A Super-Sensitivity Photoacoustic Receiver System-on-Chip Based on Coherent Detection and Tracking

Abstract

Photoacoustic (PA) imaging is becoming more attractive because it can obtain high-resolution and high-contrast images through merging the merits of optical and acoustic imaging. High sensitivity receiver is required in deep in-vivo PA imaging due to detecting weak and noisy ultrasound signal. A novel photoacoustic receiver system-on-chip (SoC) with coherent detection (CD) based on the early-and-late acquisition and tracking is developed and first fabricated. In this system, a weak PA signal with negative signal-to-noise-ratio (SNR) can be clearly extracted when the tracking loop is locked to the input. Consequently, the output SNR of the receiver is significantly improved by about 29.9 dB than input one. For the system, a high dynamic range (DR) and high sensitivity analog front-end (AFE), a multiplier, a noise shaping (NS) successive-approximation (SAR) analog-to-digital convertor (ADC), a digital-to-analog convertor (DAC) and integrated digital circuits for the proposed system are implemented on-chip. Measurement results show that the receiver achieves 0.18 µVrms sensitivity at the depth of 1 cm with 1 mJ/cm ² laser output fluence. The contrast-to-noise (CNR) of the imaging is improved by about 22.2 dB. The area of the receiver is 5.71 mm ² , and the power consumption of each channel is about 28.8 mW with 1.8 V and 1 V power supply on the TSMC 65 nm CMOS process.