Bat echolocation signal processing based on Fractional Fourier Transform

Most bats emit echolocation signal with both constant frequency (CF) and linear frequency modulated (LFM) component in a single pulse. The CF part was used to get crude velocity information, and then the Doppler frequency shift can be used to compensate the LFM signal processing unit which was used to get fine information of the targets. In this article, a compensated fractional Fourier transform (FRFT) was proposed to process the LFM part of the echolocation signal. The main concepts of this method is to use the Doppler frequency shift to adjust the order of the FRFT to match the LFM echo, and then optimal energy concentration can be achieved to get fine information of the targets with high resolution. This method was included in processing the batspsila echolocation signal containing several harmonics. Simulation result implies that compensated arithmetic can get better performance in low signal to noise ratio (SNR) condition and the echolocation resolution is also further improved.