Non-recurrent wideband continuous active sonar

This paper presents a continuous active sonar (CAS) waveform which enables high revisit rates and wideband processing gains to be achieved with suppression of range-ambiguous returns. Non-recurrent wideband linear FM signals with circular Costas frequency-staggering across chirp repetition intervals is shown to provide ambiguity functions with good Doppler and range resolution, controllable Doppler and range ambiguities, and a high revisit rate. These slow-time Costas or “SLO-CO” CAS waveforms allow for the possibility of updating range-velocity estimates every pulse repetition interval while achieving the clutter suppression associated with the use of conventional wideband LFM signals.