新型锁相放大器的设计

The design of the new lock-in amplifier

锁相放大器是一类利用相关算法检测强噪声背景下微弱信号的先进仪用放大器。但传统锁相放大器在检测微弱信号时需要参考信号和被测信号同频同相,而在实际测量中要求二者同频同相很难,且容易导致运算误差。针对2个频率或相位有差异的信号运算后出现误差的问题,提出了一种基于自相关检测理论的新颖的设计方案,即在参考信号与被测信号频率和相位都不相同时,对2信号进行三次乘法运算最终输出直流电压。实验结果将输出值与理论值进行了比较,二者误差在允许范围内,验证了设计理论的正确性。

The lock-in amplifier is an advanced instrumentation which can detect and amplify weak signals under strong noise background by using related algorithms. However, when traditional lock-in amplifiers detect weak signals, they require reference signals in the circuits have the same frequencies and phases with measured signals. In the measurement, it is difficult to claim the two signals to have the same frequencies and phases and prone to operator errors. In this article, we proposed a novel design scheme based on the theory of self-correlation detection aiming at solving the errors of the two signals＇ operation which have some differences in frequencies and phases. After three multiplications of reference signals and weak signals, the final output is DC voltages. The results of the experiments are compared with theoretical values, the errors between the two is in the scope of the permission. The pictures of the results show that the new theory and circuit are correct.