Direct singular integral equation methods in scattering and propagation in strip- or slot-loaded structures

Problems of three-dimensional (3-D) scattering/hybrid-wave propagation for strip- or slot-loaded structures are often formulated in terms of systems of singular integral-integrodifferential equations (SIE-SIDE) of the first kind. Proper handling of the singular part of the kernels constitutes a major difficulty in carrying out method of moments (MoM). Three powerful techniques explored in the present paper provide efficient solutions by direct recourse to the theory of singular integral equations. In contrast to low-frequency methods wherein similar concepts are utilized for electrically narrow strips/slots, the proposed procedures are applicable uniformly to the whole range of widths from very narrow to very wide scatterers with remarkable accuracy. Numerical results are presented to validate and compare to one another the various numerical codes.