Waveform design of geometric comb to extract target phase feature

The majority of active sonar systems to detect and classify a target based on the amplitude of the received echo strength or the induced Doppler shift. However, additional classification information is available from the phase shift introduced by some targets as a result of the acoustic boundary conditions. In this paper, waveform design of geometric comb using sub-band correlators is presented for measuring the phase shifts associated with certain stationary and moving targets when insonified by broadband transmissions. With the aim of providing improved range resolution, it maintains the amplitude of the transmission constant to maximize energy efficiency and compatibility with existing nonlinear power amplifiers. And the influences on target echo phase measurement are analyzed from reverberation gain achievable with broadband, Doppler sensitive geometric comb transmissions in littoral waters. At last, field trial results are given for a mine-like classification sonar system and a forward-looking sonar system designed for operation near the sea surface.