Adaptive pulselength correction (APLECORR): a strategy for waveform optimization in ultrawideband active sonar

Abstract

This paper describes adaptive pulselength correction (APLECORR), an environmentally adaptive technique for optimizing the detection performance in wide-band active sonars in so-called doubly spread channels. It works by allocating available transmit energy to frequency bands according to the in situ measured reverberation and ambient noise spectra. It optimizes the waveform and the detection processor at the same time. It is appealing in its simplicity and achieves significant gains whenever the reverberation-to-noise ratio is not constant across frequency, thus its applicability to wide-band systems. The method extends easily to PRN and other non-FM waveforms. The paper includes a proof that time spreading and frequency-spreading distortion have an approximately equivalent effect if the waveform is linear or hyperbolic frequency modulation.