New sonar waveforms for active torpedo warning using an LFAS system

Low Frequency Active Sonar (LFAS) systems are originally designed for ASW purposes. Although their main purpose is detection of submarines, they can, if adjusted waveforms are transmitted, also be used for detection of small fast moving targets (torpedoes). In this study the Detection, Classification and Localisation performance of classical HFM and CW pulses is compared to that of three new wideband Doppler sensitive pulses. The PTFM (Pulse Train of Frequency Modulated signals) has already proven effective in suppression of reverberation in ASW trials. Two mutants, the DTFM and TTFM (a double train and a triple train) combine this property with high range resolution, at the cost of little lower Doppler resolution. This improves localisation and even allows for hard-kill solutions. Pulse properties of the 5 candidate pulses have been analysed theoretically and experimentally during a sea trial. The first analysis results of this sea trial are compliant with theory