A perturbation method for transient multipath analysis of electromagnetic scattering from targets above periodic surfaces

A cylindrical target above a simulated sea surface is illuminated by a short-pulse electromagnetic wave to study the effect of multipath on radar measurements of targets above the sea. A new solution technique is outlined in this thesis for both TM and TE scattering from a cylinder above an infinite, periodic surface. A series of time-domain experiments have been performed to verify the theoretical results.;The basis of the new solution technique is that if a target is close to the sea, the current induced on the sea surface will be nearly identical to that induced by a plane wave without the target present, except within a region of finite extent immediately beneath the target. A set of coupled Electric-Field Integral Equations (EFIEs) for the current induced on the cylinder and the perturbation current (the difference between the current with the target present and with the target absent) on the surface has been derived in which the perturbation current is approximated to zero outside a finite region beneath the cylinder. The EFIEs are solved in the frequency domain using the Method of Moments and transformed into the time domain using the inverse Fourier transform. The time domain results are used to investigate the effects of multipath for various sea surface profiles.