Li Miao, Sun Yue, Liang Zhen, Zhang Shengzhao
School of Biomedical Engineering, Anhui Medical University, Hefei, 230032, China.
Heliyon. 2023 Jan 12;9(1):e12933. doi: 10.1016/j.heliyon.2023.e12933. eCollection 2023 Jan.
Digital lock-in detection technique is commonly used to measure the amplitude and phase of a selected frequency signal. The technique which uses a square wave as the reference signal has an advantage of easier implementation and higher computational efficiency compared to that uses a sine wave. However, one constraint for a square wave reference digital lock-in is that the sampling rate must be the integral multiple of 4 of all the signal frequencies. As the sampling clock may not always be able to set to the integral multiple of 4 of the signal frequencies, the constraint brings inconvenient for the implementation. Presented in this paper is a novel algorithm for square wave digital lock-in detection in which the sampling frequency doesn't have to meet the constraint. The algorithm allows frequency sweep measurements with a fixed sampling rate. For different relationships between the sampling rate and the signal frequency, different calculation equations are provided in this paper. Simulations and actual experiments show the feasibility of the proposed algorithm.
数字锁相检测技术通常用于测量选定频率信号的幅度和相位。与使用正弦波作为参考信号的技术相比，使用方波作为参考信号的技术具有实现更容易、计算效率更高的优点。然而，方波参考数字锁相的一个限制是采样率必须是所有信号频率的4的整数倍。由于采样时钟可能并不总是能够设置为信号频率的4的整数倍，这一限制给实现带来了不便。本文提出了一种新颖的方波数字锁相检测算法，该算法中采样频率不必满足该限制。该算法允许以固定采样率进行频率扫描测量。针对采样率与信号频率之间的不同关系，本文给出了不同的计算公式。仿真和实际实验表明了该算法的可行性。
