sénégond; T. Mateo; Cyril Meynier; M. A. P. Pertijs;
    In Dig. Techn. Papers IEEE International Solid-State Circuits Conference (ISSCC),
    pp. 354-355, February 2020.

51. Experimental Characterization of a Linear Transducer Array Prototype for Ultrasonic Clamp-on Flow Metering
    J. Massaad; D. van Willigen; P. van Neer; E. Noothout; N. de Jong; M. Pertijs; M. Verweij;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    September 2020. abstract.

52. Energy Consumption Model for Front-End Electronics of Battery-Powered Ultrasound Devices
    M. Tan; M. Pertijs;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    September 2020. abstract.

53. A 12×80 Element Ultrasound Transceiver ASIC With Enhanced Charge Injection Performance for 3-D Carotid Artery Imaging
    T. Kim; F. Fool; E. Kang; Z. Y. Chang; E. Noothout; J. G. Bosch; M. D. Verweij; N. de Jong; M. Pertijs;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    September 2020. abstract.

54. Integrated Front-End Electronics for Miniature Ultrasound Probes
    M. Pertijs;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    September 2020. invited paper.

55. A 1-D CMUT Transducer with Front-end ASIC in a 9 French Catheter for Intracardiac Echocardiography: Acoustic and Imaging Evaluation
    T. Matéo; P. Vince; N. Sénégond; M. Tan; E. Kang; M. Pertijs;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    September 2020. DOI: 10.1109/IUS46767.2020.9251715
    
    Abstract: ...

    In this work, we report the acoustical characterization of a 9 French (Fr) CMUT-based 1D catheter tip (2.5×12.8 mm2 - 64 elements - 7.5 MHz) embedding a 64 channels analog transceiver ASIC (180 nm HV BCD technology) dedicated to Intra-cardiac Echocardiography. To this end, a Through-Silicon-Via process has been integrated in the CMUT process flow to ensure suitable vertical integration level needed to accommodate with the catheter's form factor. Good overall functioning of essential ASIC functionalities with the CMUT, i.e. transmit, beamforming, and receive, is first reported, starting from elementary characterization up to imaging. Additionally, a comparison with a custom discrete solution based on Commercial Off-The-Shelf components (COTS) to provide suitable CMUT preamplification in receive is performed. Using the same CMUT chip either with the ASIC, either with the COTS, allowed to quantify the benefit brought by the ASIC compared to a more straightforward but less integrated solution. Main results highlight that CMUT-on-ASIC allows to recover a much wider bandwidth (BW), increasing by 3 MHz the -6dB upper limit, and therefore getting closer the theoretical BW of the CMUT itself. Moreover, lower element crosstalk is measured on CMUT-on-ASIC device, showing that the ASIC decreases the electrical coupling compared to the COTS. Finally, noise equivalent pressure measurements in comparison with simulations in realistic ICE configuration promise much higher receive sensitivity with the ASIC solution, hence, confirming its great interest for the CMUT technology compared to less integrated solution, especially for catheter application.

56. 3D High Frame Rate Imaging Scheme for Ultrasound Carotid Imaging
    M. Soozande; M. Mozzaffarzadeh; F. Fool; T. Kim; E. Kang; M. Pertijs; M. Verweij; H. J. Vos; J. G. Bosch; N. de Jong;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    September 2020. abstract.

57. Capacitance-to-digital converter
    H. Fan; M. Pertijs; B. A. J. Buter;
    Patent, US 10,732,577, August 2020.

58. Miniaturized Broadband Microwave Permittivity Sensing for Biomedical Applications
    G. Vlachogiannakis; Z. Hu; H. T. Shivamurthy; A. Neto; M. A. P. Pertijs; M. Spirito; L. C. N. de Vreede;
    IEEE Journal of Electromagnetics, RF and Microwaves in Medicine and Biology,
    Volume 3, Issue 1, pp. 48--55, March 2019. DOI: 10.1109/JERM.2018.2882564
    
    Abstract: ...

    A compact sensing pixel for the determination of the localized complex permittivity at microwave frequencies is proposed. Implemented in the 40-nm CMOS, the architecture comprises a square patch, interfaced to the material-under-test sample, that provides permittivity-dependent admittance. The patch admittance is read out by embedding the patch in a double-balanced, RF-driven Wheatstone bridge. The bridge is cascaded by a linear, low-intermediate frequency switching downconversion mixer, and is driven by a square wave that allows simultaneous characterization of multiple harmonics, thus increasing measurement speed and extending the frequency range of operation. In order to allow complex permittivity measurement, a calibration procedure has been developed for the sensor. Measurement results of liquids show good agreement with theoretical values, and the measured relative permittivity resolution is better than 0.3 over a 0.1-10-GHz range. The proposed implementation features a measurement speed of 1 ms and occupies an active area of 0.15x0.3 mm², allowing for future compact arrays of multiple sensors that facilitate 2-D dielectric imaging based on permittivity contrast.

59. An Integrated Programmable High-Voltage Bipolar Pulser with Embedded Transmit/Receive Switch for Miniature Ultrasound Probes
    M. Tan; E. Kang; J.-S. An; Z. Y. Chang; P. Vince; N. Sénégond; M. A. P. Pertijs;
    IEEE Solid-State Circuits Letters,
    Volume 2, Issue 9, pp. 79-82, September 2019. DOI: 10.1109/LSSC.2019.2938141
    
    Abstract: ...

    This letter presents a compact programmable high-voltage (HV) pulser for ultrasound imaging, designed for driving capacitive micromachined ultrasonic transducers (CMUTs) in miniature ultrasound probes. To enable bipolar return-to-zero (RZ) pulsing and embedded transmit/receive switching, a compact back-to-back isolating HV switch is proposed that employs HV floating-gate drivers with only one HV MOS transistor each. The pulser can be digitally programmed to generate bipolar pulses with and without RZ, with a peak-to-peak swing up to 60 V, as well as negative and positive unipolar pulses. It can generate bursts of up to 63 pulses, with a maximum pulse frequency of 9 MHz for an 18-pF transducer capacitance. Realized in TSMC 0.18um HV BCD technology, the pulser occupies only 0.167mm2 . Electrical characterization results of the pulser, as well as acoustic results obtained in the combination with a 7.5-MHz CMUT transducer, are presented.

60. CMOS-Compatible Carbon Dioxide Sensors
    Cai, Zeyu; van Veldhoven, Robert; Suy, Hilco; de Graaf, Ger; Makinwa, Kofi A. A.; Pertijs, Michiel;
    Makinwa, Kofi A. A.; Baschirotto, Andrea; Harpe, Pieter (Ed.);
    Cham: Springer International Publishing, , pp. 199--219, 2019. DOI: 10.1007/978-3-319-97870-3_11
    
    Abstract: ...

    This chapter presents two cost-effective sensors that measure ambient carbon dioxide (CO2) concentration, intended for application in smart ventilation systems in buildings or in mobile devices. Both sensors employ a suspended hot-wire transducer to detect the CO2-dependent thermal conductivity (TC) of the ambient air. The resistive transducer is realized in the VIA layer of a standard CMOS process using a single etch step. The first sensor determines the transducer's CO2-dependent thermal resistance to the surrounding air by measuring its steady-state temperature rise and power dissipation. A ratiometric measurement is realized by employing an identical but capped transducer as a reference. An incremental delta-sigma ADC digitizes the temperature and power ratios of the transducers, from which the ratio of the thermal resistances is calculated. The second sensor is based on a transient measurement of the CO2-dependent thermal time constant of the transducer. The readout circuit periodically heats up the transducer and uses a phase-domain delta-sigma modulator to digitize the CO2-dependent phase shift of the resulting temperature transients. Compared to the ratiometric steady-state measurement, this approach significantly reduces the measurement time and improves the energy efficiency, resulting in a state-of-the-art CO2 resolution of 94 ppm at an energy consumption of 12 mJ per measurement.

61. Feasibility of High Frame Rate 3-D Intracardiac Echography using Fan-Beam Transmissions
    M. Soozande; B. Ossenkoppele; Y. Hopf; M. A. P. Pertijs; M. D. Verweij; H. J. Vos; J. G. Bosch; N. de Jong;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    IEEE, pp. 1-4, October 2019.

62. Fabrication and characterization of a prototype forward-looking single-cable 64-element intra-vascular ultrasound probe
    D. van Willigen; M. Mozaffarzadeh; E. Noothout; M. Verweij; N. de Jong; M. Pertijs; V. Daeichin;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    IEEE, pp. 1-4, October 2019.

63. 3D high frame rate flow measurement using a prototype matrix transducer for carotid imaging
    F. Fool; H. J. Vos; M. Shabanimotlagh; T. Kim; E. Kang; M. Pertijs; N. de Jong; M. D. Verweij;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    IEEE, pp. 1-4, October 2019.

64. A 1.54mW/Element 150μm-Pitch-Matched Receiver ASIC with Element-Level SAR/Shared-Single-Slope Hybrid ADCs for Miniature 3D Ultrasound Probes
    J. Li; Z. Chen; M. Tan; D. van Willigen; C. Chen; Z. Y. Chang; E. Noothout; N. de Jong; M. D. Verweij; M. A. P. Pertijs;
    In Dig. Techn. Paper IEEE Symposium on VLSI Circuits (VLSI),
    IEEE, pp. 1-2, June 2019.

65. Acoustic Stack Design of a Transducer Array for Ultrasonic Clamp-on Flow Metering
    J. Massaad; D. van Willigen; P. van Neer; N. de Jong; M. Pertijs; M. Verweij;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    IEEE, pp. 1-4, October 2019.

66. Pipe geometry calibration measurements for the improvement of ultrasonic clamp-on flow meters
    J. Massaad; D. van Willigen; P. van Neer; N. de Jong; M. Pertijs; M. Verweij;
    In Meeting of the Acoustical Society of America,
    November 2019. (abstract),. DOI: 10.1121/1.5136993

67. An Integrated Programmable High-Voltage Bipolar Pulser with Embedded Transmit/Receive Switch for Miniature Ultrasound Probes
    M. Tan; E. Kang; J.-S. An; Z. Y. Chang; P. Vince; N. Sénégond; M. A. P. Pertijs;
    In Proc. European Solid-State Circuits Conference (ESSCIRC),
    pp. 325--328, October 2019.
    
    Abstract: ...

    This paper presents a compact programmable high-voltage (HV) pulser for ultrasound imaging, designed for driving capacitive micro-machined ultrasonic transducers (CMUTs) in miniature ultrasound probes. To enable bipolar return-to-zero pulsing and embedded transmit/receive switching, a compact back-to-back isolating HV switch is proposed that employs HV floating-gate drivers with only one HV MOS transistor each. The pulser can be digitally programmed to generate bipolar pulses with and without return-to-zero, with a peak-to-peak swing up to 60 V, as well as negative and positive unipolar pulses. It can generate bursts of up to 63 pulses, with a maximum pulse frequency of 9 MHz for an 18 pF transducer capacitance. Realized in TSMC 0.18 μm HV BCD technology, the pulser occupies only 0.167 mm2. Electrical characterization results of the pulser, as well as acoustic results obtained in combination with a 7.5-MHz CMUT transducer, are presented.

68. A Low-Power ASIC with On-Chip Receive Digitization and Bipolar High-Voltage Transmitters for Wearable Ultrasound Devices
    Jae-Sung An; Mingliang Tan; Michiel Pertijs;
    In Annual Workshop on Circuits, Systems and Signal Processing (ProRISC),
    July 2019. poster.

69. Amplifier with continuous gain control
    M. A. P. Pertijs; E. Kang;
    Patent, WO2021/015618A2, July 2019.

70. A 40-nm CMOS Complex Permittivity Sensing Pixel for Material Characterization at Microwave Frequencies
    G. Vlachogiannakis; M. A. P. Pertijs; M. Spirito; L. C. N. de Vreede;
    IEEE Transactions on Microwave Theory and Techniques,
    Volume 66, Issue 3, pp. 1619-1634, March 2018. DOI: 10.1109/tmtt.2017.2753228
    
    Abstract: ...

    A compact sensing pixel for the determination of the localized complex permittivity at microwave frequencies is proposed. Implemented in the 40-nm CMOS, the architecture comprises a square patch, interfaced to the material-under-test sample, that provides permittivity-dependent admittance. The patch admittance is read out by embedding the patch in a double-balanced, RF-driven Wheatstone bridge. The bridge is cascaded by a linear, low-intermediate frequency switching downconversion mixer, and is driven by a square wave that allows simultaneous characterization of multiple harmonics, thus increasing measurement speed and extending the frequency range of operation. In order to allow complex permittivity measurement, a calibration procedure has been developed for the sensor. Measurement results of liquids show good agreement with theoretical values, and the measured relative permittivity resolution is better than 0.3 over a 0.1-10-GHz range. The proposed implementation features a measurement speed of 1 ms and occupies an active area of 0.15x0.3 mm², allowing for future compact arrays of multiple sensors that facilitate 2-D dielectric imaging based on permittivity contrast.

71. Multiline 3D beamforming using micro-beamformed datasets for pediatric transesophageal echocardiography
    D. Bera; S. B. Raghunathan; C. Chen; Z. Chen; M. A. P. Pertijs; M. D. Verweij; V. Daeichin; H. J. Vos; A. F. W. van der Steen; N. de Jong; J. G. Bosch;
    Physics in Medicine \& Biology,
    Volume 63, Issue 7, pp. 1-16, March 2018. DOI: 10.1088/1361-6560/aab45e
    
    Abstract: ...

    Until now, no matrix transducer has been realized for 3D transesophageal echocardiography (TEE) in pediatric patients. In 3D TEE with a matrix transducer, the biggest challenges are to connect a large number of elements to a standard ultrasound system, and to achieve a high volume rate (>200 Hz). To address these issues, we have recently developed a prototype miniaturized matrix transducer for pediatric patients with micro-beamforming and a small central transmitter. In this paper we propose two multiline parallel 3D beamforming techniques (µBF25 and µBF169) using the micro-beamformed datasets from 25 and 169 transmit events to achieve volume rates of 300 Hz and 44 Hz, respectively. Both the realizations use angle-weighted combination of the neighboring overlapping sub-volumes to avoid artifacts due to sharp intensity changes introduced by parallel beamforming. In simulation, the image quality in terms of the width of the point spread function (PSF), lateral shift invariance and mean clutter level for volumes produced by µBF25 and µBF169 are similar to the idealized beamforming using a conventional single-line acquisition with a fully-sampled matrix transducer (FS4k, 4225 transmit events). For completeness, we also investigated a 9 transmit-scheme (3  ×  3) that allows even higher frame rates but found worse B-mode image quality with our probe. The simulations were experimentally verified by acquiring the µBF datasets from the prototype using a Verasonics V1 research ultrasound system. For both µBF169 and µBF25, the experimental PSFs were similar to the simulated PSFs, but in the experimental PSFs, the clutter level was ~10 dB higher. Results indicate that the proposed multiline 3D beamforming techniques with the prototype matrix transducer are promising candidates for real-time pediatric 3D TEE.

72. A Reconfigurable Ultrasound Transceiver ASIC With 24 × 40 Elements for 3D Carotid Artery Imaging
    E. Kang; Q. Ding; M. Shabanimotlagh; P. Kruizinga; Z. Y. Chang; E. Noothout; H. J. Vos; J. G. Bosch; M. D. Verweij; N. de Jong; M. A. P. Pertijs;
    IEEE Journal of Solid-State Circuits,
    Volume 53, Issue 7, pp. 2065-2075, July 2018. DOI: 10.1109/JSSC.2018.2820156
    
    Abstract: ...

    This paper presents an ultrasound transceiver application-specific integrated circuit (ASIC) designed for 3-D ultrasonic imaging of the carotid artery. This application calls for an array of thousands of ultrasonic transducer elements, far exceeding the number of channels of conventional imaging systems. The 3.6 x 6.8 mm² ASIC interfaces a piezo-electric transducer (PZT) array of 24 x 40 elements, directly integrated on top of the ASIC, to an imaging system using only 24 transmit and receive channels. Multiple ASICs can be tiled together to form an even bigger array. The ASIC, implemented in a 0.18 μm high-voltage (HV) BCD process, consists of a reconfigurable switch matrix and row-level receive circuits. Each element is associated with a compact bootstrapped HV transmit switch, an isolation switch for the receive circuits and programmable logic that enables a variety of imaging modes. Electrical and acoustic experiments successfully demonstrate the functionality of the ASIC. In addition, the ASIC has been successfully used in a 3-D imaging experiment.

73. Fast volumetric imaging using a matrix TEE probe with partitioned transmit-receive array
    D. Bera; F. van den Adel; N. Radeljic-Jakic; B. Lippe; M. Soozande; M. A. P. Pertijs; M. D. Verweij; P. Kruizinga; V. Daeichin; H. J. Vos; A. F. W. van der Steen; J. G. Bosch; N. de Jong;
    Ultrasound in Medicine \& Biology,
    Volume 44, Issue 9, pp. 2025-2042, July 2018. DOI: 10.1016/j.ultrasmedbio.2018.05.017
    
    Abstract: ...

    We describe a 3-D multiline parallel beamforming scheme for real-time volumetric ultrasound imaging using a prototype matrix transesophageal echocardiography probe with diagonally diced elements and separated transmit and receive arrays. The elements in the smaller rectangular transmit array are directly wired to the ultrasound system. The elements of the larger square receive aperture are grouped in 4 × 4-element sub-arrays by micro-beamforming in an application-specific integrated circuit. We propose a beamforming sequence with 85 transmit–receive events that exhibits good performance for a volume sector of 60° × 60°. The beamforming is validated using Field II simulations, phantom measurements and in vivo imaging. The proposed parallel beamforming achieves volume rates up to 59 Hz and produces good-quality images by angle-weighted combination of overlapping sub-volumes. Point spread function, contrast ratio and contrast-to-noise ratio in the phantom experiment closely match those of the simulation. In vivo 3-D imaging at 22-Hz volume rate in a healthy adult pig clearly visualized the cardiac structures, including valve motion.

74. A Front-End ASIC with High-Voltage Transmit Switching and Receive Digitization for 3D Forward-Looking Intravascular Ultrasound Imaging
    M. Tan; C. Chen; Z. Chen; J. Janjic; V. Daeichin; Z. Y. Chang; E. Noothout; G. van Soest; M. D. Verweij; N. de Jong; M. A. P. Pertijs;
    IEEE Journal of Solid-State Circuits,
    Volume 53, Issue 8, pp. 2284-2297, August 2018. DOI: 10.1109/JSSC.2018.2828826
    
    Abstract: ...

    This paper presents an area- and power-efficient application-specified integrated circuit (ASIC) for 3-D forward-looking intravascular ultrasound imaging. The ASIC is intended to be mounted at the tip of a catheter, and has a circular active area with a diameter of 1.5 mm on the top of which a 2-D array of piezoelectric transducer elements is integrated. It requires only four micro-coaxial cables to interface 64 receive (RX) elements and 16 transmit (TX) elements with an imaging system. To do so, it routes high-voltage (HV) pulses generated by the system to selected TX elements using compact HV switch circuits, digitizes the resulting echo signal received by a selected RX element locally, and employs an energy-efficient load-modulation datalink to return the digitized echo signal to the system in a robust manner. A multi-functional command line provides the required sampling clock, configuration data, and supply voltage for the HV switches. The ASIC has been realized in a 0.18-μm HV CMOS technology and consumes only 9.1 mW. Electrical measurements show 28-V HV switching and RX digitization with a 16-MHz bandwidth and 53-dB dynamic range. Acoustical measurements demonstrate successful pulse transmission and reception. Finally, a 3-D ultrasound image of a three-needle phantom is generated to demonstrate the imaging capability.

75. Acoustic characterization of a miniature matrix transducer for pediatric 3D transesophageal echocardiography
    V. Daeichin; D. Bera; S. Raghunathan; M. ShabaniMotlagh; Z. Chen; C. Chen; E. Noothout; H. J. Vos; M. Pertijs; J. Bosch; N. de Jong; M. Verweij;
    Ultrasound in Medicine \& Biology,
    Volume 44, Issue 10, pp. 2143-2154, October 2018. DOI: 10.1016/j.ultrasmedbio.2018.06.009
    
    Abstract: ...

    This paper presents the design, fabrication and characterization of a miniature PZT-on-CMOS matrix transducer for real-time pediatric 3-dimensional (3D) transesophageal echocardiography (TEE). This 3D TEE probe consists of a 32 × 32 array of PZT elements integrated on top of an Application Specific Integrated Circuit (ASIC). We propose a partitioned transmit/receive array architecture wherein the 8 × 8 transmitter elements, located at the centre of the array, are directly wired out and the remaining receive elements are grouped into 96 sub-arrays of 3 × 3 elements. The echoes received by these sub-groups are locally processed by micro-beamformer circuits in the ASIC that allow pre-steering up to ±37°. The PZT-on-CMOS matrix transducer has been characterized acoustically and has a centre frequency of 5.8 MHz, -6 dB bandwidth of 67%, a transmit efficiency of 6 kPa/V at 30 mm, and a receive dynamic range of 85 dB with minimum and maximum detectable pressures of 5 Pa and 84 kPa respectively. The properties are very suitable for a miniature pediatric real-time 3D TEE probe.

76. A Phase-Domain Readout Circuit for a CMOS-Compatible Hot-Wire CO$_2$ Sensor
    Z. Cai; R. van Veldhoven; H. Suy; G. de Graaf; K. Makinwa; M. Pertijs;
    IEEE Journal of Solid-State Circuits,
    Volume 53, Issue 11, pp. 3303--3313, November 2018. DOI: 10.1109/JSSC.2018.2866374
    
    Abstract: ...

    This paper presents a readout circuit for a carbon dioxide (CO2) sensor that measures the CO2-dependent thermal time constant of a hot-wire transducer. The readout circuit periodically heats up the transducer and uses a phase-domain modulator to digitize the phase shift of the resulting temperature transients. A single resistive transducer is used both as a heater and as a temperature sensor, thus greatly simplifying its fabrication. To extract the transducer’s resistance, and hence its temperature, in the presence of large heating currents, a pair of transducers is configured as a differentially driven bridge. The transducers and the readout circuit have been implemented in a standard 0.16-μm CMOS technology, with an active area of 0.3 and 3.14 mm2, respectively. The sensor consumes 6.8 mW from a 1.8-V supply, of which 6.3 mW is dissipated in the transducers. A resolution of 94-ppm CO2 is achieved in a 1.8-s measurement time, which corresponds to an energy consumption of 12 mJ per measurement, >10× less than prior CO2 sensors in CMOS technology.

77. An Element-Matched Electro-Mechanical ΔΣ ADC for Ultrasound Imaging
    M. D'Urbino; C. Chen; Z. Chen; Z. Y. Chang; J. Ponte; B. Lippe; M. Pertijs;
    IEEE Journal of Solid-State Circuits,
    Volume 53, Issue 10, pp. 2795-2805, October 2018. DOI: 10.1109/JSSC.2018.2859961
    
    Abstract: ...

    This paper presents a power- and area-efficient approach to digitizing the echo signals received by piezoelectric transducer elements, commonly used for ultrasound imaging. This technique utilizes such elements not only as sensors but also as the loop filter of an element-level Δ Σ analog to digital converter (ADC). The receiver chain is thus greatly simplified, yielding savings in area and power. Every ADC becomes small enough to fit underneath a 150 μ m x 150 μ m transducer element, enabling simultaneous acquisition and digitization from all the elements in a 2-D array. This is especially valuable for miniature 3-D probes. Experimental results are reported for a prototype receiver chip with an array of 5 x 4 element-matched ADCs and a transducer array fabricated on top of the chip. Each ADC consumes 800 μ W from a 1.8 V supply and achieves a SNR of 47 dB in a 75% bandwidth around a center frequency of 5 MHz.

78. A Pitch-Matched Front-End ASIC with Integrated Subarray Beamforming ADC for Miniature 3-D Ultrasound Probes
    C. Chen; Z. Chen; D. Bera; E. Noothout; Z. Y. Chang; M. Tan; H. Vos; J. Bosch; M. Verweij; N. de Jong; M. Pertijs;
    IEEE Journal of Solid-State Circuits,
    Volume 53, Issue 11, pp. 3050-3064, November 2018. DOI: 10.1109/JSSC.2018.2864295
    
    Abstract: ...

    This paper presents a front-end application-specified integrated circuit (ASIC) integrated with a 2-D PZT matrix transducer that enables in-probe digitization with acceptable power dissipation for the next-generation endoscopic and catheter-based 3-D ultrasound imaging systems. To achieve power-efficient massively parallel analog-to-digital conversion (ADC) in a 2-D array, a 10-bit 30 MS/s beamforming ADC that merges the subarray beamforming and digitization functions in the charge domain is proposed. It eliminates the need for costly intermediate buffers, thus significantly reducing both power consumption and silicon area. Self-calibrated charge references are implemented in each subarray to further optimize the system-level power efficiency. High-speed datalinks are employed in combination with the subarray beamforming scheme to realize a 36-fold channel-count reduction and an aggregate output data rate of 6 Gb/s for a prototype receive array of 24 x 6 elements. The ASIC achieves a record power efficiency of 0.91 mW/element during receive. Its functionality has been demonstrated in both electrical and acoustic imaging experiments.

79. A 2D Ultrasound Transducer with Front-End ASIC and Low Cable Count for 3D Forward-Looking Intravascular Imaging: Performance and Characterization
    J. Janjic; M. Tan; E. Noothout; C. Chen; Z. Chan; Z. Y. Chang; R. H. S. H. Beurskens; G. van Soest; A. F. W. van der Steen; M. D. Verweij; M. A. P. Pertijs; N. de Jong;
    IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control,
    Volume 65, Issue 10, pp. 1832--1844, October 2018. Featured Cover Article. DOI: 10.1109/TUFFC.2018.2859824
    
    Abstract: ...

    Intravascular ultrasound is an imaging modality used to visualize atherosclerosis from within the inner lumen of human arteries. Complex lesions like chronic total occlusions require forward-looking intravascular ultrasound (FL-IVUS), instead of the conventional side-looking geometry. Volumetric imaging can be achieved with 2D array transducers, which present major challenges in reducing cable count and device integration. In this work we present an 80-element lead zirconium titanate (PZT) matrix ultrasound transducer for FL-IVUS imaging with a front-end application-specific integrated circuit (ASIC) requiring only 4 cables. After investigating optimal transducer designs we fabricated the matrix transducer consisting of 16 transmit (TX) and 64 receive (RX) elements arranged on top of an ASIC having an outer diameter of 1.5 mm and a central hole of 0.5 mm for a guidewire. We modeled the transducer using finite element analysis and compared the simulation results to the values obtained through acoustic measurements. The TX elements showed uniform behavior with a center frequency of 14 MHz, a -3 dB bandwidth of 44 % and a transmit sensitivity of 0.4 kPa/V at 6 mm. The RX elements showed center frequency and bandwidth similar to the TX elements, with an estimated receive sensitivity of 3.7 μV/Pa. We successfully acquired a 3D FL image of three spherical reflectors in water using delay-and-sum beamforming and the coherence factor method. Full synthetic aperture acquisition can be achieved with frame rates on the order of 100 Hz. The acoustic characterization and the initial imaging results show the potential of the proposed transducer to achieve 3D FL-IVUS imaging.

80. A Phase-Domain Readout Circuit for a CMOS-Compatible Hot-Wire CO2 Sensor
    Z. Cai; R. van Veldhoven; H. Suy; G. de Graaf; K. Makinwa; M. Pertijs;
    IEEE Journal of Solid-State Circuits,
    Volume 53, Issue 11, pp. 3303--3313, November 2018. DOI: 10.1109/JSSC.2018.2866374
    
    Abstract: ...

    This paper presents a readout circuit for a carbon dioxide (CO2) sensor that measures the CO2-dependent thermal time constant of a hot-wire transducer. The readout circuit periodically heats up the transducer and uses a phase-domain modulator to digitize the phase shift of the resulting temperature transients. A single resistive transducer is used both as a heater and as a temperature sensor, thus greatly simplifying its fabrication. To extract the transducer’s resistance, and hence its temperature, in the presence of large heating currents, a pair of transducers is configured as a differentially driven bridge. The transducers and the readout circuit have been implemented in a standard 0.16-μm CMOS technology, with an active area of 0.3 and 3.14 mm2, respectively. The sensor consumes 6.8 mW from a 1.8-V supply, of which 6.3 mW is dissipated in the transducers. A resolution of 94-ppm CO2 is achieved in a 1.8-s measurement time, which corresponds to an energy consumption of 12 mJ per measurement, >10× less than prior CO2 sensors in CMOS technology.

81. CMOS-Compatible Carbon Dioxide Sensors
    Z. Cai; R. van Veldhoven; H. Suy; G. de Graaf; K. A. A. Makinwa; M. Pertijs;
    In Low-Power Analog Techniques, Sensors for Mobile Devices, and Energy Efficient Amplifiers,
    Springer Science \& Business Media, November 2018. DOI: 10.1007/978-3-319-97870-3
    
    Abstract: ...

    This chapter presents two cost-effective sensors that measure ambient carbon dioxide (CO2) concentration, intended for application in smart ventilation systems in buildings or in mobile devices. Both sensors employ a suspended hot-wire transducer to detect the CO2-dependent thermal conductivity (TC) of the ambient air. The resistive transducer is realized in the VIA layer of a standard CMOS process using a single etch step. The first sensor determines the transducer’s CO2-dependent thermal resistance to the surrounding air by measuring its steady-state temperature rise and power dissipation. A ratiometric measurement is realized by employing an identical but capped transducer as a reference. An incremental delta-sigma ADC digitizes the temperature and power ratios of the transducers, from which the ratio of the thermal resistances is calculated. The second sensor is based on a transient measurement of the CO2-dependent thermal time constant of the transducer. The readout circuit periodically heats up the transducer and uses a phase-domain delta-sigma modulator to digitize the CO2-dependent phase shift of the resulting temperature transients. Compared to the ratiometric steady-state measurement, this approach significantly reduces the measurement time and improves the energy efficiency, resulting in a state-of-the art CO2 resolution of 94 ppm at an energy consumption of 12 mJ per measurement.
    
    document

82. A 0.91mW/Element Pitch-Matched Front-End ASIC with Integrated Subarray Beamforming ADC for Miniature 3D Ultrasound Probes
    C. Chen; Z. Chen; D. Bera; E. Noothout; Z. Y. Chang; M. Tan; H. J. Vos; J. G. Bosch; M. D. Verweij; N. de Jong; M. A. P. Pertijs;
    In Dig. Techn. Papers IEEE International Solid-State Circuits Conference (ISSCC),
    pp. 186-187, February 2018. DOI: 10.1109/ISSCC.2018.8310246

83. A 5x5 Microwave Permittivity Sensor Matrix in 0.14-μm CMOS
    Z. Hu; G. Vlachogiannakis; M. A. P. Pertijs; L. C. N. de Vreede; M. Spirito;
    In Proc. IEEE MTT-S International Microwave Symposium (IMS),
    6 2018. DOI: 10.1109/MWSYM.2018.8439438

84. A Phase-Domain Readout Circuit for a CMOS Compatible Thermal-Conductivity-Based Carbon Dioxide Sensor
    Z. Cai; R. van Veldhoven; H. Suy; G. de Graaf; K. A. A. Makinwa; M. A. P. Pertijs;
    In Dig. Techn. Papers IEEE International Solid-State Circuits Conference (ISSCC),
    pp. 332-333, February 2018. DOI: 10.1109/ISSCC.2018.8310319

85. Clamp-on Ultrasonic Flow-metering via Matrix Transducers
    J. Massaad; P. van Neer; D. van Willigen; N. de Jong; M. Pertijs; Martin Verweij;
    In Proc. Int. Conf. on Ultrasonic-based Applications,
    June 2018.

86. Monitoring infant brain perfusion by trans-fontanel echography
    A. J. Kortenbout; H. J. Vos; J. Dudink; M. D. Verweij; M. A. P. Pertijs; J. G. Bosch; N. de Jong;
    In Proc. PhD Training Course Dutch Heart Foundation,
    October 2018.

87. ASIC design for a single-cable 64-element ultrasound probe
    D. van Willigen; J. Janjic; E. Kang; Z. Y. Chang; E. Noothout; M. Verweij; N. de Jong; M. Pertijs;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    IEEE, pp. 1-4, October 2018.
    
    Abstract: ...

    This paper presents an ASIC (Application Specific Integrated Circuit) design for a catheter probe that interfaces 64 piezoelectric elements directly integrated on top of the ASIC to an imaging system using a single micro-coaxial cable. Each of the piezo elements can be used for both transmit (TX) and receive (RX), enabling full synthetic aperture imaging. A prototype has been realized with a 1.5mm diameter circular layout, intended for 3D intra-vascular ultrasound imaging. The functionality of this ASIC has been successfully demonstrated in a 3D imaging experiment. The design allows a single-element transducer to be replaced by a transdcuer array while using the same cable, making it a promising solution for 3D imaging with size constrained probes.

88. A Power-Efficient Transmit Beamformer ASIC for 3-D Catheter-Based/ Endoscopic Probes
    Z. Chen; E. Kang; Z. Y. Chang; E. Noothout; J. G. Bosch; M. Verweij; N. de Jong; M. Pertijs;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    IEEE, October 2018. (abstract).
    
    Abstract: ...

    To reduce cable count in 3D catheter-based or endoscopic probes, generation of the (HV) transmit (TX) signals using an in-probe ASIC is a promising solution. However, such ASICs are subject to stringent power-consumption constraints to limit self-heating. The power consumed by conventional HV pulsers is at least fCV^2, due to the periodic charging/discharging of the transducer element capacitance C. HV switches can be used to connect elements to a pulser in the imaging system, thus only dissipating a fraction of fCV^2 in the probe, but full TX beamforming (BF) cannot be realized using switches. In this work, we propose a power-efficient HV TX circuit capable of providing full TX BF using only 3 HV connections to the system. Implemented in a 0.18um BCD process, the ASIC was fully evaluated by means of post-layout simulations.

89. CMOS-Compatible Carbon Dioxide Sensors
    Z. Cai; R. van Veldhoven; H. Suy; G. de Graaf; K. A. A. Makinwa; M. Pertijs;
    In Proc. Workshop on Advances in Analog Circuit Design (AACD),
    pp. 68-91, April 2018. invited paper. DOI: 10.1007/978-3-319-97870-3
    document

90. A Compact Energy Efficient CMOS Permittivity Sensor Based on Multi-Harmonic Downconversion and Tunable Impedance Bridge
    G. Vlachogiannakis; Z. Hu; H. T. Shivamurthy; A. Neto; M. A. P. Pertijs; L. C. N. de Vreede; M. Spirito;
    In Int. Microwave Biomedical Conference (IMBioC),
    pp. 1--3, June 2018. DOI: 10.1109/IMBIOC.2018.8428950
    
    Abstract: ...

    This paper presents a 0.15×0.3 mm2 complex permittivity sensor integrated in a 40-nm CMOS node. A single-ended patch, employed as a near-field sensing element, is integrated with a double-balanced, fully-differential tunable impedance bridge that is driven by a square RF pulse. The multi-harmonic, intermediate-frequency down-conversion architecture achieves a compact form factor and fast multi-frequency readout. Measurement results show good agreement with theoretical values and the measured relative permittivity variation remains below 0.3 over a 0.1-10 GHz range at a 1-ms measurement time. The energy efficiency resulting from the fast measurement time and the record-small active area allows integration in battery-operated wearables.

91. Feasibility of ultrasound flow measurements via non-linear wave propagation
    J. Massaad; P. L. M. J. van Neer; D. M. van Willigen; N. de Jong; M. A. P. Pertijs; M. D. Verweij;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    IEEE, pp. 1-4, October 2018. DOI: 10.1109/ULTSYM.2018.8579943
    
    Abstract: ...

    Typically, ultrasonic flow meters assume linear wave propagation. Nevertheless, if the transducers of an ultrasonic flow sensor excite a pressure wave with a high amplitude, nonlinear wave propagation effects become significant. The appearance of higher harmonics increases the bandwidth of the received signal, which may potentially lead to a more precise flow measurement. However, the question arises whether the increased bandwidth can be used in practice, since the intensity of the 2nd harmonic can be 25 dB below the fundamental. One exploit of the increased bandwidth is to filter the received signals and to obtain two components: the fundamental and the 2nd harmonic. Differences between the upstream and downstream transit times are directly related to the flow speed, and these can be computed for each component of the received signals. This paper shows that averaging the transit time differences of the fundamental signals and the 2nd harmonic signals results in a lower standard deviation compared to the standard deviation of the transit time differences of the fundamental or the 2nd harmonic signal alone. This demonstrates the feasibility of using non-linear wave propagation to improve the precision of flow measurements using ultrasound.

92. Minimizing the zero-flow error in transit time ultrasonic flow meters
    D. van Willigen; P. van Neer; J. Massaad; N. de Jong; M. Verweij; M. Pertijs;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    IEEE, pp. 1-4, October 2018. DOI: 10.1109/ULTSYM.2018.8579771
    
    Abstract: ...

    Transit-time ultrasonic flow meters are based on the fundamental idea that the flow is the only non-reciprocal effect between an upstream and downstream measurement. Non-identical transducers can be used in a reciprocal manner if the circuit is made reciprocal. In this paper we analyze the effect of driver- and readout electronics on the zero-flow error in transit-time ultrasonic flow meters by simulation and measurement. Using the frequency characteristic of two nonidentical transducers, the cause of the zero-flow error in nonreciprocal circuits is evaluated. Both simulation and measurement results show that the lowest zero-flow error can be obtained by using circuits that have an impedance significantly higher or lower than the impedance of the transducers.

93. A quantitative study on the impact of bit errors on image quality in ultrasound probes with in-probe digitization
    Z. Chen; M. Soozande; H. J. Vos; J. G. Bosch; M. Verweij; N. de Jong; M. Pertijs;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    IEEE, October 2018. (abstract).
    
    Abstract: ...

    Integrating ultrasound transducers with ASICs which digitize and multiplex the received echo signals effectively mitigates the burden of signal transmission for 3-D catheter-based or endoscopic probes. Multiplexing the echo signals from multiple elements onto a cable reduces the cable count, but requires a higher data rate per cable, which typically involves a trade-off between power consumption and bit-error rate (BER). Understanding the impact of finite BER on the resulting image quality is a necessity to optimize the cable count and power consumption. In this work, this impact is quantitatively assessed using Matlab simulations. The effectiveness of error correction is also investigated.

94. Virtually Extended Array imaging improves lateral resolution in high frame rate volumetric imaging
    M. Soozande; F. Fool; M. Shabanimotlagh; M. Pertijs; M. Verweij; H. J. Vos; J. G. Bosch; N. de Jong;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    IEEE, pp. 1-4, October 2018. DOI: 10.1109/ULTSYM.2018.8580018
    
    Abstract: ...

    Matrix arrays for endoscopic and catheter-based applications are restricted to small physical apertures, which limits their lateral resolution. In addition, when aiming for high volume rate imaging and utilizing the recent methods of transmitting a single or few diverging waves (DW), lateral resolution further deteriorates. In this work, we propose a high frame rate transmission scheme which outperforms alternative methods in lateral resolution. To improve the lateral resolution and side-lobe level, we propose to transmit only on a sub-aperture on either side of the array and apply a specific weighting function to received data. Compared to single-DW imaging, the proposed Sub-aperture Virtually Extended Array reduces the PSF width and sidelobe level by 16% and 5dB respectively and provides a similar SNR at the cost of halving the frame rate.

95. A Phase-Domain Readout Circuit for a CMOS Compatible Thermal-Conductivity-Based Carbon Dioxide Sensor
    Z. Cai; R. van Veldhoven; H. Suy; G. de Graaf; K. A. A. Makinwa; M. A. P. Pertijs;
    In Dig. Techn. Papers IEEE International Solid-State Circuits Conference (ISSCC),
    pp. 332-333, February 2018. DOI: 10.1109/ISSCC.2018.8310319

96. Data collection system, in particular suitable for imaging of a distant object
    D. M. van Willigen; M. A. P. Pertijs;
    Patent, Dutch NL2020426B1, February 2018.

97. A 7μW Offset-and Temperature-Compensated pH-to-Digital Converter
    S. H. Shalmany; M. Merz; A. Fekri; Z. Y. Chang; R. J. O. M. Hoofman; M. A. P. Pertijs;
    Journal of Sensors,
    Volume 2017, Issue 6158689, January 2017. DOI: 10.1155/2017/6158689
    
    Abstract: ...

    This paper demonstrates a micropower offset- and temperature-compensated smart pH sensor, intended for use in battery-powered RFID systems that monitor the quality of perishable products. Low operation power is essential in such systems to enable autonomous logging of environmental parameters, such as the pH level, over extended periods of time using only a small, low-cost battery. The pH-sensing element in this work is an ion-sensitive extended-gate field-effect transistor (EGFET), which is incorporated in a low-power sensor front-end. The front-end outputs a pH-dependent voltage, which is then digitized by means of a co-integrated incremental delta-sigma ADC. To compensate for the offset and temperature cross-sensitivity of the EGFET, a compensation scheme using a calibration process and a temperature sensor has been devised. A prototype chip has been realized in a 0.16 μm CMOS process. It occupies 0.35 × 3.9 mm2 of die area and draws only 4 μA from a 1.8 V supply. Two different types of custom packaging have been used for measurement purposes. The pH sensor achieves a linearity of better than ±0.1 for pH values ranging from 4 to 10. The calibration and compensation scheme reduces errors due to temperature cross-sensitivity to less than ±0.1 in the temperature range of 6°C to 25°C.

98. A Front-end ASIC with Receive Sub-Array Beamforming Integrated with a 32 × 32 PZT Matrix Transducer for 3-D Transesophageal Echocardiography
    C. Chen; Z. Chen; D. Bera; S. B. Raghunathan; M. Shabanimotlagh; E. Noothout; Z. Y. Chang; J. Ponte; C. Prins; H. J. Vos; J. G. Bosch; M. D. Verweij; N. de Jong; M. A. P. Pertijs;
    IEEE Journal of Solid-State Circuits,
    Volume 52, Issue 4, pp. 994‒1006, April 2017. DOI: 10.1109/JSSC.2016.2638433
    
    Abstract: ...

    This paper presents a power- and area-efficient front-end application-specific integrated circuit (ASIC) that is directly integrated with an array of 32 × 32 piezoelectric transducer elements to enable next-generation miniature ultrasound probes for real-time 3-D transesophageal echocardiography. The 6.1 × 6.1 mm2 ASIC, implemented in a low-voltage 0.18-μm CMOS process, effectively reduces the number of receive (RX) cables required in the probe's narrow shaft by ninefold with the aid of 96 delay-and-sum beamformers, each of which locally combines the signals received by a sub-array of 3 × 3 elements. These beamformers are based on pipeline-operated analog sample-and-hold stages and employ a mismatch-scrambling technique to prevent the ripple signal associated with the mismatch between these stages from limiting the dynamic range. In addition, an ultralow-power low-noise amplifier architecture is proposed to increase the power efficiency of the RX circuitry. The ASIC has a compact element matched layout and consumes only 0.27 mW/channel while receiving, which is lower than the state-of-the-art circuit. Its functionality has been successfully demonstrated in 3-D imaging experiments.

99. A Precision Capacitance-to-Digital Converter with 16.7-bit ENOB and 7.5 ppm/°C Thermal Drift
    R. Yang; M. A. P. Pertijs; S. Nihtianov;
    IEEE Journal of Solid-State Circuits,
    Volume 52, Issue 11, pp. 3018-3031, November 2017. DOI: 10.1109/jssc.2017.2734900
    
    Abstract: ...

    This paper presents a high-precision capacitance-to-digital converter (CDC) for displacement measurement in advanced industrial applications, based on a charge-balancing third-order delta–sigma modulator. To achieve high precision, this CDC employs a precision external resistive reference and a quartz-oscillator-based time reference instead of a reference capacitor. To minimize the error contribution of the CDC circuitry, various precision circuit techniques, such as chopping and auto-zeroing, are applied at both system and circuit level. Measurement results of the prototype realized in 0.35-μm CMOS technology show that the CDC achieves an rms resolution of 42 aF across a capacitance range from 6 to 22 pF, corresponding to an effective number of bits (ENOB) of 16.7 bit. The conversion time for one measurement is 10.5 ms, during which the CDC consumes 230 μA from a 3.3-V single supply. The measured thermal stability is within ±7.5 ppm/°C across a temperature range from 20 °C to 70 °C, which represents a significant improvement compared to the state of the art. After a two-point calibration, all ten measured samples from one batch show absolute accuracy below ±25 fF across the entire capacitance measurement range.

100. A CMOS Readout Circuit for Resistive Transducers Based on Algorithmic Resistance and Power Measurement
     Z. Cai; L. Rueda Guerrero; A. Louwerse; H. Suy; R. van Veldhoven; K. Makinwa; M. Pertijs;
     IEEE Sensors Journal,
     Volume 17, Issue 23, pp. 7917-7927, December 2017. DOI: 10.1109/JSEN.2017.2764161
     
     Abstract: ...

     This paper reports a readout circuit capable of accurately measuring not only the resistance of a resistive transducer, but also the power dissipated in it, which is a critical parameter in thermal flow sensors or thermal-conductivity sensors. A front-end circuit, integrated in a standard CMOS technology, sets the voltage drop across the transducer, and senses the resulting current via an on-chip reference resistor. The voltages across the transducer and the reference resistor are digitized by a time-multiplexed high-resolution analog-todigital converter (ADC) and post-processed to calculate resistance and power dissipation. To obtain accurate resistance and power readings, a voltage reference and a temperature-compensated reference resistor are required. An accurate voltage reference is constructed algorithmically, without relying on precision analog signal processing, by using the ADC to successively digitize the base–emitter voltages of an on-chip bipolar transistor biased at several different current levels, and then combining the results to obtain the equivalent of a precision curvature-corrected bandgap reference with a temperature coefficient of 18 ppm/°C, which is close to the state-of-the-art. We show that the same ADC readings can be used to determine die temperature, with an absolute inaccuracy of ±0.25 °C (5 samples, min–max) after a 1-point trim. This information is used to compensate for the temperature dependence of the on-chip polysilicon reference resistor, effectively providing a temperature-compensated resistance reference. With this approach, the resistance and power dissipation of a 100 transducer have been measured with an inaccuracy of less than ±0.55 and ±0.8\%, respectively, from −40 °C to 125 °C.

101. A CMOS Readout Circuit for Resistive Transducers Based on Algorithmic Resistance and Power Measurement
     Z. Cai; L. Rueda Guerrero; A. Louwerse; H. Suy; R. van Veldhoven; K. Makinwa; M. Pertijs;
     IEEE Sensors Journal,
     Volume 17, Issue 23, pp. 7917-7927, December 2017. DOI: 10.1109/JSEN.2017.2764161
     
     Abstract: ...

     This paper reports a readout circuit capable of accurately measuring not only the resistance of a resistive transducer, but also the power dissipated in it, which is a critical parameter in thermal flow sensors or thermal-conductivity sensors. A front-end circuit, integrated in a standard CMOS technology, sets the voltage drop across the transducer, and senses the resulting current via an on-chip reference resistor. The voltages across the transducer and the reference resistor are digitized by a time-multiplexed high-resolution analog-todigital converter (ADC) and post-processed to calculate resistance and power dissipation. To obtain accurate resistance and power readings, a voltage reference and a temperature-compensated reference resistor are required. An accurate voltage reference is constructed algorithmically, without relying on precision analog signal processing, by using the ADC to successively digitize the base–emitter voltages of an on-chip bipolar transistor biased at several different current levels, and then combining the results to obtain the equivalent of a precision curvature-corrected bandgap reference with a temperature coefficient of 18 ppm/°C, which is close to the state-of-the-art. We show that the same ADC readings can be used to determine die temperature, with an absolute inaccuracy of ±0.25 °C (5 samples, min–max) after a 1-point trim. This information is used to compensate for the temperature dependence of the on-chip polysilicon reference resistor, effectively providing a temperature-compensated resistance reference. With this approach, the resistance and power dissipation of a 100 transducer have been measured with an inaccuracy of less than ±0.55 and ±0.8\%, respectively, from −40 °C to 125 °C.

102. Acoustic Characterization of a 32 × 32 Element PZT-on-ASIC Matrix Transducer for 3D Transesophageal Echocardiography
     M. Shabanimotlagh; S. Raghunathan; D. Bera; Z. Chen; C. Chen; V. Daeichin; M. Pertijs; J. G. Bosch; N. de Jong; M. Verweij;
     In Dutch Bio-Medical Engineering Conference,
     The Netherlands, 2017.

103. A Fresnel-inspired approach for steering and focusing a pulsed transmit beam with matrix array transducers
     M. Verweij; M. Pertijs; J. de Wit; F. Fool; H. Vos; N. de Jong;
     In The Journal of the Acoustical Society of America,
     June 2017. DOI: 10.1121/1.4987739
     
     Abstract: ...

     Matrix ultrasound transducers for medical diagnostic purposes are commercially available for a decade. A typical matrix transducer contains 1000 + elements, with a trend towards more and smaller elements. This number renders direct connection of each individual element to an ultrasound machine impractical. Consequently, it is cumbersome to employ traditional focusing and beamforming approaches that are based on transmit and receive signals having an individual time delay for each element. To reduce cable count during receive, one approach is to apply sub-arrays that locally combine the element signals using programmable delay-and-sum hardware, resulting in reduction by a factor 10. In transmit, achieving cable count reduction while keeping focusing and steering capabilities turns problematic once it becomes impossible to locally equip each element with its own high voltage pulser. To overcome this bottleneck for decreasing element size, here we present a Fresnel-inspired hardware and beam forming approach that is based on transmit pulses consisting of several periods of an oscillating waveform. These will be derived from one oscillating high voltage signal by using local switching and timing hardware. To demonstrate the feasibilities of our approach, we will show beam profiles and images for a miniature matrix transducer that we are currently developing.

104. A Front-End ASIC with High-Voltage Transmit Switching and Receive Digitization for Forward-Looking Intravascular Ultrasound
     M. Tan; C. Chen; Z. Chen; J. Janjic; V. Daeichin; Z. Y. Chang; E. Noothout; G. van Soest; M. Verweij; N. de Jong; M. Pertijs;
     In Proc. IEEE Custom Integrated Circuits Conference (CICC),
     IEEE, pp. 1‒4, April 2017. DOI: 10.1109/cicc.2017.7993708

105. An Element-Matched Band-Pass Delta-Sigma ADC for Ultrasound Imaging
     M. D’Urbino; C. Chen; Z. Chen; Z. Y. Chang; J. Ponte; B. Lippe; M. Pertijs;
     In Proc. IEEE Asian Solid State Circuits Conference (A-SSCC),
     IEEE, pp. 137-140, November 2017. winner Student Design Contest. DOI: 10.1109/ASSCC.2017.8240235

106. A Reconfigurable 24 × 40 Element Transceiver ASIC for Compact 3D Medical Ultrasound Probes
     E. Kang; Q. Ding; M. Shabanimotlagh; P. Kruizinga; Z. Y. Chang; E. Noothout; H. J. Vos; J. G. Bosch; M. D. Verweij; N. de Jong; M. A. P. Pertijs;
     In Proc. European Solid-State Circuits Conference (ESSCIRC),
     IEEE, pp. 211-214, September 2017.

107. A compact sensor readout circuit with temperature, capacitance and voltage sensing functionalities
     B. Yousefzadeh; W. Wu; B. Buter; K. Makinwa; M. Pertijs;
     In NXP Low-Power Design Conference,
     NXP, June 2017.
     
     Abstract: ...

     This paper presents an area- and energy-efficient sensor readout circuit, which can precisely digitize temperature, capacitance and voltage. The three modes use only on-chip references and employ a shared zoom ADC based on SAR and ΔΣ conversion to save die area. Measurements on 24 samples from a single wafer show a temperature inaccuracy of ±0.2 °C (3σ) over the military temperature range (-55°C to 125°C). The voltage sensing shows an inaccuracy of ±0.5\%. The sensor also offers 18.7-ENOB capacitance-to-digital conversion, which handles up to 3.8 pF capacitance with a 0.76 pJ/conv.-step energy-efficiency FoM. It occupies 0.33 mm² in a 0.16 μm CMOS process and draws 4.6 μA current from a 1.8 V supply.

108. A Compact Sensor Readout Circuit with Combined Temperature, Capacitance and Voltage Sensing Functionality
     B. Yousefzadeh; W. Wu; B. Buter; K. A. A. Makinwa; M. Pertijs;
     In Dig. Techn. Paper IEEE Symposium on VLSI Circuits (VLSI),
     IEEE, pp. 1‒2, June 2017. DOI: 10.23919/VLSIC.2017.8008555
     
     Abstract: ...

     This paper presents an area- and energy-efficient sensor readout circuit, which can precisely digitize temperature, capacitance and voltage. The three modes use only on-chip references and employ a shared zoom ADC based on SAR and ΔΣ conversion to save die area. Measurements on 24 samples from a single wafer show a temperature inaccuracy of ±0.2 °C (3σ) over the military temperature range (-55°C to 125°C). The voltage sensing shows an inaccuracy of ±0.5\%. The sensor also offers 18.7-ENOB capacitance-to-digital conversion, which handles up to 3.8 pF capacitance with a 0.76 pJ/conv.-step energy-efficiency FoM. It occupies 0.33 mm² in a 0.16 μm CMOS process and draws 4.6 μA current from a 1.8 V supply.

109. A Front-End ASIC for Miniature 3-D Ultrasound Probes with In-Probe Receive Digitization
     C. Chen; Z. Chen; D. Bera; E. Noothout; Z. Y. Chang; H. Vos; J. Bosch; M. Verweij; N. de Jong; M. Pertijs;
     In Proc. IEEE International Ultrasonics Symposium (IUS),
     IEEE, pp. 1-4, September 2017. Winner Best Student Paper Competition. DOI: 10.1109/ULTSYM.2017.8091913
     
     Abstract: ...

     This paper presents a front-end application-specific integrated circuit (ASIC) that demonstrates the feasibility of inprobe digitization for next-generation miniature 3-D ultrasound probes with acceptable power- and area-efficiency. The proposed design employs a low-power charge-domain ADC that is directly merged with the sample-and-hold delay lines in each subarray, and high-speed datalinks at the ASIC periphery to realize an additional channel-count reduction compared to prior work based on analog subarray beamforming. The 4.8 × 2 mm 2 ASIC, which has a compact layout element-matched to a 5-MHz 150-μm-pitch PZT matrix transducer, achieves an overall 36-fold channel-count reduction and a state-of-the-art power-efficiency with less than 1 mW/element power dissipation while receiving, which is acceptable even when scaled up to a 1000-element probe. The prototype ASIC has been fabricated in a 0.18 μm CMOS process. Its functionality has been successfully evaluated with both electrical and acoustical measurements.

110. Forward-Looking IVUS Transducer with Front-End ASIC for 3D Imaging
     J. Janjic; M. Tan; C. Chen; Z. Chen; E. Noothout; Z. Y. Chang; G. van Soest; M. Verweij; A. F. W. van der Steen; M. Pertijs; N. de Jong;
     In Proc. IEEE International Ultrasonics Symposium (IUS),
     IEEE, pp. 1-1, September 2017. (abstract).
     
     Abstract: ...

     Forward-looking intravascular ultrasound (FL-IVUS) transducers are needed to image complex lesions in the coronary arteries, such as chronic total occlusions (CTOs). To achieve 2D and 3D FL-IVUS imaging, transducer arrays can be integrated at the tip of the catheter. However, connecting the elements is challenging due to the limited space available. In this work, we present a FL-IVUS matrix transducer consisting of 16 transmit and 64 receive elements, which are interfaced with an ASIC that requires only 4 micro-coaxial cables. The transducer performance was characterized by hydrophone measurements and FL imaging of three spherical reflectors.

111. Volumetric imaging using adult matrix TEE with separated transmit and receive array
     D. Bera; F. van den Adel; N. Radeljic-Jakic; B. Lippe; M. Soozande; M. Pertijs; M. Verweij; P. Kruizinga; V. Daeichin; H. Vos; J. Bosch; N. de Jong;
     In Proc. IEEE International Ultrasonics Symposium (IUS),
     IEEE, pp. 1-1, September 2017. (abstract). DOI: 10.1109/ULTSYM.2017.8092906
     
     Abstract: ...

     The design of 3D TEE transducers poses severe technical challenges: channel count, electronics integration with high and low voltages, heat dissipation, etc. We present an adult matrix TEE probe with separate transmit (Tx) and receive (Rx) arrays allowing optimization in both Tx and Rx [1]. Tx elements are directly wired out, Rx employs integrated micro-beamformers in low-voltage (1.8/5.0V) chip technology. The prototype is fully integrated into a gastroscopic tube.

112. Towards 3D ultrasound imaging of the carotid artery using a programmable and tileable matrix array
     P. Kruizinga; E. Kang; M. Shabanimotlagh; Q. Ding; E. Noothout; Z. Y. Chang; H. J. Vos; J. G. Bosch; M. D. Verweij; M. A. P. Pertijs; N. de Jong;
     In Proc. IEEE International Ultrasonics Symposium (IUS),
     IEEE, pp. 1-3, September 2017. DOI: 10.1109/ULTSYM.2017.8091570
     
     Abstract: ...

     Accurate assessment of carotid artery disease by measuring blood flow, plaque deformation and pulse wave velocity using ultrasound imaging requires 3D information. Additionally, the volume rates should be high enough (> 1 kHz) to capture the full range of these fast transient phenomena. For this purpose, we have built a programmable, tileable matrix array that is capable of providing 3D ultrasound imaging at such volume rates. This array contains an application-specific integrated circuit (ASIC) right beneath the acoustic piezo-stack. The ASIC enables fast programmable switching between various configurations of elements connected to the acquisition system via a number of channels far smaller than the number of transducer elements. This design also allows for expanding the footprint by tiling several of these arrays together into one large array. We explain the working principles and show the first basic imaging results of a 2-by-1 tiled array.

113. Optimizing the directivity of piezoelectric matrix transducer elements mounted on an ASIC
     M. Shabanimotlagh; S. Raghunathan; V. Daeichin; P. Kruizinga; H. J. Vos; M. A. P. Pertijs; J. G. Bosch; N. de Jong; M. D. Verweij;
     In Proc. IEEE International Ultrasonics Symposium (IUS),
     IEEE, pp. 1-4, September 2017. DOI: 10.1109/ULTSYM.2017.8091752
     
     Abstract: ...

     Over the last decade, clinical studies show a strong interest in real-time 3D imaging. This calls for ultrasound probes with high-element-count 2D matrix transducer arrays. These may be interfaced to an imaging system using an in-probe Application Specific Integrated Circuit (ASIC) that takes care of signal amplification, element switching, sub-array beamforming, etc. Since the ASIC is made from silicon and is mounted directly behind the transducer elements, it can acoustically be regarded as a rigid plate that can sustain traveling lateral waves. These waves lead to acoustical cross-talk between the elements, and results in extra peaks in the directivity pattern. We propose two solutions to this problem, based on numerical simulations. One approach is to decrease the phase velocity in the silicon by reducing the silicon thickness and absorbing the energy using a proper backing material. Another solution is to disturb the waves inside the silicon plate by sub-dicing the back-side of the ASIC. We conclude that both solutions can be used to improve the directivity pattern.

114. A Compact Sensor Readout Circuit with Combined Temperature, Capacitance and Voltage Sensing Functionality
     B. Yousefzadeh; W. Wu; B. Buter; K. A. A. Makinwa; M. Pertijs;
     In Dig. Techn. Paper IEEE Symposium on VLSI Circuits (VLSI),
     IEEE, pp. 1‒2, June 2017. DOI: 10.23919/VLSIC.2017.8008555
     
     Abstract: ...

     This paper presents an area- and energy-efficient sensor readout circuit, which can precisely digitize temperature, capacitance and voltage. The three modes use only on-chip references and employ a shared zoom ADC based on SAR and ΔΣ conversion to save die area. Measurements on 24 samples from a single wafer show a temperature inaccuracy of ±0.2 °C (3σ) over the military temperature range (-55°C to 125°C). The voltage sensing shows an inaccuracy of ±0.5\%. The sensor also offers 18.7-ENOB capacitance-to-digital conversion, which handles up to 3.8 pF capacitance with a 0.76 pJ/conv.-step energy-efficiency FoM. It occupies 0.33 mm² in a 0.16 μm CMOS process and draws 4.6 μA current from a 1.8 V supply.

115. Ratiometric device
     Z. Cai; M. A. P. Pertijs; R. H. M. van Veldhoven; K. A. A. Makinwa;
     Patent, United States 9,835,575B2, December 2017.

116. A Broadband Polyvinylidene Difluoride-Based Hydrophone with Integrated Readout Circuit for Intravascular Photoacoustic Imaging
     V. Daeichin; C. Chen; Q. Ding; M. Wu; R. Beurskens; G. Springeling; E. Noothout; M. D. Verweij; K. W. A. van Dongen; J. G. Bosch; A. F. W. van der Steen; N. de Jong; M. Pertijs; G. van Soest;
     Ultrasound in Medicine \& Biology,
     Volume 42, Issue 5, pp. 1239‒1243, May 2016. DOI: 10.1016/j.ultrasmedbio.2015.12.016
     
     Abstract: ...

     Intravascular photoacoustic (IVPA) imaging can visualize the coronary atherosclerotic plaque composition on the basis of the optical absorption contrast. Most of the photoacoustic (PA) energy of human coronary plaque lipids was found to lie in the frequency band between 2 and 15 MHz requiring a very broadband transducer, especially if a combination with intravascular ultrasound is desired. We have developed a broadband polyvinylidene difluoride (PVDF) transducer (0.6 × 0.6 mm, 52 μm thick) with integrated electronics to match the low capacitance of such a small polyvinylidene difluoride element (<5 pF/mm2) with the high capacitive load of the long cable (∼100 pF/m). The new readout circuit provides an output voltage with a sensitivity of about 3.8 μV/Pa at 2.25 MHz. Its response is flat within 10 dB in the range 2 to 15 MHz. The root mean square (rms) output noise level is 259 μV over the entire bandwidth (1–20 MHz), resulting in a minimum detectable pressure of 30 Pa at 2.25 MHz.

117. A Prototype PZT Matrix Transducer with Low-Power Integrated Receive ASIC for 3D Transesophageal Echocardiography.
     C. Chen; S. Raghunathan; Z. Yu; M. Shabanimotlag; Z. Chen; Z. Y. Chang; S. Blaak; C. Prins; J. Ponte; E. Noothout; H. J. Vos; J. G. Bosch; M. D. Verweij; N. de Jong; M. A. P. Pertijs;
     IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control,
     Volume 63, Issue 1, pp. 47‒59, January 2016. DOI: 10.1109/tuffc.2015.2496580
     
     Abstract: ...

     This paper presents the design, fabrication, and experimental evaluation of a prototype lead zirconium titanate (PZT) matrix transducer with an integrated receive ASIC, as a proof of concept for a miniature three-dimensional (3-D) transesophageal echocardiography (TEE) probe. It consists of an array of 9 × 12 piezoelectric elements mounted on the ASIC via an integration scheme that involves direct electrical connections between a bond-pad array on the ASIC and the transducer elements. The ASIC addresses the critical challenge of reducing cable count, and includes front-end amplifiers with adjustable gains and microbeamformer circuits that locally process and combine echo signals received by the elements of each 3 × 3 subarray. Thus, an order-of-magnitude reduction in the number of receive channels is achieved. Dedicated circuit techniques are employed to meet the strict space and power constraints of TEE probes. The ASIC has been fabricated in a standard 0.18-μm CMOS process and consumes only 0.44 mW/channel. The prototype has been acoustically characterized in a water tank. The ASIC allows the array to be presteered across ±37° while achieving an overall dynamic range of 77 dB. Both the measured characteristics of the individual transducer elements and the performance of the ASIC are in good agreement with expectations, demonstrating the effectiveness of the proposed techniques.

118. A 30-ppm <80 nJ Ring-Down-Based Readout Circuit for Resonant Sensors
     H. Jiang; Z. Y. Chang; M. A. P. Pertijs;
     IEEE Journal of Solid-State Circuits,
     Volume 51, Issue 1, pp. 187‒195, January 2016. DOI: 10.1109/JSSC.2015.2470552
     
     Abstract: ...

     This paper presents an energy-efficient readout circuit for micro-machined resonant sensors. It operates by briefly exciting the sensor at a frequency close to its resonance frequency, after which resonance frequency and quality factor are determined from a single ring-down transient. The circuit employs an inverter-based trans-impedance amplifier to sense the ring-down current, with a programmable feedback network to enable the readout of different resonant sensors. An inverter-based comparator with dynamically-adjusted threshold levels tracks the ring-down envelope to measure quality factor, and detects zero crossings to measure resonance frequency. The excitation frequency is dynamically adjusted to accommodate large resonance frequency shifts. Experimental results obtained with a prototype fabricated in 0.35 μm standard CMOS technology and three different SiN resonators are in good agreement with conventional impedance analysis. The prototype achieves a frequency resolution better than 30 ppm while consuming less than 80 nJ/meas from a 1.8 V supply, which is 7.8x less than the state-of-the-art.

119. A Ratiometric Readout Circuit for Thermal-Conductivity-Based Resistive CO$_2$ Sensors
     Z. Cai; R. H. M. van Veldhoven; A. Falepin; H. Suy; E. Sterckx; C. Bitterlich; K. A. A. Makinwa; M. A. P. Pertijs;
     IEEE Journal of Solid-State Circuits,
     Volume 51, Issue 10, pp. 2453‒2474, October 2016. DOI: 10.1109/jssc.2016.2587861
     
     Abstract: ...

     This paper reports a readout circuit for a resistive CO2 sensor, which operates by measuring the CO2-dependent thermal conductivity of air. A suspended hot-wire transducer, which acts both as a resistive heater and temperature sensor, exhibits a CO2-dependent heat loss to the surrounding air, allowing CO2 concentration to be derived from its temperature rise and power dissipation. The circuit employs a dual-mode incremental delta-sigma ADC to digitize these parameters relative to those of an identical, but isolated, reference transducer. This ratiometric approach results in a measurement that does not require precision voltage or power references. The readout circuit uses dynamically-swapped transducer pairs to cancel their baseline-resistance, so as to relax the required dynamic range of the ADC. In addition, dynamic element matching (DEM) is used to bias the transducer pairs at an accurate current ratio, making the measurement insensitive to the precise value of the bias current. The readout circuit has been implemented in a standard 0.16 μm CMOS technology. With commercial resistive micro-heaters, a CO2 sensing resolution of about 200 ppm (1σ) was achieved in a measurement time of 30 s. Similar results were obtained with CMOS-compatible tungsten-wire transducers, paving the way for fully-integrated CO2 sensors for air-quality monitoring.

120. An Integrated Carbon Dioxide Sensor for Air-Quality Monitoring
     Z. Cai; R. H. M. van Veldhoven; A. Falepin; H. Suy; E. Sterckx; C. Bitterlich; K. A. A. Makinwa; M. A. P. Pertijs;
     In Proc. Conference for ICT-Research in the Netherlands (ICT.OPEN),
     The Netherlands, March 2016.

121. Acoustic Characterisation of a 32 × 32 Element PZT-on-CMOS Matrix Transducer for 3D TEE
     S. Raghunathan; D. Bera; C. Chen; Z. Chen; M. Shabanimotlagh; E. Noothout; Z. Y. Chang; H. Vos; C. Prins; J. Ponte; J. Bosch; M. Pertijs; N. de Jong; M. Verweij;
     In Proc. IEEE International Ultrasonics Symposium (IUS),
     September 2016. (abstract).

122. A front-end ASIC with receive sub-array beamforming integrated with a 32 × 32 PZT matrix transducer for 3-D transesophageal echocardiography
     C. Chen; Z. Chen; D. Bera; S. B. Raghunathan; M. Shabanimotlagh; E. Noothout; Z. Y. Chang; J. Ponte; C. Prins; H. J. Vos; J. G. Bosch; M. D. Verweij; N. de Jong; M. A. P. Pertijs;
     In Dig. Techn. Paper IEEE Symposium on VLSI Circuits (VLSI),
     IEEE, pp. 1‒2, September 2016. DOI: 10.1109/vlsic.2016.7573470

123. A 40-nm CMOS permittivity sensor for chemical/biological material characterization at RF/microwave frequencies
     G. Vlachogiannakis; M. Spirito; M. A. P. Pertijs; L. C. N. de Vreede;
     In Proc. IEEE MTT-S International Microwave Symposium (IMS),
     IEEE, pp. 1‒4, May 2016. DOI: 10.1109/mwsym.2016.7540260

124. A broadband PVDF-based hydrophone with integrated readout circuit for intravascular photoacoustic imaging
     V. Daeichin; C. Chen; Q. Ding; M. Wu; R. Beurskens; G. Springeling; E. Noothout; M. D. Verweij; K. W.A. van Dongen; J. G. Bosch; A. F. W. van der Steen; N. de Jong; M. Pertijs; G. van Soest;
     In Proc. SPIE Photonics West,
     SPIE, February 2016. DOI: 10.1016/j.ultrasmedbio.2015.12.016
     
     Abstract: ...

     Intravascular photoacoustic (IVPA) imaging can visualize the coronary atherosclerotic plaque composition on the basis of the optical absorption contrast. Most of the photoacoustic (PA) energy of human coronary plaque lipids was found to lie in the frequency band between 2 and 15 MHz requiring a very broadband transducer, especially if a combination with intravascular ultrasound is desired. We have developed a broadband polyvinylidene difluoride (PVDF) transducer (0.6 × 0.6 mm, 52 μm thick) with integrated electronics to match the low capacitance of such a small polyvinylidene difluoride element (<5 pF/mm2) with the high capacitive load of the long cable (∼100 pF/m). The new readout circuit provides an output voltage with a sensitivity of about 3.8 μV/Pa at 2.25 MHz. Its response is flat within 10 dB in the range 2 to 15 MHz. The root mean square (rms) output noise level is 259 μV over the entire bandwidth (1–20 MHz), resulting in a minimum detectable pressure of 30 Pa at 2.25 MHz.

125. The role of sub-dicing in the acoustical design of an ultrasound matrix transducer for carotid arteries imaging
     M. Shabanimotlagh; J. Janjic; S. Raghunathan; M. A. P. Pertijs; N. de Jong; M. Verweij;
     In Proc. IEEE International Ultrasonics Symposium (IUS),
     IEEE, pp. 1‒4, September 2016. DOI: 10.1109/ultsym.2016.7728470
     
     Abstract: ...

     Accurate diagnostics of stenosis and blood flow distribution in carotid arteries requires transducers capable of producing 3D volume images with high frame rate for real time imaging. In the process of designing a matrix probe, an important goal is to realize the acoustic stack with high sensitivity and bandwidth. In this study, we employ a finite element analysis to evaluate the effect of sub-dicing on the performance of an acoustic stack in a piezoelectric matrix array. The array is integrated with an Application Specific Integrated Circuit (ASIC), which performs the task of signal amplification and efficient data reduction. The results show that two sub-dicing cuts can improve the sensitivity by 40%, bandwidth by 20%, and reduce the ringing time by 43%, which are all desired for improving the image quality.

126. Three-dimensional beamforming combining micro-beamformed RF datasets
     D. Bera; H. J. Vos; S. B. Raghunathan; C. Chen; Z. Chen; M. D. Verweij; M. A. P. Pertijs; N. de Jong; J. G. Bosch;
     In Proc. IEEE International Ultrasonics Symposium (IUS),
     IEEE, pp. 1‒4, September 2016. DOI: 10.1109/ultsym.2016.7728449
     
     Abstract: ...

     A general challenge in 3D volumetric imaging is the large channel count. One solution uses integrated microbeamformers. The reconstruction of the entire volume from these micro-beamformed datasets can be performed in many ways. In this paper we propose two 3D multiline beamforming techniques, suitable for producing volumes at high frame rate and compare the image qualities to a fully-sampled matrix. The performance of the proposed beamforming techniques was evaluated with simulations in FieldII. Results show that the proposed simple volume reconstruction technique (using 25 transmissions) produces volumes at very high frame rate, but with sharp intensity changes within the volume. The proposed advanced technique (using 169 transmissions) produces volumes very similar to a fully-sampled matrix transducer despite the micro-beamforming.

127. A ratiometric readout circuit for thermal-conductivity-based resistive gas sensors
     Z. Cai; R. H. M. van Veldhoven; A. Falepin; H. Suy; E. Sterckx; K. A. A. Makinwa; M. A. P. Pertijs;
     In Proc. European Solid-State Circuits Conference (ESSCIRC),
     IEEE, pp. 275‒278, September 2015. DOI: 10.1109/esscirc.2015.7313880

128. Acoustic Characterisation of a PZT Matrix With Integrated Electronics for a 3D-TEE Probe
     S. Raghunathan; C. Chen; M. Shabanimotlagh; Z. Chen; S. Blaak; Z. Yu; C. Prins; M. Pertijs; J. Bosch; N. de Jong; M. Verweij;
     In Proc. IEEE International Ultrasonics Symposium (IUS),
     October 2015. (abstract).

129. Low Power Receive Electronics for a Miniature Real-Time 3D Ultrasound Probe
     Z. Chen; C. Chen; S. B. Raghunathan; D. Bera; Z. Chang; S. Blaak; C. Prins; J. Ponte; J. G. Bosch; N. de Jong; M. D. Verweij; M. A. P. Pertijs;
     In Proc. Conference for ICT-Research in the Netherlands (ICT.OPEN),
     The Netherlands, March 2015.

130. A compact 0.135-mW/channel LNA array for piezoelectric ultrasound transducers
     C. Chen; Z. Chen; Z. Y. Chang; M. A. P. Pertijs;
     In Proc. European Solid-State Circuits Conference (ESSCIRC),
     IEEE, pp. 404‒407, September 2015. DOI: 10.1109/esscirc.2015.7313913

131. An integrated carbon dioxide sensor based on ratiometric thermal-conductivity measurement
     Z. Cai; van R. H. M. Veldhoven; A. Falepin; H. Suy; E. Sterckx; K. A. A. Makinwa; M. A. P. Pertijs;
     In Proc. International Conference on Solid-State Sensors, Actuators and Microsystems (TRANSDUCERS),
     IEEE, pp. 622‒625, June 2015. DOI: 10.1109/transducers.2015.7181000

132. Low-power receive electronics for a miniature real-time 3D ultrasound probe
     M. Pertijs; C. Chen; S. Raghunathan; Z. Yu; M. ShabaniMotlagh; Z. Chen; Z. Y. Chang; E. Noothout; S. Blaak; J. Ponte; C. Prins; H. Bosch; M. Verweij; N. de Jong;
     In Proc. IEEE International Workshop on Advances in Sensors and Interfaces (IWASI),
     IEEE, pp. 235‒238, June 2015. invited paper. DOI: 10.1109/iwasi.2015.7184963

133. A generic read-out circuit for resistive transducers
     B. Yousefzadeh; U. Sonmez; N. Mehta; J. Borremans; M. A. P. Pertijs; K. A. A. Makinwa;
     In Proc. IEEE International Workshop on Advances in Sensors and Interfaces (IWASI),
     IEEE, pp. 122‒125, June 2015. DOI: 10.1109/iwasi.2015.7184929

134. A 30ppm <80nJ ring-down-based readout circuit for resonant sensors
     H. Jiang; Z. Y. Chang; M. Pertijs;
     In Dig. Techn. Papers IEEE International Solid-State Circuits Conference (ISSCC),
     IEEE, pp. 482‒483, February 2015. DOI: 10.1109/ISSCC.2015.7063136
     
     Abstract: ...

     A readout circuit for MEMS resonant sensors, realized in 0.35μm CMOS, employs a dynamically-switching level-crossing detector to determine resonance frequency and quality factor from a single ring-down transient. Results obtained with three different resonators are in good agreement conventional impedance analysis. The circuit achieves a frequency resolution better than 30 ppm while consuming less than 80 nJ/meas from a 1.8V supply, 7.8x less than the state-of-the-art.

135. A 0.05mm² 1V capacitance-to-digital converter based on period modulation
     Y. He; Z. Y. Chang; L. Pakula; S. H. Shalmany; M. Pertijs;
     In Dig. Techn. Papers IEEE International Solid-State Circuits Conference (ISSCC),
     IEEE, pp. 486‒487, February 2015. DOI: 10.1109/ISSCC.2015.7063138
     
     Abstract: ...

     This paper presents a digitally assisted period modulation (PM)-based capacitance-to-digital converter (CDC) that is >9× smaller than prior CDCs with >10b resolution, and improves the energy efficiency by >10× compared to previous PM-based CDCs. This is achieved with the help of a piece-wise charge transfer technique that eliminates the need for a large on-chip integration capacitor, a dual-integration-capacitor scheme that reduces the front-end noise contribution, a sampled-biasing technique that reduces the noise of the integration current, and a current-efficient inverter-based design.

136. A mixed-signal multiplexing system for cable-count reduction in ultrasound probes
     Q. Liu; C. Chen; Z. Y. Chang; C. Prins; M. A. P. Pertijs;
     In Proc. IEEE International Ultrasonics Symposium (IUS),
     IEEE, pp. 1‒4, October 2015. DOI: 10.1109/ultsym.2015.0141
     
     Abstract: ...

     This paper presents an approach to time-multiplexing multiple receive signals in a miniature ultrasound probe onto a single micro-coaxial cable. The resulting reduction in the number of receive cables alleviates the design of high-element-count endoscope- or catheter-based ultrasound probes. A prototype multiplexing system is presented that employs a custom multiplexing chip that uses current-mode drivers to combine four receive channels, sampled at 25 MHz each, on a single 3-m micro-coaxial cable. On the system-side of the cable, a transimpedance amplifier turns the multiplexed signal back into a voltage, after which it is digitized and equalized to correct for channel-to-channel crosstalk due to non-idealities of the cable. The chip has been implemented in a 0.18 μm CMOS process and consumes less than 1 mW per input channel. Experimental results show that the system can successfully convey 6 MHz Gaussian-shaped pulses applied to the four input channels of the multiplexing chip to the system with a channel-to-channel crosstalk below -31 dB.

137. A single-cable PVDF transducer readout IC for intravascular photoacoustic imaging
     C. Chen; V. Daeichin; Q. Ding; G. van Soest; G. Springeling; T. van der Steen; M. Pertijs; N. de Jong;
     In Proc. IEEE International Ultrasonics Symposium (IUS),
     IEEE, pp. 1‒4, October 2015. DOI: 10.1109/ultsym.2015.0142
     
     Abstract: ...

     This paper presents a custom-designed single-cable readout IC for the reception of the broadband photoacoustic (PA) signal in intravascular photoacoustic (IVPA) imaging. The readout IC is intended for direct integration behind a broadband polyvinylidene fluoride (PVDF) transducer in an IVPA catheter tip to match the impedance between the small PVDF element and the connecting cable. The capability of the readout IC to work with a single cable that combines the output signal and the power supply ensures the mechanical flexibility of the IVPA catheter. Electrical measurements show that the readout IC provides a flat frequency response from 1 MHz to 20 MHz with a 6 mA external current supply. The acoustical measurements involving the readout IC and the PVDF transducer demonstrate a 60 dB dynamic range, a sensitivity of 3.8 μV/Pa at 2.25 MHz, and a broad receiving bandwidth from 2 MHz to 15 MHz.

138. Temperature sensor for a leadless cardiac pacemaker
     M. A. P. Pertijs; K. J. Carroll;
     Patent, United States 9,060,692, June 2015.

139. Highlights of the ISSCC 2013 Processors and High Performance Digital Sessions
     T. Fischer; B. G. Nam; L. Chang; T. Kuroda; M. A. P. Pertijs;
     IEEE Journal of Solid-State Circuits,
     Volume 49, Issue 1, pp. 4‒8, 2014. DOI: 10.1109/jssc.2013.2284658
     
     Abstract: ...

     This special issue covers the ISSCC conference held in San Francisco, CA, USA, on February 17-21, 2013. The issue includes the topics from the low power and high performance digital, memory, and technology directions as well as imagers, medical and sensors. There are 27 papers in the issue.

140. Smart sensor systems: Emerging technologies and applications
     G. Meijer; K. Makinwa; M. Pertijs;
     John Wiley \& Sons, , 2014.
     
     Abstract: ...

     With contributions from an internationally-renowned group of experts, this book uses a multidisciplinary approach to review recent developments in the field of smart sensor systems, covering important system and design aspects. It examines topics over the whole range of sensor technology from the theory and constraints of basic elements, physics and electronics, up to the level of application-orientated issues.
     
     document

141. Calibration and Self-Calibration of Smart Sensors
     M. Pertijs;
     In Smart Sensor Systems: Emerging Technologies and Applications,
     John Wiley \& Sons, May 2014.
     
     Abstract: ...

     Smart sensors acquire information about a non-electrical quantity of interest (the measurand) and convert this information to a useful electrical output signal. In order to do so, they combine a sensing element and the associated interface electronics on a single chip or in a single package. The sensing element performs the conversion from the non-electrical domain of the measurand to an electrical signal, while the interface electronics further process this signal to produce an output that can readily be used in a measurement or control system. Errors introduced in these steps affect the performance and reliability of the overall system. Therefore, it is very important to determine how large these errors are. The process of doing so is generally referred to as calibration, and is the topic of this chapter.
     
     document

142. Dedicated Impedance-Sensor Systems
     G. Meijer; X. Li; B. Iliev; G. Pop; Z. Y. Chang; S. Nihtianov; Z. Tan; A. Heidari; M. Pertijs;
     In Smart Sensor Systems: Emerging Technologies and Applications,
     John Wiley \& Sons, May 2014.
     
     Abstract: ...

     Impedance sensors can be defined as being a set of electrodes which can be used to measure electrical properties of materials or structures. Once these properties are known, it appears that the features of measurements performed with such sensors depend for a large part on the properties of the material or structure to be characterized and only partly on the characteristics of the electrodes. The electrical properties of the sensor in its application can be modeled with passive elements in equivalent electrical circuits. The challenging task for the designer is to make such a sensor system sensitive for the measurands and to obtain immunity for other parameters. In this chapter, we consider impedance sensors to be sensors in a certain measurement environment, and that in the electric model presentation of this setup there is at least one resistive or one reactive component of interest which has to be measured.
     
     document

143. Design of a Miniature Ultrasound Probe for 3D Transesophageal Echocardiography
     D. Bera; S. B. Raghunathan; C. Chen; S. Blaak; C. Prins; M. A. P. Pertijs; M. D. Verweij; J. G. Bosch; N. de Jong;
     In Annual Sensor Technology Workshop Sense of Contact,
     The Netherlands, April 2014.

144. An energy-efficient reconfigurable readout circuit for resonant sensors based on ring-down measurement
     Y. Yan; Z. Zeng; C. Chen; H. Jiang; Z. Y. Chang; D. M. Karabacak; M. A. P. Pertijs;
     In Proc. IEEE Sensors Conference,
     IEEE, pp. 221‒224, October 2014. DOI: 10.1109/icsens.2014.6984973

145. In-air ultrasonic gesture sensing with MEMS microphones
     D. M. van Willigen; E. Mostert; M. A. P. Pertijs;
     In Proc. IEEE Sensors Conference,
     IEEE, pp. 90‒93, October 2014. DOI: 10.1109/icsens.2014.6984940

146. An eddy-current displacement-to-digital converter based on a ratio-metric delta-sigma ADC
     A. Fekri; M. Nabavi; N. Radeljic-Jakic; Z. Y. Chang; M. Pertijs; S. Nihtianov;
     In Proc. European Solid-State Circuits Conference (ESSCIRC),
     IEEE, pp. 403‒406, September 2014. DOI: 10.1109/esscirc.2014.6942107

147. Capacitive sensor interface with precision references
     R. Yang; M. A. P. Pertijs; S. Nihtianov; P. Haak;
     In Proc. IEEE International Conference on Industrial Technology (ICIT),
     IEEE, pp. 358‒390, March 2014. DOI: 10.1109/icit.2014.6894896

148. Design of a miniature ultrasound probe for 3D transesophageal echocardiography
     S. B. Raghunathan; D. Bera; C. Chen; S. Blaak; C. Prins; M. A. P. Pertijs; J. G. Bosch; N. de Jong; M. D. Verweij;
     In Proc. IEEE International Ultrasonics Symposium (IUS),
     IEEE, pp. 2091‒2094, September 2014. DOI: 10.1109/ultsym.2014.0521
     
     Abstract: ...

     The relatively large size of most of the current 3D Transesophageal Echocardiography probes (TEE) enables their usage in adults for short procedures only. In this paper, we propose a new miniature 3D TEE probe with a head volume of 1 cm3, that would be suitable for use in neonates or for prolonged transnasal use in adults. We focus on partitioned designs, in which a minority of transmit elements is directly wired out and the majority of receive elements connect to a limited number of receive cables via an ASIC that performs a nine-fold data reduction in receive mode. The designs are motivated based on the pressure and beam width of the transmitted field, and the resolution, grating lobes and side lobes in the received field.

149. An interface for eddy-current displacement sensors with 15-bit resolution and 20 MHz excitation
     M. R. Nabavi; M. A. P. Pertijs; S. Nihtianov;
     IEEE Journal of Solid-State Circuits,
     Volume 48, Issue 11, pp. 2868‒2881, November 2013. DOI: 10.1109/jssc.2013.2281692
     
     Abstract: ...

     This paper presents an integrated interface for eddy-current sensors (ECSs) for displacement measurement. The employed architecture helps bridging the performance gap between the requirements of demanding and precision industrial applications and the performance of existing ECS interfaces. The interface operates with a sensor excitation frequency of 20 MHz, which is more than one order of magnitude higher than typical values. This high excitation frequency limits the eddy-current penetration depth in the target down to a few tens of micrometers, thus enabling the use of thin targets required in precision applications. The proposed interface consists of a low-power front-end oscillator that incorporates the sensor, and a two-channel offset-compensated synchronous demodulator. A ratio-metric measurement approach along with offset and 1/f noise reduction techniques is applied to improve the system stability. The interface has been realized in a 0.35-μm 3.3 V BiCMOS technology and consumes 18 mW. Measurement results obtained using two flat sensing coils show a full-range non-linearity of the sensor interface of only 0.4\%, and a resolution of 15.5 bits (65 nm on a 3 mm measurement range), with 1 kHz signal bandwidth. This translates into 1.5 pico-Henry inductance-measurement resolution, which is comparable with the performance of the most advanced LCR meters. Using the proposed solution, a long-term instability below 20 ppm (for 17 hours) and a thermal drift of 30 ppm/°C are obtained without any temperature compensation. Compared to the state-of-the-art, the proposed interface achieves a considerably better trade-off between power consumption, resolution, bandwidth, and excitation frequency.

150. A 1.2-V 8.3-nJ CMOS humidity sensor for RFID applications
     Z. Tan; R. Daamen; A. Humbert; Y. V. Ponomarev; Y. Chae; M. A. P. Pertijs;
     IEEE Journal of Solid-State Circuits,
     Volume 48, Issue 10, pp. 2469‒2477, October 2013. DOI: 10.1109/jssc.2013.2275661
     
     Abstract: ...

     This paper presents a fully integrated CMOS humidity sensor for a smart RFID sensor platform. The sensing element is a CMOS-compatible capacitive humidity sensor, which consists of top-metal finger-structure electrodes covered by a humidity-sensitive polyimide layer. Its humidity-sensitive capacitance is digitized by an energy-efficient capacitance-to-digital converter (CDC) based on a third-order delta-sigma modulator. This CDC employs current-efficient operational transconductance amplifiers based on current-starved cascoded inverters, whose limited output swing is accommodated by employing a feedforward loop-filter topology. A programmable offset capacitor is included to remove the sensor's baseline capacitance and thus reduce the required dynamic range. To reduce offset errors due to charge injection of the switches, the entire system is auto-zeroed. The proposed humidity sensor has been realized in a 0.16- μm CMOS technology. Measurement results show that the CDC performs a 12.5-bit capacitance-to-digital conversion in a measurement time of 0.8 ms, while consuming only 8.6 μA from a 1.2-V supply. This corresponds to a state-of-the-art figure-of-merit of 1.4 pJ/conversion-step. Combined with the co-integrated humidity sensing element, it provides a resolution of 0.05\% RH in the range from 30\% RH to 100\% RH while consuming only 8.3 nJ per measurement, which is an order-of-magnitude less energy than the state-of-the-art.

151. A Low-Power CMOS Smart Temperature Sensor with a Batch-Calibrated Inaccuracy of ±0.25°C (±3σ) from -70°C to 130°C
     A. Aita; M. Pertijs; K. Makinwa; J. Huijsing; G. Meijer;
     IEEE Sensors Journal,
     Volume 13, Issue 5, pp. 1840‒1848, May 2013. DOI: 10.1109/JSEN.2013.2244033
     
     Abstract: ...

     In this paper, a low-power CMOS smart temperature sensor is presented. The temperature information extracted using substrate PNP transistors is digitized with a resolution of 0.03°C using a precision switched-capacitor (SC) incremental ΔΣ A/D converter. After batch calibration, an inaccuracy of ±0.25°C (±3) from -70°C to 130°C is obtained. This represents a two-fold improvement compared to the state-of-the-art. After individual calibration at room temperature, an inaccuracy better than ±0.1°C over the military temperature range is obtained, which is in-line with the state-of-the-art. This performance is achieved at a power consumption of 65 μW during a measurement time of 100 ms, by optimizing the power/inaccuracy tradeoffs, and by employing a clock frequency proportional to absolute temperature. The latter ensures accurate settling of the SC input stage at low temperatures, and reduces the effects of leakage currents at high temperatures.

152. An energy-efficient readout circuit for resonant sensors based on ring-down measurement
     Z. Zeng; M. A. P. Pertijs; D. M. Karabacak;
     Review of Scientific Instruments,
     Volume 84, Issue 2, pp. 025005, February 2013. DOI: 10.1063/1.4792396
     
     Abstract: ...

     This paper presents an energy-efficient readout circuit for resonant sensors that operates based on a transient measurement method. The resonant sensor is driven at a frequency close to its resonance frequency by an excitation source that can be intermittently disconnected, causing the sensor to oscillate at its resonance frequency with exponentially decaying amplitude. By counting the zero crossings of this ring-down response, the interface circuit can detect the resonance frequency. In contrast with oscillator-based readout, the presented readout circuit is readily able to detect quality factor (Q) of the resonator from the envelope of the ring-down response, and can be used even in the presence of large parasitic capacitors. A prototype of the readout circuit has been integrated in 0.35 μm CMOS technology, and consumes only 36 μA from a 3.3 V supply during a measurement time of 2 ms. The resonance frequency and quality factor of a micro-machined SiN resonator obtained using this prototype are in good agreement with results obtained using impedance analysis. Furthermore, a clear transient response is observed to ethanol flow using the presented readout, demonstrating the use of this technique in sensing applications.

153. A 7μW pH-to-digital converter for quality monitoring of perishable products
     S. H. Shalmany; M. Merz; A. Fekri; Z. Chang; R. Hoofman; M. A. P. Pertijs;
     In Proc. International Conference on Solid-State Sensors, Actuators and Microsystems (TRANSDUCERS),
     IEEE, pp. 1747‒1750, June 2013. DOI: 10.1109/Transducers.2013.6627125
     
     Abstract: ...

     This paper describes an energy-efficient smart pH sensor intended for use in RFID tags to monitor the quality of perishable products. The sensor is based on an Extended Gate Field-Effect Transistor (EGFET). In a measurement time of 20 ms, it achieves a pH resolution of 0.05 and an accuracy of 0.1 in a pH range from 3 to 10, while consuming only 7 μW. This level of power consumption, which is orders of magnitude lower than the prior art, is achieved by incorporating the EGFET in an ultra-low-power frontend based on a differential source-follower, and digitizing the resulting pH-dependent voltage using an incremental first-order ΔΣ ADC.

154. A low-power CMOS integrated sensor for CO2 detection in the percentage range
     A. Humbert; B. J. Tuerlings; R. J. O. M. Hoofman; Z. Tan; D. Gravesteijn; M. A. P. Pertijs; C. W. M. Bastiaansen; D. Soccol;
     In Proc. International Conference on Solid-State Sensors, Actuators and Microsystems (TRANSDUCERS),
     IEEE, pp. 1649‒1652, June 2013. DOI: 10.1109/Transducers.2013.6627101
     
     Abstract: ...

     Within the Catrene project “PASTEUR”, a low-cost, low-power capacitive carbon dioxide sensor has been developed for tracking CO2 concentration in the percentage range. This paper describes this sensor, which operates at room temperature where it exhibits short response times as well as reversible behavior. It can be easily integrated using CMOS compatible processing, and has been combined with a Relative Humidity (RH) sensor, using the same capacitive transduction method, and with a low-power capacitance-to-digital converter, hence enabling correction of cross sensitivity to RH.

155. A 1V 14b self-timed zero-crossing-based incremental ΔΣ ADC
     C. Chen; Z. Tan; M. A. P. Pertijs;
     In Dig. Techn. Papers IEEE International Solid-State Circuits Conference (ISSCC),
     IEEE, pp. 274‒275, February 2013. DOI: 10.1109/ISSCC.2013.6487732
     
     Abstract: ...

     This paper introduces a clock-free self-timed incremental ΔΣ ADC. Unlike conventional ΔΣ ADCs, it does not require a dedicated clock signal, thus saving energy and reducing system complexity. As such, it has similar advantages as self-timed (or asynchronous) SAR ADCs. It is particularly suited for use in energy-constrained sensor applications, in which conversions of a quasistatic input signal are triggered by infrequent and possibly irregular external events. As it autonomously powers down upon completion of a conversion, it can adapt to a wide range of conversion rates in an energy-efficient way.

156. Ultra-low Energy CMOS Humidity Sensors for RFID Applications
     Z. Tan; R. Daamen; A. Humbert; Y. V. Ponomarev; Y. Chae; G. C. M. Meijer; M. A. P. Pertijs;
     In Annual Sensor Technology Workshop Sense of Contact,
     The Netherlands, April 2013. (Best Poster Award).

157. An energy-efficient 15-bit capacitive-sensor interface based on period modulation
     Z. Tan; S. H. Shalmany; G. C. M. Meijer; M. A. P. Pertijs;
     IEEE Journal of Solid-State Circuits,
     Volume 47, Issue 7, pp. 1703‒1711, July 2012. DOI: 10.1109/jssc.2012.2191212
     
     Abstract: ...

     This paper presents an energy-efficient capacitive-sensor interface with a period-modulated output signal. This interface converts the sensor capacitance to a time interval, which can be easily digitized by a simple digital counter. It is based on a relaxation oscillator consisting of an integrator and a comparator. To enable the use of a current-efficient telescopic OTA in the integrator, negative feedback loops are applied to limit the integrator's output swing. To obtain an accurate ratiometric output signal, auto-calibration is applied. This eliminates errors due to comparator delay, thus enabling the use of a low-power comparator. Based on an analysis of the stability of the negative feedback loops, it is shown how the current consumption of the interface can be traded for its ability to handle parasitic capacitors. A prototype fabricated in 0.35 μm standard CMOS technology can handle parasitic capacitors up to five times larger than the sensor capacitance. Experimental results show that it achieves 15-bit resolution and 12-bit linearity within a measurement time of 7.6 ms for sensor capacitances up to 6.8 pF, while consuming only 64 μA from a 3.3 V power supply. Compared to prior work with similar performance, this represents a significant improvement in energy efficiency.

158. Front-end receiver electronics for a matrix transducer for 3-D transesophageal echocardiography
     Z. Yu; S. Blaak; Z. Y. Chang; J. Yao; J. G. Bosch; C. Prins; C. T. Lancee; N. de Jong; M. A. P. Pertijs; G. C. M. Meijer;
     IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control,
     Volume 59, Issue 7, pp. 1500‒1512, July 2012. DOI: 10.1109/tuffc.2012.2350
     
     Abstract: ...

     There is a clear clinical need for creating 3-D images of the heart. One promising technique is the use of transesophageal echocardiography (TEE). To enable 3-D TEE, we are developing a miniature ultrasound probe containing a matrix piezoelectric transducer with more than 2000 elements. Because a gastroscopic tube cannot accommodate the cables needed to connect all transducer elements directly to an imaging system, a major challenge is to locally reduce the number of channels, while maintaining a sufficient signal-to-noise ratio. This can be achieved by using front-end receiver electronics bonded to the transducers to provide appropriate signal conditioning in the tip of the probe. This paper presents the design of such electronics, realizing time-gain compensation (TGC) and micro-beamforming using simple, low-power circuits. Prototypes of TGC amplifiers and micro-beamforming cells have been fabricated in 0.35-μm CMOS technology. These prototype chips have been combined on a printed circuit board (PCB) to form an ultrasound-receiver system capable of reading and combining the signals of three transducer elements. Experimental results show that this design is a suitable candidate for 3-D TEE.

159. Energy-Efficient Capacitive Sensor Interfaces
     M. A. P. Pertijs; Z. Tan;
     In Nyquist AD Converters, Sensor Interfaces, and Robustness,
     Springer Science \& Business Media, October 2012.
     
     Abstract: ...

     Capacitive sensor systems are potentially highly energy efficient. In practice, however, their energy consumption is typically dominated by that of the interface circuit that digitizes the sensor capacitance. Energy-efficient capacitive sensor interfaces are therefore a prerequisite for the successful application of capacitive sensors in energy-constrained applications, such as battery-powered devices and wireless sensor nodes. This paper derives lower bounds on the energy consumption of capacitive sensor interfaces. A comparison of these bounds with the state-of-the-art suggests that there is significant room for improvement. Several approaches to improving energy efficiency are discussed and illustrated by two design examples.
     
     document

160. A 1.2 V 8.3 nJ energy-efficient CMOS humidity sensor for RFID applications
     Z. Tan; Y. Chae; R. Daamen; A. Humbert; Y. V. Ponomarev; M. A. P. Pertijs;
     In Dig. Techn. Paper IEEE Symposium on VLSI Circuits (VLSI),
     IEEE, pp. 24‒25, June 2012. DOI: 10.1109/vlsic.2012.6243771

161. An energy-efficient interface for resonant sensors based on ring-down measurement
     M. A. P. Pertijs; Z. Zeng; D. M. Karabacak; M. Crego-Calama; S. H. Brongersma;
     In Proc. IEEE International Symposium on Circuits and Systems (ISCAS),
     IEEE, pp. 990‒993, May 2012. invited paper. DOI: 10.1109/iscas.2012.6272213

162. Energy-Efficient Capacitive Sensor Interfaces
     M. Pertijs; Z. Tan;
     In Proc. Workshop on Advances in Analog Circuit Design (AACD),
     March 2012. invited paper. DOI: 10.1007/978-1-4614-4587-6_8

163. A 9-channel low-power receiver ASIC for 3D transesophageal echocardiography
     Z. Yu; S. Blaak; C. Prins; Z. Y. Chang; C. T. Lancée; J. G. Bosch; N. de Jong; G. C. M. Meijer; M. A. P. Pertijs;
     In Proc. IEEE International Ultrasonics Symposium (IUS),
     IEEE, pp. 2063‒2066, October 2012. DOI: 10.1109/ultsym.2012.0516
     
     Abstract: ...

     This paper presents a 9-channel low-power receiver ASIC dedicated to a matrix piezoelectric ultrasound transducer for 3D Trans-Esophageal Echocardiography (TEE). It consists of 9 low-noise amplifiers (LNAs), 9 time-gain-compensation (TGC) amplifiers and a 9:1 micro-beamformer. A prototype ASIC has been implemented in 0.35 μm CMOS technology, with a core area of 0.98 mm × 1.7 mm. It is operated at a 3.3 V supply and consumes only 0.5 mW per channel. The measured channel-to-channel mismatch is within ±1 dB. Acoustic measurements proved the micro-beamforming function of the ASIC when processing real ultrasound signals from a 3 × 3 transducer array. These promising results show that this design, after layout optimization, is suitable to be scaled up to accommodate a full matrix transducer.

164. Oven Controlled MEMS Oscillator Device
     S. Donnay; X. Rottenberg; J. Borremans; H. Tilmans; G. van der Plas; M. Pertijs;
     Patent, United States 13/150,499, December 2012.

165. Oven controlled MEMS oscillator
     S. Donnay; X. Rottenberg; J. Borremans; H. Tilmans; G. van der Plas; M. Pertijs;
     Patent, European 2,530,836, December 2012.

166. Ultrasound beamformer using pipeline-operated S/H delay stages and charge-mode summation
     Z. Yu; M. A. P. Pertijs; G. C. M. Meijer;
     Electronics Letters,
     Volume 47, Issue 18, pp. 1011‒1012, September 2011. DOI: 10.1049/el.2011.1786
     
     Abstract: ...

     The proposed ultrasound beamformer is based on the delay-and-sum beamforming principle. The circuit consists of several programmable delay lines. Each delay line is constructed by pipeline-operated sample-and-hold (S/H) stages with digitally-assisted delay control, which ensure delay-independent gain and good timing accuracy. The summation is realised in the charge domain using the charge-averaging method, which consumes virtually no extra die area or power. A prototype beamformer has been fabricated in a 0.35 m CMOS process to interface nine transducer elements. Measurement results show that this circuit consumes much less power and chip area than the prior art, while maintaining good accuracy and flexibility.

167. A Single-Temperature Trimming Technique for MOS-Input Operational Amplifiers Achieving 0.33μV/°C Offset Drift
     M. Bolatkale; M. A. P. Pertijs; W. J. Kindt; J. H. Huijsing; K. A. A. Makinwa;
     IEEE Journal of Solid-State Circuits,
     Volume 46, Issue 9, pp. 2099‒2107, September 2011. DOI: 10.1109/JSSC.2011.2139530
     
     Abstract: ...

     A MOS-input operational amplifier has a reconfigurable input stage that enables trimming of both offset and offset drift based only on single-temperature measurements. The input stage consists of a MOS differential pair, whose offset drift is predicted from offset voltage measurements made at well-defined bias currents. A theoretical motivation for this approach is presented and validated experimentally by characterizing the offset of pairs of discrete MOS transistors as a function of bias current and temperature. An opamp using the proposed single-temperature trimming technique has been designed and fabricated in a 0.5 μm BiCMOS process. After single-temperature trimming, it achieves a maximum offset of ± 30 μV and an offset drift of 0.33 μV/°C (3σ) over the temperature range of -40°C to +125°C.

168. A Ratio-metric Analog to Digital Converter for an Eddy Current Displacement Sensor
     A. Fekri; M. R. Nabavi; M. Pertijs; S. Nihtianov;
     In Proc. International Scientific Conference on Electronics,
     Sozopol, Bulgaria, September 2011.

169. A 1.8V 11μW CMOS smart humidity sensor for RFID sensing applications
     Z. Tan; R. Daamen; A. Humbert; K. Souri; Y. Chae; Y. V. Ponomarev; M. A. P. Pertijs;
     In Proc. IEEE Asian Solid State Circuits Conference (A-SSCC),
     IEEE, pp. 105‒108, November 2011. DOI: 10.1109/ASSCC.2011.6123615
     
     Abstract: ...

     A fully-integrated humidity sensor for a smart RFID sensor platform has been realized in 0.16μm standard CMOS technology. It consists of a top-metal finger-structure capacitor covered with a humidity-sensitive layer, combined with a micro-power flexible sensor interface based on a second-order incremental delta-sigma converter. The interface can be easily reconfigured to compensate for process variation of the sensing element. In a measurement time of 10.2 ms, the interface performs a 13-bits capacitance-to-digital conversion while consuming only 5.85 μA from 1.8 V supply. In combination with the co-integrated sensor capacitor, it thus provides a humidity-to-digital conversion with a resolution of 0.1\% RH in the range of 20\% to 90\% RH at only 107 nJ per measurement. This represents a significant improvement in energy efficiency compared to existing capacitive-sensor interfaces with comparable performance.

170. Light-emitting diode junction-temperature sensing using differential voltage/current measurements
     F. D. Roscam-Abbing; M. A. P. Pertijs;
     In Proc. IEEE Sensors Conference,
     IEEE, pp. 861‒864, October 2011. DOI: 10.1109/icsens.2011.6127191

171. An energy-efficient 15-bit capacitive sensor interface
     Z. Tan; M. A. P. Pertijs; G. Meijer;
     In Proc. European Solid-State Circuits Conference (ESSCIRC),
     IEEE, pp. 283‒286, September 2011. DOI: 10.1109/esscirc.2011.6044962

172. A ping-pong-pang current-feedback instrumentation amplifier with 0.04\% gain error
     S. Sakunia; F. Witte; M. Pertijs; K. Makinwa;
     In Dig. Techn. Paper IEEE Symposium on VLSI Circuits (VLSI),
     IEEE, pp. 60‒61, June 2011.
     
     Abstract: ...

     A ping-pong-pang auto-zeroed and chopped current-feedback instrumentation amplifier (CFIA) uses three dynamically-matched input stages to achieve 0.04\% gain error, a 2.5× improvement over prior art. Its 4 μV offset and 28 nV/√Hz noise are achieved at 3.5× less supply current than a comparable ping-pong auto-zeroed CFIA.
     
     document

173. Ovenized System Containing Micro-Electromechanical Resonator
     J. Borremans; M. A. P. Pertijs;
     Patent, United States 20130127552A1, November 2011.

174. A Thermal-Diffusivity-Based Frequency Reference in Standard CMOS With an Absolute Inaccuracy of ±0.1\% From -55°C to 125°C
     S. M. Kashmiri; M. A. P. Pertijs; K. A. A. Makinwa;
     IEEE Journal of Solid-State Circuits,
     Volume 45, Issue 12, pp. 2510‒2520, December 2010. DOI: 10.1109/JSSC.2010.2076343
     
     Abstract: ...

     An on-chip frequency reference exploiting the well-defined thermal-diffusivity (TD) of IC-grade silicon has been realized in a standard 0.7 μm CMOS process. A frequency-locked loop (FLL) locks the frequency of a digitally controlled oscillator (DCO) to the process-insensitive phase shift of an electrothermal filter (ETF). The ETF's phase shift is determined by its geometry and by the thermal diffusivity of bulk silicon (D). The temperature dependence of is compensated for with the help of die-temperature information obtained by an on-chip band-gap temperature sensor. The resulting TD frequency reference has a nominal output frequency of 1.6 MHz and dissipates 7.8 mW from a 5 V supply. Measurements on 16 devices show that it has an absolute inaccuracy of ±0.1\% (σ = ±0.05\%) over the military temperature range (-55°C to 125°C ), with a worst case temperature coefficient of ± 11.2 ppm/°C.

175. A 140 dB-CMRR current-feedback instrumentation amplifier employing ping-pong auto-zeroing and chopping
     M. A. P. Pertijs; W. J. Kindt;
     IEEE Journal of Solid-State Circuits,
     Volume 45, Issue 10, pp. 2044‒2056, October 2010. DOI: 10.1109/jssc.2010.2060253
     
     Abstract: ...

     This paper presents a precision general-purpose current-feedback instrumentation amplifier (CFIA) that employs a combination of ping-pong auto-zeroing and chopping to cancel its offset and 1/f noise. A comparison of offset-cancellation techniques shows that neither chopping nor auto-zeroing is an ideal solution for general-purpose CFIAs, since chopping results in output ripple, and auto-zeroing is associated with increased low-frequency noise. The presented CFIA mitigates these unintended side effects through a combination of these techniques. A ping-pong auto-zeroed input stage with slow-settling offset-nulling loops is applied to limit the bandwidth of the increased noise to less than half of the auto-zeroing frequency. This noise is then modulated away from DC by chopping the input stage at half the auto-zeroing frequency, reducing the low-frequency noise to the 27 nV/ white-noise level, without introducing extra output ripple. The auto-zeroing is augmented with settling phases to further reduce output transients. The CFIA was realized in a 0.5 μm analog CMOS process and achieves a typical offset of 2.8 μV and a CMRR of 140 dB in a common-mode voltage range that includes the negative supply.

176. Low-cost calibration techniques for smart temperature sensors
     M. A. P. Pertijs; A. L. Aita; K. A. A. Makinwa; J. H. Huijsing;
     IEEE Sensors Journal,
     Volume 10, Issue 6, pp. 1098‒1105, June 2010. DOI: 10.1109/jsen.2010.2040730
     
     Abstract: ...

     Smart temperature sensors generally need to be trimmed to obtain measurement errors below ±2°C. The associated temperature calibration procedure is time consuming and therefore costly. This paper presents two, much faster, voltage calibration techniques. Both make use of the fact that a voltage proportional to absolute temperature (PTAT) can be accurately generated on chip. By measuring this voltage, the sensor's actual temperature can be determined, whereupon the sensor can be trimmed to correct for its dominant source of error: spread in the on-chip voltage reference. The first calibration technique consists of measuring the (small) PTAT voltage directly, while the second, more robust alternative does so indirectly, by using an external reference voltage and the on-chip ADC. Experimental results from a prototype fabricated in 0.7 μm CMOS technology show that after calibration and trimming, these two techniques result in measurement errors (±3σ) of ±0.15°C and ±0.25°C, respectively, in a range from -55°C to 125°C.

177. 12-bit accurate voltage-sensing ADC with curvature-corrected dynamic reference
     N. Saputra; M. A. P. Pertijs; K. A. A. Makinwa; J. H. Huijsing;
     Electronics Letters,
     Volume 46, Issue 6, pp. 397‒398, March 2010. DOI: 10.1049/el.2010.3337
     
     Abstract: ...

     A sigma-delta analogue-to-digital converter (ADC) with a dynamic voltage reference is presented that achieves 12-bit absolute accuracy over the extended industrial temperature range (-40 to 105°C). Temperature-dependent gain errors due to the reference's curvature are digitally corrected by adjusting the gain of the ADC's decimation filter. The required correction factor is obtained by first using the reference to make a temperature measurement, and then translating the result into a correction factor by means of a lookup table and a linear interpolator. Thus, a dynamic voltage reference is realised with a measured temperature drift of less than 1.7 ppm/°C. The ADC was fabricated in 0.7 μm CMOS technology and consumes 85 μA from a 2.5-5.5 V supply.

178. Design of a Beamformer for an Ultrasonic Matrix Transducer for 3D Transesophageal Echocardiography
     Z. Yu; S. Blaak; G. C. M. Meijer; M. A. P. Pertijs; C. T. Lancée; J. G. Bosch; C. Prins; N. de Jong;
     In Annual Sensor Technology Workshop Sense of Contact,
     The Netherlands, April 2010. (Best Poster Award).

179. Energy-efficient capacitive sensor interface with high dynamic range
     Z. Tan; M. A. P. Pertijs; G. C. M. Meijer;
     In Annual Sensor Technology Workshop Sense of Contact,
     The Netherlands, April 2010.

180. A programmable analog delay line for Micro-beamforming in a transesophageal ultrasound probe
     Z. Yu; M. A. P. Pertijs; G. C. M. Meijer;
     In Proc. IEEE International Conference on Solid-State and Integrated Circuit Technology (ICSICT),
     IEEE, pp. 299‒301, November 2010. DOI: 10.1109/icsict.2010.5667749

181. An interface for eddy current displacement sensors with 15-bit resolution and 20 MHz excitation
     M. R. Nabavi; M. A. P. Pertijs; S. Nihtianov;
     In Proc. European Solid-State Circuits Conference (ESSCIRC),
     IEEE, pp. 290‒293, September 2010. DOI: 10.1109/esscirc.2010.5619835

182. A Thermal-diffusivity-based Frequency Reference in Standard CMOS with an Absolute Inaccuracy of ±0.1\% from -55°C to 125°C
     M. Kashmiri; M. Pertijs; K. Makinwa;
     In Dig. Techn. Papers IEEE International Solid-State Circuits Conference (ISSCC),
     IEEE, pp. 74‒75, February 2010. DOI: 10.1109/ISSCC.2010.5434042
     
     Abstract: ...

     Most electronic systems require a frequency reference, and so, much research has been devoted to the realization of on-chip frequency references in standard CMOS. However, the accuracy of such references is limited by the process spread and temperature drift of on-chip components. By means of trimming and temperature compensation, RC and ring oscillators have achieved inaccuracies in the order of 1\%. LC oscillators achieve inaccuracies below 0.1\%, but dissipate much more power. This paper describes a new approach, which exploits the well-defined thermal diffusivity of IC-grade silicon in order to generate frequencies stable to 0.1\% over process and temperature variations. Such thermal diffusivity (TD) frequency references dissipate less power than LC oscillators, are more accurate than RC and ring oscillators and, uniquely, scale well with process.

183. Design of a low power time-gain-compensation amplifier for a 2D piezoelectric ultrasound transducer
     J. Yao; Z. Yu; M. A. P. Pertijs; G. C. M. Meijer; C. T. Lancee; J. G. Bosch; N. de Jong;
     In Proc. IEEE International Ultrasonics Symposium (IUS),
     IEEE, pp. 841‒844, October 2010. DOI: 10.1109/ultsym.2010.5935775
     
     Abstract: ...

     In this paper, a programmable time-gain compensation amplifier dedicated to a 2D piezoelectric ultrasound transducer is presented. It uses an open-loop amplifier structure consisting of a voltage-to-current converter and a current-to-voltage converter. The circuit has been designed in a standard 0.35-μm CMOS process. Simulation and measurement results show that gains of 0dB, 12dB, 26dB and 40dB can be achieved for input signals centered at 6MHz with 80dB dynamic range (100μV to 1V). The measured gain errors at 6MHz are below 1dB for all gain settings. The amplifier consumes only 130μW when driving a 250fF load.

184. Chopped auto-zeroed ping-pong amplifier and related apparatus, system, and method
     M. A. P. Pertijs;
     Patent, United States 7,834,685, November 2010.

185. Current sense amplifier with extended common mode voltage range
     W. J. Kindt; M. A. P. Pertijs;
     Patent, United States 7,671,677, March 2010.

186. Digital temperature sensors and calibration thereof
     M. Pertijs; J. Huijsing;
     Patent, United States 7,674,035, March 2010.

187. Digitale temperatursensoren und kalibrierung dafür
     M. A. P. Pertijs; J. H. Huijsing;
     Patent, German 602,005,020,159, May 2010.

188. Autozeroing current feedback instrumentation amplifier
     M. Pertijs; G. Reitsma;
     Patent, United States 7,719,351, May 2010.

189. Integrated circuit with pin-selectable mode of operation and level-shift functionality and related apparatus, system, and method
     M. A. P. Pertijs;
     Patent, United States 7,714,612, May 2010.

190. Bias-steuerung
     M. A. P. Pertijs; J. H. Huijsing;
     Patent, German 602,005,018,235, January 2010.

191. A 140dB-CMRR current-feedback instrumentation amplifier employing ping-pong auto-zeroing and chopping
     M. A. P. Pertijs; W. J. Kindt;
     In Highlights of ISSCC 2009,
     Eindhoven, The Netherlands, March 2009.

192. A 140dB-CMRR current-feedback instrumentation amplifier employing ping-pong auto-zeroing and chopping
     M. A. P. Pertijs; W. J. Kindt;
     In Dig. Techn. Papers IEEE International Solid-State Circuits Conference (ISSCC),
     IEEE, pp. 324‒325, February 2009. DOI: 10.1109/isscc.2009.4977439

193. A CMOS smart temperature sensor with a batch-calibrated inaccuracy of ±0.25°C (3σ) from -70°C to 130°C
     A. L. Aita; M. Pertijs; K. Makinwa; J. H. Huijsing;
     In Dig. Techn. Papers IEEE International Solid-State Circuits Conference (ISSCC),
     IEEE, pp. 342‒343, February 2009. DOI: 10.1109/ISSCC.2009.4977448
     
     Abstract: ...

     A major contributor to the total cost of precision CMOS temperature sensors is the cost of trimming and calibration. Significant cost savings can be obtained by batch calibration, but this is usually at the expense of an equally significant loss of accuracy. This paper presents a CMOS temperature sensor with a batch-calibrated inaccuracy of ±0.25°C (3σ) from -70°C to 130°C, which represents a 2x improvement over the state of the art. Individual trimming reduces the sensor's inaccuracy to ±0.1°C (3σ) over the military range: -55°C to 125°C. The sensor draws 25μA from a 2.5V to 5.5V supply, which is significantly less than commercial products with comparable accuracy.

194. Autozeroing current feedback instrumentation amplifier
     M. Pertijs; G. Reitsma;
     Patent, United States 7,573,327, August 2009.

195. Strom-Rückkopplungs-Instrumentenverstärker mit selbsttätiger Nullpunkt-Einstellung
     M. Pertijs; G. Reitsma;
     Patent, German 102,008,023,384, January 2009.

196. Voltage calibration of smart temperature sensors
     M. A. P. Pertijs; A. L. Aita; K. A. A. Makinwa; J. H. Huijsing;
     In Proc. IEEE Sensors Conference,
     IEEE, pp. 756‒759, October 2008. DOI: 10.1109/icsens.2008.4716551

197. Sigma delta ADC with a dynamic reference for accurate temperature and voltage sensing
     N. Saputra; M. A. P. Pertijs; K. A. A. Makinwa; J. H. Huijsing;
     In Proc. IEEE International Symposium on Circuits and Systems (ISCAS),
     IEEE, pp. 1208‒1211, May 2008. DOI: 10.1109/iscas.2008.4541641

198. A BiCMOS Operational Amplifier Achieving 0.33μV/°C Offset Drift using Room-Temperature Trimming
     M. Bolatkale; M. A. P. Pertijs; W. J. Kindt; J. H. Huijsing; K. A. A. Makinwa;
     In Dig. Techn. Papers IEEE International Solid-State Circuits Conference (ISSCC),
     IEEE, pp. 76‒77, February 2008. DOI: 10.1109/isscc.2008.4523064

199. Bias circuits
     M. Pertijs; J. Huijsing;
     Patent, United States 7,446,598, November 2008.

200. Bitstream controlled reference signal generation for a sigma-delta modulator
     M. A. P. Pertijs; K. A. A. Makinwa; J. H. Huijsing;
     Patent, United States 7,391,351, June 2008.

201. Smart sensor design: the art of compensation and cancellation
     K. A. A. Makinwa; M. A. P. Pertijs; J. C. van der Meer; J. H. Huijsing;
     In Proc. European Solid-State Circuits Conference (ESSCIRC),
     IEEE, pp. 76‒82, September 2007. DOI: 10.1109/esscirc.2007.4430251

202. Precision temperature sensors in CMOS technology
     M. A. P. Pertijs; J. H. Huijsing;
     Springer Science \& Business Media, , 2006.
     
     Abstract: ...

     The low cost and direct digital output of CMOS smart temperature sensors are important advantages compared to conventional temperature sensors. This book addresses the main problem that nevertheless prevents widespread application of CMOS smart temperature sensors: their relatively poor absolute accuracy. Several new techniques are introduced to improve this accuracy. The effectiveness of these techniques is demonstrated using three prototypes. The final prototype achieves an inaccuracy of ±0.1 °C over the military temperature range, which is a significant improvement in the state of the art. Since smart temperature sensors have been the subject of academic and industrial research for more than two decades, an overview of existing knowledge and techniques is also provided throughout the book.
     
     document

203. Sigma Delta ADC with Accurate Dynamic Reference for Temperature Sensing and Voltage Monitoring
     N. Saputra; M. A. P. Pertijs; K. A. A. Makinwa; J. H. Huijsing;
     In Annual Workshop on Circuits, Systems and Signal Processing (ProRISC),
     The Netherlands, pp. 80‒84, November 2006.

204. A CMOS smart temperature sensor with a 3σ inaccuracy of ±0.1°C from -55°C to 125°C
     M. A. P. Pertijs; K. A. A. Makinwa; J. H. Huijsing;
     IEEE Journal of Solid-State Circuits,
     Volume 40, Issue 12, pp. 2805‒2815, December 2005. (JSSC Best Paper Award). DOI: 10.1109/JSSC.2005.858476
     
     Abstract: ...

     A smart temperature sensor in 0.7 μm CMOS is accurate to within ±0.1°C (3σ) over the full military temperature range of -55°C to 125°C. The sensor uses substrate PNP transistors to measure temperature. Errors resulting from nonidealities in the readout circuitry are reduced to the 0.01°C level. This is achieved by using dynamic element matching, a chopped current-gain independent PTAT bias circuit, and a low-offset second-order sigma-delta ADC that combines chopping and correlated double sampling. Spread of the base-emitter voltage characteristics of the substrate PNP transistors is compensated by trimming, based on a calibration at one temperature. A high trimming resolution is obtained by using a sigma-delta current DAC to fine-tune the bias current of the bipolar transistors.

205. A CMOS smart temperature sensor with a 3σ inaccuracy of ±0.5°C from -50°C to 120°C
     M. A. P. Pertijs; A. Niederkorn; X. Ma; B. McKillop; A. Bakker; J. H. Huijsing;
     IEEE Journal of Solid-State Circuits,
     Volume 40, Issue 2, pp. 454‒461, February 2005. DOI: 10.1109/JSSC.2004.841013
     
     Abstract: ...

     A low-cost temperature sensor with on-chip sigma-delta ADC and digital bus interface was realized in a 0.5 μm CMOS process. Substrate PNP transistors are used for temperature sensing and for generating the ADC's reference voltage. To obtain a high initial accuracy in the readout circuitry, chopper amplifiers and dynamic element matching are used. High linearity is obtained by using second-order curvature correction. With these measures, the sensor's temperature error is dominated by spread on the base-emitter voltage of the PNP transistors. This is trimmed after packaging by comparing the sensor's output with the die temperature measured using an extra on-chip calibration transistor. Compared to traditional calibration techniques, this procedure is much faster and therefore reduces production costs. The sensor is accurate to within ±0.5°C (3σ) from -50°C to 120°C.

206. Precision interface electronics for a CMOS smart temperature sensor
     M. A. P. Pertijs; J. H. Huijsing;
     In Proc. IEEE Sensors Conference,
     IEEE, pp. 4‒pp, October 2005. invited paper. DOI: 10.1109/ICSENS.2005.1597856
     
     Abstract: ...

     This paper describes the interface electronics of a CMOS smart temperature sensor that is accurate to plusmn0.1degC over the full military temperature range. The sensor is fabricated in a standard CMOS process. Substrate bipolar transistors are used as temperature-sensitive devices. Precision interface electronics are used to make the most of their temperature characteristics. While the sensor is trimmed at one temperature, its accuracy over the full temperature range depends on the initial accuracy of the electronics. Dynamic offset cancellation and dynamic element matching are used to eliminate offset and gain errors. These techniques are combined with a sigma-delta ADC to obtain a readily usable digital temperature reading

207. A CMOS temperature sensor with a 3σ inaccuracy of ±0.1°C from -55°C to 125°C
     M. Pertijs; K. Makinwa; J. Huijsing;
     In Dig. Techn. Papers IEEE International Solid-State Circuits Conference (ISSCC),
     IEEE, pp. 238‒596, February 2005. ({ISSCC} 2005 {Jack} {Kilby} Award for Outstanding Student Paper). DOI: 10.1109/ISSCC.2005.1493957
     
     Abstract: ...

     A smart temperature sensor is accurate to within ±0.1°C (3σ) over the full military temperature range of -55°C to 125°C. This 5x improvement is achieved using DEM, a current-gain independent PTAT bias circuit, and a low-offset ΔΣ ADC combining chopping and CDS. The sensor is fabricated in 0.7μm 2M1P CMOS with 4.5mm² area and draws 75μA.

208. Precision temperature measurement using CMOS substrate PNP transistors
     M. A. P. Pertijs; G. C. M. Meijer; J. H. Huijsing;
     IEEE Sensors Journal,
     Volume 4, Issue 3, pp. 294‒300, June 2004. DOI: 10.1109/jsen.2004.826742
     
     Abstract: ...

     This paper analyzes the nonidealities of temperature sensors based on substrate pnp transistors and shows how their influence can be minimized. It focuses on temperature measurement using the difference between the base-emitter voltages of a transistor operated at two current densities. This difference is proportional to absolute temperature (PTAT). The effects of series resistance, current-gain variation, high-level injection, and the Early effect on the accuracy of this PTAT voltage are discussed. The results of measurements made on substrate pnp transistors in a standard 0.5μm CMOS process are presented to illustrate the effects of these nonidealities. It is shown that the modeling of the PTAT voltage can be improved by taking the temperature dependency of the effective emission coefficient into account using the reverse Early effect. With this refinement, the temperature can be extracted from the measurement data with an absolute accuracy of ±0.1°C in the range of -50 to 130°C.

209. Low-cost calibration techniques for smart temperature sensors
     M. A. P. Pertijs; J. H. Huijsing;
     In Annual Sensor Technology Workshop Sense of Contact,
     The Netherlands, pp. 17, March 2004.

210. A CMOS Semi-Custom Chip for Mixed Signal Designs
     A. J. van Genderen; S. D. Cotofana; G. de Graaf; A. Kaichouhi; J. Liedorp; R. Nouta; M. A. P. Pertijs; C. J. M. Verhoeven;
     In Annual Workshop on Circuits, Systems and Signal Processing (ProRISC),
     The Netherlands, pp. 491‒496, November 2004.

211. Bitstream trimming of a smart temperature sensor
     M. A. P. Pertijs; J. H. Huijsing;
     In Proc. IEEE Sensors Conference,
     IEEE, pp. 904‒907, October 2004. DOI: 10.1109/ICSENS.2004.1426317
     
     Abstract: ...

     The paper presents a high-resolution trimming technique for use in precision smart temperature sensors. A digital sigma-delta modulator is used to trim the bias current of a bipolar transistor to compensate for process spread. In contrast with conventional trimming techniques, only a small chip area is required. The implementation of this technique in a temperature sensor with a sigma-delta ADC is discussed. On a prototype realized in 0.7μm CMOS, an 8-bit trimming resolution was measured, corresponding to 0.02°C on a range of 4.5°C.

212. A second-order sigma-delta ADC using MOS capacitors for smart sensor applications
     M. A. P. Pertijs; A. Bakker; J. H. Huijsing;
     In Proc. IEEE Sensors Conference,
     IEEE, pp. 421‒424, October 2004. DOI: 10.1109/ICSENS.2004.1426189
     
     Abstract: ...

     This paper presents a second-order sigma-delta ADC designed for use in a smart temperature sensor. It is operated in a 'one-shot' mode, i.e. the converter is powered up, produces a single conversion result, and powers down again. This paper discusses the implications of this mode of operation for the design of the modulator and the decimation filter. A sinc² decimation filter is used, which is shown to provide a higher resolution then a more complex sinc³ with the same conversion time. Through continuous-time integration of the input and reference voltages, the use of a linear sampling capacitor at the input is avoided. The modulator was implemented in a 0.5μm digital CMOS process using MOS capacitors. An effective resolution of 15.5 bits was measured with a conversion time of 25 ms.

213. A sigma-delta modulator with bitstream-controlled dynamic element matching
     M. A. P. Pertijs; J. H. Huijsing;
     In Proc. European Solid-State Circuits Conference (ESSCIRC),
     IEEE, pp. 187‒190, September 2004. DOI: 10.1109/ESSCIR.2004.1356649
     
     Abstract: ...

     When dynamic element matching (DEM) techniques are applied to generate a precision reference for a (single-bit) sigma-delta modulator, intermodulation occurs between the DEM residuals and the bitstream, which increases the in-band quantization noise. This can be prevented by deriving the sequence of DEM steps from the bitstream. This technique has been implemented in a second-order sigma-delta modulator with a dynamic bandgap voltage reference, which was realized in a 0.7μm CMOS process. Measurements show complete elimination of intermodulation products in the signal band, corresponding to an 8 dB reduction in quantization noise compared to conventional cyclic DEM.

214. A high-accuracy CMOS smart temperature sensor with fast calibration procedure
     M. A. P. Pertijs; A. Niederkorn; X. Ma; B. McKillop; A. Bakker; J. Huijsing;
     In Annual Sensor Technology Workshop Sense of Contact,
     The Netherlands, pp. 37, March 2003.

215. A CMOS temperature sensor with a 3σ inaccuracy of ±0.5°C from -50°C to 120°C
     M. Pertijs; A. Niederkorn; X. Ma; B. McKillop; A. Bakker; J. Huijsing;
     In Dig. Techn. Papers IEEE International Solid-State Circuits Conference (ISSCC),
     IEEE, pp. 200‒201, February 2003. DOI: 10.1109/ISSCC.2003.1234266
     
     Abstract: ...

     A temperature sensor in 0.5μm CMOS achieves an accuracy of ±0.5°C (3σ) from -50°C to 120°C. It combines chopping, dynamic element matching and curvature correction with calibration at room temperature. Calibration time has been reduced to less than 1s by using an on-chip transistor to measure the die temperature.

216. Calibration of Smart Temperature Sensors Using an On-Chip Transistor as Reference Thermometer
     M. A. P. Pertijs; J. H. Huijsing;
     In Annual Workshop on Semiconductor Sensors (SeSens),
     The Netherlands, pp. 657-661, November 2002.

217. Calibration and self-calibration of smart sensors
     M. A. P. Pertijs;
     In Proc. NMI Workshop Internet Measurement and Self-Calibration,
     The Netherlands, May 2002.

218. Non-idealities of temperature sensors using substrate PNP transistors
     M. A. P. Pertijs; G. C. M. Meijer; J. H. Huijsing;
     In Proc. IEEE Sensors Conference,
     IEEE, pp. 1018‒1023, June 2002. DOI: 10.1109/ICSENS.2002.1037251
     
     Abstract: ...

     This paper describes the nonidealities of temperature sensors based on substrate pnp transistors and shows how their influence can be minimized The effects of series resistance, current-gain variation, high-level injection and the Early effect on the accuracy of the PTAT voltage are discussed. The results of measurements made on substrate pnp transistors in a standard 0.5μm CMOS process are presented to show the effects of these nonidealities. It is shown that the modeling of the PTAT voltage can be improved by taking the temperature dependency of the effective emission coefficient into account using the reverse Early effect. With this refinement, the temperature can be extracted from the measurement data with an absolute accuracy of ±0.1°C in the range of -50°C to 130°C.

219. Transistor temperature measurement for calibration of integrated temperature sensors
     M. A. P. Pertijs; J. H. Huijsing;
     In Proc. IEEE Instrumentation and Measurement Technology Conference (IMTC),
     IEEE, pp. 755‒758, May 2002. DOI: 10.1109/IMTC.2002.1006936
     
     Abstract: ...

     A temperature measurement technique is presented for calibrating packaged integrated temperature sensors. An on-chip bipolar transistor is used to accurately determine the sensor's temperature during calibration. The transistor's base-emitter voltage is measured at three collector currents to find the absolute temperature while compensating for series resistances. The technique does not increase the pin count for a typical smart sensor, as the transistor can be accessed via the supply pins and an existing digital input pin. Measurements on substrate pnp's in a standard CMOS process show that the temperature can be determined with an accuracy of ±0.1°C in the range of -50°C to 130°C.

220. Non-linear signal correction
     M. A. P. Pertijs; A. Bakker; J. H. Huijsing;
     Patent, United States 6,456,145, September 2002.

221. A batch-calibrated smart temperature sensor with second-order curvature correction
     M. A. P. Pertijs; A. Bakker; J. H. Huijsing;
     In Annual Workshop on Semiconductor Sensors (SeSens),
     The Netherlands, pp. 852‒855, November 2001.

222. An Accurate CMOS Smart Temperature Sensor with Dynamic Element Matching and Second-Order Curvature Correction
     M. A. P. Pertijs; A. Bakker; J. H. Huijsing;
     In Proc. International Conference on Solid-State Sensors, Actuators and Microsystems (TRANSDUCERS),
     Springer Berlin Heidelberg, pp. 80‒83, June 2001. DOI: 10.1007/978-3-642-59497-7_18
     
     Abstract: ...

     A CMOS temperature sensor with digital bus interface is presented that combines dynamic element matching and second-order curvature correction to improve the accuracy. An error analysis is presented which shows that the remaining inaccuracy is determined by the process spread of substrate bipolar transistors. This spread is significantly less within a batch than between batches. Therefore, all sensors within a batch can be calibrated in the same way, leading to a three-sigma accuracy of ±1.5°C in the range of −50 to 120°C.

223. A high-accuracy temperature sensor with second-order curvature correction and digital bus interface
     M. A. P. Pertijs; A. Bakker; J. H. Huijsing;
     In Proc. IEEE International Symposium on Circuits and Systems (ISCAS),
     IEEE, pp. 368‒371, May 2001. DOI: 10.1109/ISCAS.2001.921869
     
     Abstract: ...

     A high-accuracy CMOS temperature sensor with integrated bus interface is presented. It is shown that when offset cancellation and dynamic element matching techniques are applied, the accuracy of the sensor is mainly limited by process spread between batches on the substrate bipolar transistors. Therefore, the sensors can be calibrated per batch instead of per sensor. In combination with a second-order curvature correction technique, this results in a three-sigma accuracy of ±1.5°C over the full temperature range.

224. Non-linear signal correction
     M. A. P. Pertijs; A. Bakker; J. H. Huijsing;
     Patent, WO PCT/EP2001/011,288, September 2001.

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