Detection of broadband signals in frequency and time dispersive channels

A major problem for active sonar systems operating in shallow water is reverberation. High time-bandwidth waveforms and coherent matched filtering are often used to improve detection performance in reverberation. However, an active sonar echo undergoes distortion during the two-way propagation and reflection from the target. As a result, the full performance gain is not achievable, and this approach is severely limited. In this case, more robust detectors are needed. We evaluate the detection performance of several commonly used detectors in an ideal nondistorting channel, a fast-fading distortion (FFD) channel, and a channel with time-spreading distortion (TSD). We examine the robustness of the various detectors by evaluating the performance in the case of mismatch between the detector and the channel parameters. Studying the relation between the FFD model and the TSD, we show that, under certain conditions, the TSD and FFD channels have an equivalent effect on the waveform.