From Murmann Mixed-Signal Group

BSEE, Massachusetts Institute of Technology, 2009

MSEE, Massachusetts Institute of Technology, 2010

Admitted to Ph.D. Candidacy: 2010-2011 

Research:  Low Power Integrated Analog Front Ends for Portable Ultrasound Imaging

My research focuses on designing low-power systems for portable medical applications. Specifically, this work focuses on exploiting the signal properties inherent in medical ultrasound imaging to design a more efficient analog front end (AFE) which would be suitable for integration into handheld medical imagers. Ultrasound imaging typically consists of a high dynamic range, wide-bandwidth signal centered around a known transmit frequency. This signal characteristic can be exploited in the data conversion circuitry to create a lower-power solution. Traditional commercial solutions consist of power-intensive pipeline ADC's to capture the full dynamic range of the ultrasound signal directly.  A more energy efficient approach is devised by noting that we can predict bandlimited signals based on past data samples.  This technique allows us to increase the effective dynamic range of a quantizer by allowing a larger input signal than the quantizer could normally resolve.  Given that such a prediction system requires oversampling, the dynamic range can be further improved by implementing noise-shaping on the quantization noise from the predictive quantizer.  A diagram illustrating this technique is shown below, using a low resolution SAR ADC as the predictive quantizer in the top loop, and a first-order discrete-time sigma delta loop to shape the quantization noise left on the SAR sampling capacitors at the end of the conversion cycle.

Email: jspauld AT stanford DOT edu