GLRT-based detection in bistatic sonar under strong direct blast with multipath propagation

Direct blast, a strong interference in bistatic sonar, is difficult to suppress because of multipath propagation for blasts and signals. A generalized likelihood ratio test (GLRT)-based detection scheme in the frequency domain of the received signals was proposed, and the unknown parameters were estimated using maximum likelihood estimate (MLE) under a multipath environment. The distributions of the test statistic of detectors for known and unknown noise power were given in theory, and the probability of detection was determined. The performance of the detector decreases by 4 dB when the noise power was evaluated using MLEs. Simulations demonstrated the effectiveness of the detector under active detection configuration with a large bistatic angle under a low signal-to-direct blast ratio (SDR). The impact factors, such as the SDR, bandwidth, path number and DFT point number were discussed. The proposed detection scheme was verified with a lake experiment.