Space-time prewhitening method for LFM reverberation based on fractional Fourier transform

A space-time prewhitening method (STPW) based on fractional Fourier transform (FRFT) is presented to solve the high false alarm detection problem of active sonar in shallow sea. This method transforms the reverberation to fractional Fourier domain to whiten using FRFT. The linear varying frequency in linear frequency modulation (LFM) reverberation is transformed to stationary frequency, the local stationarity of reverberation is enhanced, and the prewhitening performance is improved. Finally, experiments with real reverberation data verify that the proposed method improves the detection probability of matched filter detector by 13% averagely in the range of signal-to-reverberation ratio (SRR) -16 dB~0 dB, and the detection performance of active sonar is improved significantly.