dr. Zhao Chen

1. A 2000-volumes/s 3-D Ultrasound Probe With Monolithically-Integrated 23 $\times$ 23-mm2 4096-Element CMUT Array
   Rozsa, Nuriel N. M.; Chen, Zhao; Kim, Taehoon; Guo, Peng; Hopf, Yannick M.; Voorneveld, Jason; dos Santos, Djalma Simoes; Noothout, Emile; Chang, Zu-Yao; Chen, Chao; Henneken, Vincent A.; de Jong, Nico; Vos, Hendrik J.; Bosch, Johan G.; Verweij, Martin D.; Pertijs, Michiel A. P.;
   IEEE Journal of Solid-State Circuits,
   pp. 1--14, 2025. early access. DOI: 10.1109/JSSC.2025.3534087
   
   Abstract: ...

   This article presents a 4096-element ultrasound probe for high volume-rate (HVR) cardiovascular imaging. The probe consists of two application-specific integrated circuits (ASICs), each of which interfaces with a 2048-element monolithically-integrated capacitive micro-machined ultrasound transducer (CMUT) array. The probe can image a 60∘ × 60∘ × 10-cm volume at 2000 volumes/s, the highest volume-rate with in-probe channel-count reduction reported to date. It uses 2 × 2 delay-and-sum micro-beamforming (μBF) and 2× time-division multiplexing (TDM) to achieve an 8× receive (RX) channel-count reduction. Equalization, trained using a pseudorandom bit-sequence generated on the chip, reduces TDM-induced crosstalk by 10 dB, enabling power-efficient scaling of the cable drivers. The ASICs also implement a novel transmit (TX) beamformer (BF) that operates as a programmable digital pipeline, which enables steering of arbitrary pulse-density modulated (PDM) waveforms. The TX BF drives element-level 65 V unipolar pulsers, which in turn drive the CMUT array. Both the TX BF and RX μBF are programmed with shift-registers (SRs) that can either be programmed in a row-column fashion for fast upload times, or daisy-chain fashion for a higher flexibility. The layout of the ASICs is matched to the 365-μm-pitch monolithically-integrated CMUT array. While operating, the RX and logic power consumption per element is 0.85 and 0.10 mW, respectively. TX power consumption is highly waveform dependent, but is nominally 0.34 mW. Compared to the prior art, the probe has the highest volume rate, and features among the largest imaging arrays (both in terms of element-count and aperture) with a high flexibility in defining the TX waveform. These properties make it a suitable option for applications requiring HVR imaging of a large region of interest.

2. An Amplitude-Programmable Energy-Recycling High-Voltage Resonant Pulser for Battery-Powered Ultrasound Devices
   Bellouki, Imad; Rozsa, Nuriel N. M.; Chang, Zu-Yao; Chen, Zhao; Tan, Mingliang; Pertijs, Michiel A. P.;
   IEEE Journal of Solid-State Circuits,
   pp. 1--12, 2024. Early Access. DOI: 10.1109/JSSC.2024.3494536
   
   Abstract: ...

   This article presents an application-specific integrated circuit (ASIC) for battery-powered ultrasound (US) devices. The ASIC implements a novel energy-efficient high-voltage (HV) pulser that generates HV transmit (TX) pulses directly from a low-voltage (LV) battery supply. By means of a single off-chip inductor, energy is supplied to a US transducer in a resonant fashion, directly generating half-period sinusoidal HV pulses on the transducer, while consuming substantially less energy than a conventional class-D pulser. By recycling residual reactive energy from the transducer back to the input, the energy consumption is further reduced by more than 50%. The autocalibration techniques are leveraged to deal with tolerances of the inductor, transducer, and battery supply and thus maximize the energy efficiency. A prototype chip was fabricated in TSMC 0.18-μm HV BCD technology and used to drive external 120pF capacitive micromachined US transducers (CMUTs) with a center frequency of approximately 2.5 MHz. Electrical measurements show that the prototype can generate pulses with a peak amplitude between 10 and 30 V accurate to within ±1 V. Acoustic measurements demonstrate successful ultrasonic pulse transmission and pulse-echo measurements. The prototype reaches a peak efficiency of 0.23 fCV2, which is the highest reported to date for HV pulsers targeting US imaging.

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 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),
   IEEE, pp. 1--2, June 2024. DOI: 10.1109/VLSITechnologyandCir46783.2024.10631363

4. An ASIC for Efficient Generation of High-Voltage Transmit Pulses for Battery-Powered Ultrasound Devices
   Imad Bellouki; Nuriel Rozsa; Zu-Yao Chang; Zhao Chen; Mingliang Tan; Michiel Pertijs;
   In Annual Workshop on Circuits, Systems and Signal Processing (ProRISC),
   July 2024.

5. A 3D Ultrasound Probe with Monolithically-Integrated 4096-Element CMUT Array Imaging 60° x 60° x 10cm at 2000 Volumes/s
   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 Annual Workshop on Circuits, Systems and Signal Processing (ProRISC),
   July 2024.

6. A 3D Ultrasound Probe with Monolithically-Integrated 4096-Element CMUT Array Imaging 60° x 60° x 10cm at 2000 Volumes/s
   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 Proc. IEEE International Ultrasonics Symposium (IUS),
   IEEE, September 2024. abstract, Best Student Paper Award.

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