Research on Automatic Calibration for Initialization of Lock-in Amplifier

锁相放大器是一种用于解调近场信号的仪器，由于前端模拟链路本身的硬件特性会对待测信号的结果产生影响。本文提出了一种数字锁相启动上位机时初始化校准的方法，目的在于保证前端模拟链路处于最佳的工作状态。矫正电压偏置；最大限度补偿模拟链路引入的增益误差以及DDS输出信号与ADC采样过程中不同步引入的相位偏移。测试结果表明，该方案可实现对上述误差的补偿，显著提高了锁相放大器解调近场信号时的精确性和稳定性。The lock-in amplifier is an instrument used to demodulate near-field signals. Due to the hardware characteristics of the frontend analog circuitry, it can affect the results of the signal under test. This paper proposes a method for initialization calibration when starting up the digital lock-in amplifier’s host computer, aiming to ensure that the frontend analog circuitry operates in an optimal state. It calibrates the voltage offset, maximizes the compensation for gain errors introduced by the analog circuitry, and phase shifts introduced by the asynchrony between the DDS output signal and the ADC sampling process. Test results show that this scheme can compensate for the aforementioned errors, significantly improving the accuracy and stability of the lock-in amplifier when demodulating near-field signals.