Accession Number : AD0709453

Title :   SCATTERING OF MICROWAVE RADIATION FROM A TURBULENT WATER SURFACE,

Corporate Author : CALIFORNIA UNIV BERKELEY ELECTRONICS RESEARCH LAB

Personal Author(s) : Tremain,D. E. ; Angelakos,D. J.

Report Date : 01 JUL 1970

Pagination or Media Count : 62

Abstract : An experiment has been constructed to investigate the feasibility of detecting low frequency underwater sound sources under turbulent surface conditions by illuminating a small portion of the water surface with an unmodulated beam of 8mm microwave radiation. The unmodulated beam became phase modulated upon reflection from the water surface. This phase modulation was detected by a synchronous phase detector and was processed using digital autocorrelation and Fast Fourier Transform techniques to yield the spectral components present in the water surface. The angular positions of the transmitting and receiving antennas with respect to the surface normal were adjustable independently over wide ranges in this experiment. Results have been obtained for the case of specular reflection in which the angles of incidence and reflection each varied from 5 degrees to 50 degrees, with respect to the surface normal. These results indicate that a submerged source vibrating with a large amplitude at a frequency above the surface roughness spectrum may be detected readily for angles of incidence and reflection up to about 35 degrees from the normal. The source may be detected for angles of incidence and reflection between 40 degrees and 50 degrees only if two or three transforms are averaged; detection is more difficult for angles in this range. A number of cases of backscattering have been investigated as well, but the source could not be detected in any of these cases because the detection system was not sufficiently sensitive. (Author)

Descriptors :   (*UNDERWATER SOUND SIGNALS, DETECTION), (*RADIO WAVES, SCATTERING), LOW FREQUENCY, OCEAN WAVES, SURFACE ROUGHNESS, BACKSCATTERING, INTEGRAL TRANSFORMS, STATISTICAL FUNCTIONS, COMPUTER PROGRAMS, FEASIBILITY STUDIES

Subject Categories : Acoustics
      Radiofrequency Wave Propagation

Distribution Statement : APPROVED FOR PUBLIC RELEASE