Parameter estimation for linear FM signal

A new method is introduced for parameter estimation of linear frequency modulated (LFM) signals, which consists of a coarse search and a fine search. In the initial stage, the window length for short time Fourier transform (STFT) is selected to get the right time-frequency resolution and concentrate the energy to a line in spectrogram according to the LFM signal characteristic, then the line of ridge energy is tracked in the spectrogram, and the parameters of LFM signal can be estimated coarsely. In the second stage, the fine search for correct parameters is implemented in the fractional Fourier transform (FRFT) domain using Gaussian model to fit the impulse response of the LFM signals under the guidance from the above stage by the property of monotonicity in the limited neighborhood of the optimal value. Computer simulations have verified the effectiveness of the new method.