Doppler Effect Analysis of Bottom Reverberation for a Moving Platform in Shallow Water

Bottom reverberation is hardly avoided for active sonar working in shallow water waveguide. In this paper, a monostatic reverberation model of a moving narrowband source in shallow water is developed. The power spectrum distribution of the bottom reverberation signal received by a small moving platform is also discussed. For the active option of a moving underwater vehicle, the Doppler shift occurs during such two processes: sound wave incident from the platform to the scatter and scattering back to the platform. Considering the scattering field comes from multiple directions of the seafloor, the received reverberation signal has different levels of frequency shift. To consider the influence of different propagation paths on the reverberation Doppler Effect, both ray theory and ray-mode analogies are introduced for the reverberation model, and the simulation results show that when the moving platform moves at a certain speed, the energy of the received reverberation signal is broadened due to Doppler Effects. Meanwhile, the spectrum peak will also expand from the center frequency to both ends.