Feature extraction of GPS sequence based by single sub-band reconstruction of wavelet packet
Qu Guo · Progress in geophysics · 2009
Environments of GPS observation are becoming more complex.Dynamic measurements include more impact factors.Relations of functions are complicated.They influence the extraction of feature information and the ability of explanation of parameter models.Wavelet packet has an advanced time-frequency analysis capabilty.During the progress of decomposition and reconstruction of GPS data sequence,there are three basic operations,that are convolution,downsampling of keeping one sample out of two,and upsampling of putting on zero between each sample,and these operations produce frequency aliasing such as frequency folding and frequency interleaving .In order to eliminate the aliasing,at each step of decomposition or reconstruction,fast Fourier transform is performed the result obtained by convolving the input signal with filters,setting frequency spectrum of the redunctant frequency components to be zero,and inversely fast Fourier transforms the result after zeroing.The result after processing is the input signal of next step,and single sub-band reconstruction is implemented to extract the feature item of GPS data sequence.The availability of this algorithm is proved by a test example.