The contribution of multipathing effects in ground-wave radar return from the sea surface

Srivastava, Ravi Swarup (1987) The contribution of multipathing effects in ground-wave radar return from the sea surface. Masters thesis, Memorial University of Newfoundland.

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Abstract

The second-order ground wave spectral cross section of the ocean surface given by existing theories corresponds to the case where both theoretical scatterings occur within the bounds of a specific area or patch of the ocean surface. Another additional term in the second-order cross section given by Walsh and Srivastava (1987), which represents the phenomenon where at least one scattering occurs outside the bounds of the patch of the ocean surface, is examined. The properties and significance of this off-patch scatter (a multi-pathing effect) are discussed. -- The off-patch spectral cross section expression is simplified for a narrow beam receiving antenna. By using suitable numerical techniques, a computer program is developed for calculating this cross section. The program is applicable for wide beam transmitting antenna. Theoretical Doppler spectra are generated for different radar frequencies and sea states to study the importance of this type of scatter. A comparison is carried out between the Doppler spectra of the above two kinds of scatter for various sea conditions to infer the effect of off-patch scatter in extraction of ocean surface parameters. Two possible cases, first when the radar is located on the open ocean and second when it is located on the beach, are considered for the comparison. -- It is determined that off-patch scatter is not significant in Doppler regions near the first-order peaks, which are commonly used to extract the ocean surface parameters. However, at some Doppler frequencies its contribution may be important as contending ocean clutter in target detection problems.

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