Weak Pressure Signal Detection System Based on Amplitude Modulation Communication

A weak signal detection circuit based on AC modulation is designed to address issues such as zero drift and low-frequency noise interference in DC amplification circuits. The system employs the AD630 phase-sensitive detection circuit as its core, along with amplification and filtering circuits, signal generation circuits, and sensitive components. By utilizing AC modulation technique, the DC signal is converted into an AC signal, eliminating the zero drift issue in the DC amplification circuit and suppressing low-frequency interference to improve system accuracy. The circuit adopts cross-correlation detection method, leveraging the uncorrelated nature of noise and reference signals to enhance anti-interference capability, ensuring that the circuit output voltage is zero when the sensor has zero input. Experimental results demonstrate that the adoption of modulation-demodulation technique can improve circuit accuracy by 3.74 times compared to the original DC amplification circuit. The AC amplification circuit exhibits significantly superior anti-interference performance over the DC amplification circuit, enabling the extraction of the tested signal with an amplitude smaller than 30mV in the presence of 1V noise, with an error of only 0.408%.