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 with increasing amount of data acquisition. In order to deal with the resultant raised complexity in 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 with the rest of the blocks sitting in a back-end processer connected by a cable. However, as the number of channels increases, interconnects between the transducer and CMOS chip become the bottleneck. Therefore, this research focuses on the realization of pitch-matched electronics which connect to the transducer array through flip-chip bonding.
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 applied to reduce the hardware complexity by moving the delay-lines and adder to digital domain. Moreover, inverter-based amplifier is heavily utilized in the VGA and the single-bit sigma-delta modulator to further minimize the area. Unlike conventional ultrasound solutions which design for the best, we perform simulations to understand how circuit non-idealities, e.g. distortion, noise, affect the ultrasound images. In this way, we can avoid unnecessary over-design and use the pixel area efficiently.
We will tape out a test chip capable of processing the signal from a 4 by 4 Capacitive Micromachined Ultrasonic Transducer (CMUT) array in parallel. The IC will be fabricated in 28nm technology.
Email: manchiac AT stanford DOT edu