A fractional Fourier transform approach for parametric array sub-bottom profiler signal processing

By modulating a linear frequency modulated (LFM) signal onto a high-frequency carrier and transmitting it through the parametric acoustic array (PAA), the self-demodulation low-frequency signal (SD-LFM) can be generated in the far field, which settles the problem of detection range and high range resolution preferably in application. Compared with traditional signal processing method such as pulse compression, fractional Fourier transform (FrFT) is more suitable for time-frequency analysis of LFM and SD-LFM signals. A FrFT approach for parametric array sub-bottom profiler signal processing is proposed in this paper. First, SD- LFM signal generated by PAA is studied, then optimal fractional Fourier transform is performed to obtain the energy centralized signal in fractional Fourier domain (u domain). After that, u domain windowed filtering is done to filter out the in-band noise and enhance the signal. Finally, time dimensional transformation is used to get the high-quality sub-bottom profile in time domain. The performance of the proposed method is verified by simulations, which indicate the effectiveness of the algorithm.