
Accession Number : AD0765634
Title : Second Order Diffraction by a Ring Discontinuity,
Corporate Author : MICHIGAN UNIV ANN ARBOR RADIATION LAB
Personal Author(s) : Knott,Eugene F. ; Senior,Thomas B. A.
Report Date : JUL 1973
Pagination or Media Count : 75
Abstract : For a ring discontinuity in slope as at the base of a right circular cone, the second order (re) diffracted field is examined in the general case of bistatic scattering. It is shown that the ray paths are specified by a quartic equation whose solution is discussed. Selected results are presented, and an expression for the field contribution of any one such path is derived. An alternative formulation of the problem using equivalent currents leads to a compact expression of the complete second order field as a double line integral which, when evaluated by the stationary phase method, gives precisely the wide angle comtributions previously obtained. However, the integral expression is also finite in the direction of the axial caustic and can be used to find the caustic matching functions in second order GTD. These take the form of complementary Fresnel integrals whose practical effectiveness is verified by a comparison of the results of a numerical evaluation of the integral with the causticallymatched expression for the field in the particular case of backscattering. (Author)
Descriptors : (*DIFFRACTION, CONICAL BODIES), BACKSCATTERING, RINGS, INTEGRALS
Subject Categories : Optics
Radiofrequency Wave Propagation
Distribution Statement : APPROVED FOR PUBLIC RELEASE