From Murmann Mixed-Signal Group
BESS, Electical Engineering, National Chiao-Tung University, 2008
M.S, Electrical Engineering, Stanford University, 2011
Admitted to Ph.D. Candidacy: 2010-2011
Research: Front-end Electronics for Medical Ultrasound Imaging
Tremendous work has been done to carry conventional 2D ultrasonic imaging system to a portable 3D imaging system. In order to deal with high complexity of signal interface while achieving miniaturization, functional blocks need to be optimized in a system level perspective. Photoacoustic imaging, which can be considered as a received-only ultrasonic system, is the driver application in this research.
Conventional front-ends include only low-noise amplifiers and analog delay lines while the rest of the blocks sit in a back-end processer and connects to the front-end through a cable. However, as the number of channels increases, interconnects between the transducer and CMOS chip become the bottleneck. State-of-the-art has demonstrated the technique of flip-chip bonding between the 2D 32x32 Capacitive Micromachined Ultrasonic Transducer (CMUT) array and IC . On the other hand, a single-chip solution for the front-end circuitry of a high-channel count has been shown in recent publication . Therefore, this research focuses on the realization of pitch-matched electronics which enable the integration of front-end circuitry for 2D array and maintain the capability of direct assembly with a CMUT array.
In the proposed architecture, each pixel has a dedicated set of front-end to achieve parallel processing. The on-chip analog-to-digital conversion can improve the signal integrity during the cable transmission but also inevitably increase the complexity of the front-end circuitry. To meet the stringent area requirement, the single-bit sigma-delta beamforming is used to reduce the hardware complexity by moving the delay-lines and adder to digital domain. Moreover, inverter-based amplifier is utilized in the design to further minimize the area. A test chip with 4 by 4 channels has been fabricated in 28nm technology and is under measurement.
 Anshuman Bhuyan, et al., “Integrated Circuits for Volumetric Ultrasound Imaging With 2-D CMUT Arrays” IEEE Trans. Biomed. Circuits Syst. VOL. 7, NO. 6, DEC. 2013
 Ji-Yong Um, et al. “An Analog-Digital-Hybrid Single-Chip RX Beamformer with Non-Uniform Sampling for 2D-CMUT Ultrasound Imaging to Achieve Wide Dynamic Range of Delay and Small Chip Area” ISSCC 2014
Email: manchiac AT stanford DOT edu