A Comparison of the Recursive and FFT-based Reassignment Methods in Micro-Doppler Analysis

A brief comparison of two time-frequency (TF) reassignment methods is provided in this paper. The main advantage of the considered approach is that it allows energy concentration of the signal distribution on the TF plane to be obtained. Both techniques use the short-time Fourier transform (STFT), however, they can be formulated and computed differently. The first classical method is based on the fast Fourier transform (FFT), while the second one uses a recursive filter bank which, in turn, can be more efficient due to a lower time delay and a reduced computational complexity. Thanks to the proposed methodology, a real-time computation of the spectrogram and the reassigned spectrogram can be obtained. Hence, the reassignment method allows an almost ideal localization of the micro-Doppler signature components in a TF distribution to be obtained. Both approaches are presented, investigated, and validated using real-life radar signals in the form of micro-Doppler signatures originating from different targets.