Residue-series computation of lit-region fields via a novel function P*(/spl xi/,q,u)

Summary form only given. While in the case of a smooth perfectly-conducting scatterer, transition-region electromagnetic fields can readily be obtained from tabulated values of familiar integrals, such tabulated values are not, in general, available in the case of an impedance or coated scatterer. A comparison between the solution of Hussar and Albus (1991) with the more familiar UTD shadow-region solution of Pathak, Burnside and Marhefka (1980) for a conducting scatterer, and for impedance and coated cylinders proposed by Kim and Wang (1989) suggests the introduction of a novel function p*(/spl xi/,q,u) with the property that p*(/spl xi/,q) (a Pekeris function) is rapidly approached as u increases past unity. Extension of this function into the lit region is easily achieved, and, for a value of u not greatly in excess of unity, p*(/spl xi/,q,u) provides an accurate approximation for p*(/spl xi/,q) for /spl xi/ as small as -1.5 and at a modest cost in computational terms. A complete solution is obtained by employing heuristically derived criteria to effect a transition between a UTD solution employing p/sup /spl xi/,q,u/ and geometrical optics.