Modelling broadband scatter from periodic sea surfaces

Abstract

Surface waves are the primary source of short time-scale variation of the channel impulse response in underwater transmission scenarios when source and receiver positions are fixed. This study proposes an exact method for modeling the single surface bounce path of the channel impulse response, which contains most of short time-scale effect. This method is designed for one dimensional, periodic wave profiles, and solves the scattering problem as a series of motionless surfaces. To create a time series for each surface, the proposed method solves the Helmholtz equation at many frequencies, performing three steps at each frequency. First, the point source is decomposed into a series of plane waves, each of which scatter from the surface at a finite number of Bragg angles. Second, the amplitudes of these discrete scattered plane waves are found with an exact method. Finally, the surface response for a three-dimensional point source is recovered with a plane wave synthesis of these scattered plane waves. The results of this study are intended as a reference to inform the interpretation of surface scattering results from more common underwater acoustic models.