LAUSR

Odd harmonic interference is observed in a fast digital lock-in amplifier (FDLIA) with square wave signals as carrier and reference signals, which will reduce spectrum utilization. To address this problem, a method to suppress odd harmonic interference by calculating the phase of one carrier without the same harmonic as other carriers is proposed. Through simulation and multispectral image acquisition experiments, compare the similarity of the signals before and after correction by the proposed method with the original signal. The results show that the structural similarity (SSIM) and the peak signal-to-noise ratio (PNSR) of the signal corrected by the proposed method are significantly improved and the mean square error is significantly decreased, which fully demonstrates that the proposed method can effectively suppress the odd harmonic interference and thus improve the spectrum utilization of the fast phase locking algorithm based on square wave signals. This method will increase the application value of modulation and demodulation methods in multichannel signal detection.