4pUW13. A numerical study of time-domain backscattering from one-dimensional, rigid, random surfaces.

Session: Thursday Afternoon, December 5

Time: 4:27

Author: Vincent Lupien
Location: Dept. of Ocean Eng., MIT, Cambridge, MA 02139


In certain high-resolution target detection systems, impulsive scatter from ocean boundaries gives rise to sonar clutter. In this work, the main objective was to identify the stochastic characteristics of rigid, one-dimensional rough surfaces which create backscatter containing spikes in the time domain. The interarrival time and amplitude statistics of impulsive events were determined numerically through Monte Carlo realizations of different surface types. For each surface the far-field impulse response in backscatter was determined using an exact integral equation method adapted from E. I. Thorsos [J. Acoust. Soc. Am. 83, 78 (1988)]. The impulse responses were convolved with the source spectrum to generate exact backscattered waveforms. Three sets of surfaces were investigated. In the first set, surfaces with a Gaussian correlation function were considered, which possess a single horizontal and vertical scale. In the second set, surfaces with a multiscale, power-law spectral density were investigated. The third set consisted of surfaces made up of adjacent straight line segments, or facets. The co-ordinates of the vertices of each facet were randomized through a discrete stochastic process. The results have provided insight into the physical mechanisms which generate spikes in the time domain and helped distinguish the contribution that localized scatterers make versus those that result from random interference of nonadjacent points on the surface. [Work sponsored by the Office of Naval Research.]

ASA 132nd meeting - Hawaii, December 1996