Time-reversal based detection of buried objects in waveguide environments

For improvement of detection of a buried object in shallow water, a robust time reversal detection approach is proposed. Time reversal processing (TRP) is commonly applied for signal enhancement in a homogenous medium. In this paper, time reversal focusing in non-homogenous media is theoretically analyzed based on a wave propagation equation. From the perspective of beamforming, TRP is equivalent to active matched field processing (MFP). It is necessary to consider the robustness of TRP in an uncertain environment. Thus an optimum algorithm with multiple constraints is combined with the TRP scheme for designing time reversal beams to ensonify a target of interest. The tank experimental results verify the theoretical analysis of time reversal focusing in layered media. The proposed time reversal processing scheme works well in detection of a buried object in a waveguide tank. Moreover, by robust time reversal we can achieve a processing gain of 11.8 dB.