Signal Investigation for Low Frequency Active (LFA) Sonar
Trider Scientific Limited Dartmouth, NS Canada
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This report describes the categorization of sonar waveforms that are applicable in multi-static low frequency active LFA sonar systems. Two discriminators are the continuous transmission systems and the pulse type transmission systems. Within the pulse type, the waveforms are further classified as to their Doppler and range resolving capabilities. Some signals are referred to as Doppler sensitive and have good Doppler resolving capabilities and low to medium range resolution, while others are referred to as Doppler insensitive waveforms and possess good range resolving capability but moderate to low Doppler resolving properties. Much of this recent work in waveform design has concentrated on signals with both good Doppler and range resolving abilities and are referred to as composite signals. A catalogue type description of signals applicable in each grouping is presented for both continuous and pulse type systems along with a discussion of the impact these signals can have on the sonar receiver signal processing. In addition, some of the recent receiver algorithm work uncovered as part of this pulse review is also included. While some of the newer signals have not been fully evaluated in at-sea trials, the recommendation is made for more detailed investigations of two of the signals identified.