Second-Order Electromagnetic and Hydrodynamic Effects in High-Frequency Radio-Wave Scattering from the Sea
Abstract
A theoretical analysis of high-frequency radio-wave scattering from the sea establishes relationships between the doppler continuum of observed radar echoes and the heights and propagation directions of ocean-surface waves. This provides new techniques for the remote sensing of sea-surface conditions by either monostatic or bistatic radars. Integral expressions for the incremental surface radar cross section per unit frequency are derived, assuming a slightly rough time-varying random surface for the sea. These expressions are a function of surface-height directional spectra and contain electromagnetic and hydrodynamic effects to second order. First-order terms confirm that Bragg scattering from wave trains of a single frequency and direction is responsible for the discrete lines in observed doppler spectra; the second-order terms, which provide a continuum, are interpreted physically by a double Bragg- scattering process that involves an intermediate-scattered radio wave that may be either freely propagating or evanescent. A coordinate transformation provides paths of integration that can be related to specific features in observed doppler spectra and also results in a numerically efficient method for the evaluation of the second-order radar cross sections.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1975
- Accession Number
- ADA087051
Entities
People
- Donald L. Johnstone
Organizations
- Stanford University