Doppler parameters estimation by Short Time Chirp Fourier Transform

In passive sonar applications, various parameters of the underwater moving targets are often estimated using Doppler shift processing techniques. However, since the targets are usually moving slowly and the spectrum lines of underwater target radiated noise are usually in the low frequency range, the Doppler shift is very tiny. We propose a Short-Time Chirp Fourier Transform method to estimate tiny Doppler shift using a longer time window to solve this problem. For estimation of Doppler parameters, two time-frequency curves are constructed by different time windows of Short-Time Chirp Transform. The intersection point of these two curves can be used to estimate the time of zeros Doppler and Doppler centre frequency exactly. The estimation errors of the proposed method are always less than the steplength of slipping window. Therefore the error of estimation can be controlled within the desired range. Simulation results are presented to demonstrate the feasibility of the proposed method.