AN EXTENDED UTD ANALYSIS FOR RCS COMPUTATIONS INVOLVING HIGHER-ORDER CURVED SURFACES

An extended UTD (EUTD) solution is developed for the scattering and diffraction of high frequency EM fields from higher order (polynomial and spline defined) curved surfaces. The new solution is computationally efficient and overcomes the difficulties of the classic GO/GTD/UTD solutions near ray caustics and caustic terminations. The approach for constructing the EUTD solution is based on a spatial domain radiation integral representation for the scattered field which is then reduced using a uniform asymptotic procedure. Further heuristic modifications are also made and correct the GO induced current assumption near the shadow boundaries. New uniform reflection, first order edge diffraction, and zero-curvature diffraction coefficients are then derived and involve higher order phase integrals as canonical functions. Numerical results involving third and fourth order polynomial strips are provided and compare favorably with reference moment method results.