On detecting linear frequency modulated waveforms in dispersive channels: alternatives to segmented replica correlation

The paper addresses the problem of detecting echos from linear frequency modulated (LFM) active sonar transmissions when the propagation channel exhibits time spreading distortion (TSD) and fast fading distortion (FFD). Both distortion mechanisms reduce the performance of “high resolution” LFM replica correlators which are designed to improve detection performance in reverberation. Robust detectors are required in this situation. The paper compares two robust detectors: the segmented replica correlator (SRC) and the replica correlator followed by incoherent integration (RCI). The author shows that for LFM, (1) TSD and FFD have an equivalent effect on the signal, (2) the RCI and SRC have equivalent reverberation only output statistics, and (3) the RCI and SRC have equivalent performance against either TSD or FFD. The author points out that while virtually all robust active sonar detectors use the SRC, the RCI is preferable when the amount of distortion is not known apriori