Influence of Multipath on Some Waveforms for Active Sonar: The Wideband Case(Inverkan av Flervaegsutbredning pa Nagra Vagformer foer Aktiv Sonar: Det Bredbandiga Fallet)

摘要

In this report, the authors study how different types of active sonar signals areaffected by the environmental acoustics in the Baltic Sea. The waveforms studied are PCW (Pulsed Cosine), LFM (Linear Frequency Modulation), HFM (Hyperbolic Frequency Modulation or Linear Period Modulation), BPSK (Binary Phase Shift Keying), and a Costas sequence in the wideband case. The wave forms have been analyzed using the autoambiguity function. The authors have also studied the effect of a weighting function and the influence of multipath using an isovelocity propagation model. The main conclusions of this report are that the PCW signal is not influenced by multipath wave propagation and that the LFM, the BPSK, and the Costas signal are disturbed by a strong range sidelobe. They also conclude that the Costas sequence and the BPSK signal provide good range and velocity resolution for the ideal case. When using Hanning weighted signals with the multipath model, the conclusions are similar to the single path case: only the PCW signal benefits from the weighting.