Application of Fourier transform and wavelet transform in signal de-noising
SI Zhen-zhen · Electronic Design Engineering · 2011
For high frequency signals mixed with high frequency noise,using wavelet to de-noise can avoid the useful signal impairment caused by Fourier transform.For a fixed frequency noise signal,using Fourier transform and low filter to reject the noise.For a mixed high frequency noise signal,it is more effective to use orthogonal wavelet function sym4 to de-noise.It firstly decomposite the signal to the fourth floor,and select the appropriate number for soft threshold by minimax criteria.Finally,it use the threshold number to select effective wavelet coefficients for reconstructing the de-noised signal.Experimental results show that such a noisy signal can lost some useful info by Fourier de-noising,and by using the minimax principle to select wavelet threshold can effectively keep some of the useful signal,especially the high-frequency part.