In ultrasound imaging systems, a charge-sharing successive-approximation-register (SAR) ADC has benefits over a charge-redistribution SAR because the charge-sharing SAR is organically compatible with the subarray beamformer which is deployed to reduce the large channel count. Besides, the noise-shaping (NS) SAR is a promising candidate for developing an ADC with high resolution and power efficiency for the next generation of ultrasound imaging systems. However, most of the published NS SARs are based on charge-redistribution SARs.

This thesis presents a hybrid beamforming zero-crossing-based (ZCB) NS SAR for ultrasound imaging. By reusing the zero-crossing-based circuitry in a hybrid SAR/single-slope (SS) ADC to build up a second-order error-feedback (EF) loop filter, a multi-stage noise-shaping (MASH) 2-0 architecture is formed. Thereby, the noise-shaping characteristic is successfully integrated into a beamforming charge-sharing SAR.

The hybrid beamforming ZCB NS SAR is implemented by 180 nm BCD technology. The ADC achieves an SNDR of 72.9 dB within the bandwidth of interest ranging from 3 MHz to 5 MHz. The power consumption per channel is 1.42 mW at the sampling rate of 24 MHz. The ADC achieves a Schreier figure-of merit (FOMs) of 164.39 dB which is comparable with the prior work using the same technology node. The estimated area of the ADC core including 2 channels is 0.156 mm².