THEORETICAL AND EMPIRICAL RESULTS ON THE CHARACTERIZATION OF UNDERSEA ACOUSTIC CHANNELS
LITTON SYSTEMS INC WALTHAM MA
Pagination or Media Count:
An undersea acoustic link between two points in space is represented as a random time-varying linear filter. It can therefore be characterized by its impulse response, or alternately by various Fourier transforms, known as the transfer functions, spreading function, and bi-frequency function. All four of these descriptors are random functions of two variables. A generalization of the uncorrelated scattering model is proferred and it is shown how it can fit known ocean characteristics. Results are presented of some measurements made of the time and frequency spreading imposed on audio frequency transmissions over open ocean underwater paths. Most of the results deal with frequency spreading there are fine grain time domain measurements. Results are given for several center frequencies ranging from the low hundreds to the low thousands of cycles per second. Paths between both fixed and mobile end points have been measured. The path lengths used have ranged from one-half to several hundreds of miles. The results indicate that many of the simplifying assumptions usually made in discussions of time varying channels are not satisfied by these paths, and these points where the assumptions must be generalized are briefly discussed.
- Non-Radio Communications