An Improved Noise Filtering Approach for Multi-frequency Phase Sensitive Demodulation

As a key role in multi-frequency signal processing, multi-frequency phase sensitive demodulation (PSD) can be used in communication, sonar, bio-impedance measurement, mutual induction based non-destructive test,etc. Actually, the PSD is a matched filter to the reference signal; and in the presence of Gaussian noise, it can also be regarded as an optimal linear filter. However, in a practical measurement system, the noise often possesses impulsive characteristics,i.e. impulsive noise. Thus, how to effectively reduce the impulsive noise is a challenging research task. This paper introduces a method for the impulsive noise reduction in multi-frequency PSD. It takes full advantage of the signal period and the well-known de-noising features of the median filter (MF). Both simulation and experiment validate the proposed method in reducing the effects of impulsive noise for multi-frequency PSD. The results also demonstrated that the proposed method can achieve higher SNR and better robust.