Bottom object echo time-frequency processing based on two dimension fractional Fourier transform reassignment spectrogram

Based on reassigned time-frequency distribution theory, and given the practical implementation, the reassigned Wigner-Ville distribution, reassigned short time Fourier transform (STFT) and reassigned fractional Fourier transform (FrFT) distribution characteristics were discussed. The two dimension reassigned FrFT was selected to represent underwater target echo which was contaminated by serious bottom reverberation. Then time-frequency matched detector was designed. The experimental data analysis shows that reassigned FrFT spectrogram was able to represent bottom echoes components' time frequency local characteristics. Two kinds of target echoes energy concentrations were obvious in time frequency plane. The proposed method helps to improve underwater target detection performance.