Analysis of linearity and correlation of acoustic spread spectrum signal in multipath reverberation channel

To analyze the correlation and linearity of acoustic spread spectrum signals in shallow water multipath channels, a virtual source calculation model for Pekeris waveguides in shallow waters with frequency attenuation and seabed loss was established. Pulse signals and spread spectrum signals in shallow seas were simulated, and the linearity of spread spectrum signals in a multipath reverberation environment was preliminarily investigated through experiments conducted in a reverberation chamber. Simulation results show that the frequency domain solution of the virtual source method is consistent with that of the normal mode method, and the same low-frequency mode dispersion phenomenon as the normal mode method can be obtained through the virtual source method, verifying that the virtual source method is suitable for low-frequency problems in ideal shallow water waveguides and Pekeris waveguides; when modal dispersion occurs, the correlation performance of low-frequency spread spectrum signals is better than that of high-frequency signals under the same conditions. Experimental results show that when the time-domain waveform of a low-frequency pulse is distorted and broadened, the spread spectrum signal of the same frequency can accurately measure the geometric delay of the reflected signal, demonstrating that the low-frequency multipath effect can still be regarded as the linear superposition of all "path" signals.