CMOS Ultrasonic Receiver With On-Chip Analog-to-Digital Front End for High-Resolution Ultrasound Imaging Systems

CMOS capacitive micromachined ultrasonic transducer (CMUT) with integrated front-end circuits for portable high resolution ultrasonic imaging systems is presented. The CMUT array operates with 30 V power supply. In addition, the interlayer metal CMUTs with non-uniform membrane are proposed to improve the sensitivity in this paper. A prototype chip containing 48 elements as 12 channels is implemented. The conversion efficiency of the proposed CMUTs is 5.84 times higher than that in the published literatures. The maximum ultrasonic signal bandwidth is 4.5 MHz. CMUT array and the transimpedance amplifiers are integrated on the same chip. In addition, a multibit continuous-time $\Delta \Sigma $ modulator was designed and fabricated in another chip using 0.18-$\mu \text{m}$ standard CMOS process. The chips size are 1.84 and 0.177 mm
²
, and the total power consumption in the receiving mode is approximately 3.01 mW with 1.8 V power supply.