Two dimensional local maximum synchroextracting chirplet transfrom and application of characterizing micro-Doppler signals

Abstract

Methods related to reassignment have attracted great attention in recent years due to their efficiency in improving the readability of classical time-frequency (T-F) representations (e.g. the spectrogram and scalogram). Since most of the reassigning methods require the signal components separated by sufficient frequency distances, they are rarely applied to analyze the micro-Doppler (m-D) signals whose components commonly overlap in the T-F domain. To address this issue, we propose a chirplet transform based reassignment technique that performs the local maximum synchroextracting operation in both frequency and chirp-rate dimensions. The underlying principle is that m-D modes with instantaneous frequencies cross one another are actually separable as long as their chirp-rates are different. Also, the accuracy of the local maximum based reassignment estimator is analyzed with the guarantee of some error bounds. Compared with several cutting-edge techniques, the numerical experiments show that the proposed method is better at characterizing the m-D signals, particularly at the crossover regions in the T-F plane.