Advisor: Bruce Wooley

Research Summary

Real-time three-dimensional (3-D) ultrasound imaging for medical and underwater applications is an area of expanding research interest. The realization of real-time 3-D volumetric ultrasound imaging is based on the use of phased two-dimensional transducer arrays with individually addressable elements, together with signal-conditioning, control and high-speed data acquisition circuitry. The integration of the ultrasound transducer array with supporting electronics offers several advantages, such as, improved sensitivity, lower crosstalk, reduced power dissipation and, a compact design to expand the space of possible applications. Capacitive micromachined ultrasonic transducers (CMUTs) offer a practical means of implementing these transducer arrays because they can be implemented in silicon integrated circuit technology while providing both wide bandwidth and high sensitivity, as well as the potential for integration with supporting circuitry.

The implementation of the analog-to-digital (A/D) conversion as an integral part of the system electronics decreases the sensitivity of the system to analog circuit imperfections and eliminates the need for an unmanageable number of interconnects between the ultrasonic transducer array and the processing unit. On the other hand, high-quality ultrasound imaging requires increased signal bandwidth and conversion resolution, thus increasing the A/D interface complexity, cost, and power dissipation. The diverse requirements encountered in some applications, such as a large number of array elements for high quality imaging and compact design for portability, further complicate the design and realization of the A/D interface. For example, the area and power constraints become especially severe for ultrasound probes designed to fit in an endoscope.

The goal of this research is to explore how multiplexing and pipelining can be employed to reduce the cost and hardware complexity of a medium-to-high resolution A/D interface for wideband multichannel applications. A novel architecture is demonstrated for the implementation of a multichannel pipeline A/D converter for use in a real-time integrated 3-D ultrasound imaging probe. An experimental prototype of the proposed A/D interface, integrated in a digital CMOS technology, is capable of digitizing eight parallel channels, each with an effective signal bandwidth as wide as 10 MHz, with 10 bits of resolution. The prototype circuit occupies less than 4 mm² of active silicon area and dissipates a total of 330 mW from a 2.5-V supply.

Education

• Ph.D., Candidate in Electrical Engineering, Stanford University
• M.S., Electrical Engineering, Stanford University, 1998
• B.S., Electrical Engineering, Sharif University of Technology, 1994

Publications

"A multichannel, pipeline analog-to-digital converter for an integrated 3D ultrasound imaging system," in Proc. of  ESSCIRC'02, pp. 263-266.

 

"Capacitive micromachined ultrasonic transducers: Next-Generation arrays for acoustic imaging?," IEEE Trans. Ultrason., Ferroelect., Freq. Contr., vol. 49, pp. 1596-1610, Nov. 2002.

"Initial pulse-echo imaging results with one-dimensional capacitive micromachined ultrasonic transducer arrays," in Proc. of IEEE Ultrason. Sympos., pp. 959-962, Oct. 2000.

 

"Two-path bandpass sigma delta modulator with extended noise shaping," in ISSCCDig. Tech. Papers, vol. 43, pp. 222-223, Feb. 2000.

Contact Information

Phone: (650) 723-3946
Fax: (650) 725-6278
E-mail: kambiz@stanford.edu

Integrated Circuits Lab

Center for Integrated Systems

Stanford University