Peter G. Cable
BBN Systems and Technol., Union Station, New London, CT 06320-6147
The shallow water channel is considered as a random, time-varying linear filter. The sources of temporal variation of channel properties considered are source and receiver motion and the motion of the surface (that is, wind waves and swell). Using an energy flux description for acoustic propagation, after Smith, Weston, and Brekhovskikh, and employing Smith's theory of coherence in multimode propagation, an explicit formulation of the scattering function for a shallow water channel has been obtained. The scattering function description seems suited to a mid or high frequency (5--20 kHz) description of the shallow water channel. The conditions necessary for the scattering function description, namely that the channel be wide-sense stationary with uncorrelated scatterers (WSSUS), are derived and discussed. Specific examples of the scattering function for different channels will be presented and discussed.