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%.

I. Introduction

With the rapid advancement of electronic technology, weak signal detection techniques have been widely applied in various fields such as communication, healthcare, and industry. In weak signal detection, the measured signal is often submerged in a noisy environment due to its low amplitude and wide frequency range. Therefore, amplification and filtering of the measured signal are necessary before acquisition^[1]. However, traditional DC amplification circuits are prone to 1/f noise (low-frequency noise), temperature drift, offset voltage, and other factors, limiting the sensitivity and accuracy of the circuit^[2–3]. Therefore, the design of a highly sensitive and interference-resistant weak signal detection circuit is crucial.