Weak Signal Detection Circuit Based on Dual-Phase Lock-in Amplification Technology

This paper introduces a novel lock-in amplifier circuit designed for extracting weak sensing signals in noisy environments. The circuit employs two orthogonal vector reference signals, which are multiplied by the measured signal after low-noise amplification and band-pass filtering, to detect signal phase differences effectively. The phase-sensitive detector (PSD) converts the measured AC signal output from the signal channel into DC by phase-sensitive detection. Finally, the weak signal is extracted by low-pass filtering and root mean square calculation. Test results confirm the design's high precision in signal extraction, alongside its simple circuit structure and minimal component consistency requirements, addressing the typical need for predictive alignment in ordinary amplifiers between the measured and reference signals.