Bionic-Pulse Fractional Fourier Transform Domain Echo Enhancement Detection Method for Undersea Targets

Sonar detection of small undersea targets remains challenging owing to the weak target echo and substantial seabed reverberation interference. Dolphins possess a sophisticated biological sonar system that is superior to advanced sonars for detecting and identifying targets in complex environments. Based on the dolphin’s bionic pulse for echolocation, a novel method for enhancing echo detection in the bionic-pulse fractional Fourier transform (FrFT) domain is proposed to reduce reverberation interference when detecting undersea targets. First, the bionic detection signal parameter is designed, and the optimal-order FrFT spectrum is derived. Then, based on the characteristics of the bionic bipolar signal’s FrFT spectrum, a FrFT point spread function (PSF) is generated to enhance the target echo and suppress reverberation interference. Combined with the bipolar bionic-pulse sonar processing algorithm in the FrFT domain, this approach shows improved undersea-target detection performance. Finally, the experimental results show that the output signal-to-reverberation ratio (SRR) of a target achieved using the proposed method is >9 and 6 dB higher than those achieved using the twin inverted pulse sonar and space-time combined high-resolution processing (STCHP) methods, respectively, irrespective of high-frequency or low-frequency twin inverted pulse signal utilization. Therefore, the experimental results demonstrate the effectiveness and high accuracy of the proposed method.