Measurement algorithm of nonstationary signal based on time and frequency optimization using wavelet packet transform
Cat Lab · Yiqi yibiao xuebao · 2009
Nonstationary signal is one of the most important targets analyzed in measurement field.Classic methods like the Fourier Transform(FT) could not be used effectively in this case.Wavelet Packet Transform(WPT) is one of the useful tools to analyze the nonstationary signals.Shannon wavelet function is the only one that can divide the frequency domain of the signal strictly in single wavelet function family.But the time waveform of Shannon wavelet is not compactly supported,so its application is limited.An algorithm is proposed in this paper,which optimizes the Shannon wavelet function both in time and frequency domains synchronously.Firstly,in time domain,by modifying the time expression of the function,the performance of the time filter is improved;secondly,an interpolation algorithm in frequency domain is proposed to improve the frequency filtering characteristic;then a fast computation implementation of the algorithm is given by applying the Newton iterative algorithm.Finally,numeric simulation is carried out.The result proves that the algorithm can improve the performance of the transform effectively and can be used as one of the powerful nonstationary signal test tools in the measurement system.