Adaptive transmit waveform design for active cognitive sonar using multi-tone sinusoidal frequency modulation

Abstract

Cognitive sonar systems leverage information gathered from earlier sensing interactions with the acoustic environment to adapt its system parameters for optimal performance. Of the many system parameters, an active cognitive sonar system could adapt, the acoustic signal projected into the medium, also known as the transmit waveform, has a profound impact on system performance as many of the physical characteristics of the acoustic environment are contained in the return echo signal. This research examines utilizing multi-tone sinusoidal frequency modulated (MTSFM) waveforms as an adaptive transmit waveform model for use in active cognitive sonar systems. The MTSFM waveform’s frequency and phase modulation functions are composed of a finite set of weighted sinusoidal harmonics. The weights for each harmonic are utilized as a discrete set of design coefficients. Adjusting these coefficients results in constant amplitude, spectrally compact FM waveforms that possess a wide variety of performance characteristics, which in the past required a diverse set of waveform types to achieve. The adaptability of the MTSFM waveform model enables a cognitive sonar system to generate waveforms that are finely tuned for the novel scenarios and environments that it may encounter.