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为提高数字锁相放大器的最大调制频率,并同时快速检测双频复合信号,提出一种基于方波参考的快速数字锁相算法。该算法设置四路参考信号,其中两路为频率为f的正交参考信号,两路为频率为2f的正交参考信号。设置两个调制频率分别为(2a-1)f和(4b-2)f,同时对平均滤波器的长度进行设置,避免通道之间产生干扰。试验表明,该算法能同时检测双频复合信号中每个分量的幅值和相位,且幅值误差小于0.7%,相位误差小于0.5%。相敏检波过程中的乘法运算被加法和减法替代,提高数字锁相算法的运算速度,有效扩大锁相放大器的检测带宽。
In order to increase the maximum modulation frequency of digital lock-in amplifier and detect the dual-frequency composite signal rapidly at the same time, a fast digital phase-locked algorithm based on square wave reference is proposed. The algorithm sets four reference signals, of which two are orthogonal reference signals with frequency f and two are orthogonal reference signals with frequency 2f. Set the two modulation frequencies to (2a-1) f and (4b-2) f, respectively, and set the average filter length to avoid interference between channels. Experimental results show that this algorithm can detect the amplitude and phase of each component in the dual-frequency composite signal at the same time, and the amplitude error is less than 0.7% and the phase error is less than 0.5%. Phase sensitive phase detection process multiplication is added and subtracted to replace the digital phase-locked algorithm to improve the operation speed, effectively expanding the detection bandwidth of the lock-in amplifier.