Electromagnetic Backscattering from Radar Antenna Footprint Confined Infinite Surfaces

This work studies the electromagnetic (EM) backscattering from an infinite surface whose illuminated area is confined by radar antenna footprint, which represents the cases for calculation and measurement of radar clutter from land and sea. We highlight the fact in such cases that the illuminated area depends on the radar antenna footprint, thus always belonging to a near-field problem. The analytical expression for the radar cross section (RCS) of antenna footprint confined infinite plate at normal incidence is derived, with the radar distance-variant characteristics being explained in terms of two interfering scattering centers. Using Kirchhoff approximation (KA) and small perturbation method (SPM), the near-field backscattering from rough sea surfaces is also studied, where both spherical wavefront and antenna pattern tapering are considered. Numerical simulation results demonstrate that radar range and antenna pattern do impact on the calculated RCS and backscattering coefficient for both smooth and rough surfaces.