Amplitude characteristics of linear frequency modulation signal in FRFT domain

Parameter estimation of linear frequency modulation signal (LFM) is one of important problems of radar or sonar. Because the fractional Fourier transform (FRFT) can centralize the energy of LFM, FRFT became an important way to estimate the parameters of LFM. The location of the FRFT spectrum´s peak was close relative with the chirp rate and central frequency of LFM. The finer we search the peak in FRFT domain the estimated parameter is more accurate. But the finer search results in the huge computation. In this paper, based on the definition and properties of FRFT, the amplitude characteristics of analytic LFM in FRFT domain was derived. According to those characters, the multi-resolution based-5 point was proposed for increasing the speed of search. It can speed up the search.