Single-chip mixer-based subarray beamformer for sub-Nyquist sampling in ultrasound imaging

Abstract

Compressed sensing (CS) has been proposed as a method of breaking the seemingly inherent tradeoff between sampling rate and resolution in a variety of applications, such as ultrasound imaging. Although various studies have demonstrated the effectiveness of using CS for sub-Nyquist sampling in ultrasound imaging, a dedicated integrated circuit (IC) has not yet been presented. This work introduces a single-chip mixer-based subarray beamformer, an important component for sub-Nyquist sampling in a CS ultrasound imaging system. The beamformer chip, which performs mixing, filtering, and summation of delayed signals within a subarray, is implemented using a single operational transconductance amplifier. We evaluated the performance of the proposed mixer-based subarray beamformer circuit fabricated using a 65 nm CMOS process with 0.4 mW ch-1 power consumption from a 1.2 V supply. Measurement results indicate that the prototype chip is suitable for subarray beamforming with a 5 ns resolution digital mixing sequence. The IC presented here is the first known implementation of a mixer-based subarray beamformer for sub-Nyquist sampling in ultrasonic applications and is expected to reduce sampling data requirements by a factor of 32.