A Quadrature Adaptive Coherent Lock-in Chip-Based Sensor for Accurate Photoacoustic Detection

For wearable biomedical devices, it is essential to detect target signals under high noise and strong interferences. Moreover, it is critical to realize the system with compact size and easy implementation. To address both goals, this paper presents a chip-based photoacoustic (PA) sensor called QuACL. By leveraging the adaptive coherent lock-in technique, the high sensitivity and specificity can be achieved for detecting target signals. In-phase and quadrature PA templates are specifically designed based on the profile of the target signal and are generated by the FPGA board and the DAC board. The received signal is correlated with the templates to capture, track, and recover the target PA signal. Fabricated in 65-nm CMOS technology, the chip-based sensor system occupies only 0.6 mm
²
area. The robustness and versatility of the QuACL sensor system are verified by the experiments on discerning and recovering weak PA signals accurately.