Instantaneous Frequency Estimation Algorithm of Non-linear Frequency Modulation Signal in Low SNR Based on Generalized S-transform

Abstract The Nonlinear Frequency Modulation (NLFM) signals have been gradually used in new radar systems, however its instantaneous frequency (IF) estimation is still a difficult problem. This paper introduces the generalized S-transform to NLFM signals processing fields and proposes a new IF estimation algorithm of NLFM signals in low SNR based on generalized S-transform. Firstly, the timefrequency distribution (TFD) of NLFM signals in low SNR is got by generalized S-transform. Secondly, a time-frequency (TF) filtering processing is executed to the TFD of NLFM signals and the noise is restrained. Finally the TFD spectrum ridges are extracted as IF curves estimation from the filtered TFD of NLFM signals. Simulation results demonstrate that the IF estimation algorithm proposed in this paper has better performances in IF estimating of NLFM signal in low SNR than other existing algorithms.