Stochastic model of hydroacoustic signals received on an antenna in the mode of noise direction finding in a shallow sea

Abstract

Knowledge of a mathematical model of hydroacoustic signals, received on an antenna operating in the mode of noise direction finding in a shallow sea, is necessary when solving the problem of synthesis of algorithms for spatio-temporal signal processing, the purpose of which is to solve the problem of primary detection, resolution and estimation of parameters of marine objects. The expected signal, which we also call a wave packet — is the sound pressure field on the antenna receivers created by the natural noise emission of a marine object. The article discusses issues related to problems with the use of existing signal models described using the waveguide eigenfunctions. The main problems: the difficulty of obtaining information about the parameters of the waveguide (soil composition, bottom relief, sound velocity profile, etc.); random changes in the parameters of the waveguide due to various irregularitys. An approach to the development of signal models, which takes into account information only about frequency-dependent attenuation coefficients and phase velocities of modes (normal waves) was proposed. A marine object emits white noise was used. An amplitudes and initial phases of the modes are equiprobably, and the phase velocities fluctuate according to the Gaussian distribution was assumed. A stochastic model of the space-time pressure field of the expected signal has been developed and verified. The wave packet should be considered as a Gaussian random process was established. The developed stochastic model is suitable for use in any mutual arrangement of a marine object and an antenna (near or far zone), takes into account inter-mode interactions (beats) due to the antenna resolution, and takes into account fluctuations in the phase velocities of modes. The obtained results with known solutions were correlated.