Comparative Study and Experimental Validation of Phase-Sensitive-Detection Techniques for Sensor Lock-in Amplifiers

Often in a sensor system, the signal of interest from the sensor is smaller than the signal due to noise. Lock-in amplifiers have been used to efficiently differentiate the signal of interest from noise and unwanted signals in such scenarios. Phase-sensitive detection (PSD) is an important building block of a lock-in amplifier. Analog switches and multipliers are the two most widely used techniques for the phase-sensitive detection of sensor lock-in amplifiers. Each technique has some distinct advantages and disadvantages as well. In this paper, we have studied and experimentally validated the performance of these two techniques for the PSD in sensor lock-in amplifiers. The techniques are validated with a sine wave, square-wave excitation, and modulation signals. Further, the methods are validated by integrating with a lock-in amplifier. Finally, the performance analysis of these two techniques is tabulated based on the obtained experimental results. The results show that the multiplier-based system shows an error of less than 1%, whereas the square-wave excitation system shows an error as high as 5%.