Rough surface scatter Doppler measurement by impulse probing

In order to obtain rapid repeatable measurements of the frequency spreading produced by scattering of acoustic signals from a wind‐ronghened surface, a measurement technique has been developed for use in conjunction with a model tank. The technique uses pre‐emphasized impulsive probing signals to sample the scatter channel transfer function at a rate in excess of the Nyquist rate for fading. A large number of measurements at a variety of frequencies, beam patterns, and geometries have been made. These measurements are highly repeatable and precise. They show a variety of phenomena including upward and downward skewing of the Doppler spectrum, harmonics of the surface temporal spectrum, and a generally Gaussian spreading at high Rayleigh parameters. In general they are not in agreement with current predictive theories, but represent an excellent set of reference measurements against which to measure the effectiveness of future theoretical refinements. [Support: ONR (480), Naval Electronic Systems Cmd. (320).]