Moving Target Detection Based on Time Reversal in a Multipath Environment

Abstract

Time reversal can resolve multipath problems and increase the detection probability, but the detection performance decreases when the target is moving. Because of the change in the channel response due to target motion, the focusing effect of a time-reversal-transmitted signal is reduced. In this article, a novel method based on time reversal, which detects a moving target embedded in a multipath environment with channel variation, is proposed. We establish conventional and time-reversal signal models of a moving target in an indoor diffuse multipath environment and derive likelihood ratio tests under these two conditions. The channel parameters and the changes due to target motion are obtained by echo estimation and are exploited as useful information by the detectors. The channel changes are taken into account in the time-reversal detector to improve its robustness. The time-reversal detector proposed in this article possesses the constant-false-alarm-rate property with respect to the unknown background noise. Although Monte Carlo simulation analysis has illustrated the superior performance of both conventional and time-reversal detectors and proved that both methods can improve the detection probability by exploiting the multipath effect, the time-reversal method outperforms the conventional method due to the spatial and temporal focusing effect on the channel.