Higher Order Equivalent Edge Currents for Fringe Wave Radar Scattering by Perfectly Conducting Polygonal Plates

-Two sets of higher order equivalent edge currents are introduced which, in combination, account for the first-, the second-, and part of the third-order edge diffraction caused by the fringe wave surface current induced on a perfectly conducting polygonal plate in a radar scattering configuration. The first set represents the fringe wave surface current excited by the incident plane wave at the leading edge on a finite incremental strip extending from the leading edge to the trailing edge. The second set represents the fringe wave surface current excited at the trailing edge by the incident leading edge fringe wave surface current on a finite incremental strip extending from the trailing edge to the third edge. The fringe wave surface current on the plate is approximated by the fringe wave surface current on half-planes appropriately conforming to the leading and trailing edges of the plate. For the second set of higher order equivalent edge currents, this requires a new model for the trailing edge fringe wave surface current. The proposed model will ensure that the normal component a t the trailing edge of the approximate fringe wave surface current represented by the equivalent edge currents is zero. Both sets of higher order equivalent edge currents are defined to be placed at the leading edge, and since they contain very few singularities, these are numerically well behaved. Numerical results for the bistatic radar cross section of a square plate show that significant improvements over a first-order approach are obtained from the use of the proposed higher order equivalent edge currents.