The application of short time fractional Fourier transform in processing underwater multi-frequency LFM signal

LFM signal is used in underwater signal processing commonly. When there are multi-number objects, the received signal always is multi-frequency LFM signal. Based on short-time Fourier transform and fractional Fourier transform, the short-time fractional Fourier transform is used to process the multi-frequency LFM signal. For the arbitrary LFM signal component, it can get a impulse function in the fractional domain, when choosing the relevant rotation angle. As for other components, the energy is concentrated in a range of frequency at this rotation angle. Therefore, the short-time fractional Fourier transform has best energy collection for the LFM signal. The simulation and test result show that the short-time fractional Fourier transform is valid when processing the multi-frequency LFM signal.