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The particular effects of phase matching in interactions between different wave species and interaction mechanisms pertaining to the asymptotic Green's function for a semi-infinite phased array of parallel dipoles on an infinite grounded stratified dielectric slab are addressed. The two previous parts have lead to a grouping of certain asymptotic terms, which provides physically appealing interpretations of interacting wave processes that involve slab-modulated propagating (radiating) Floquet waves (FW), slab-guided leaky waves (LW), evanescent (nonradiating) FWs and surface waves (SW), together with their associated conical edge-coupled wave constituents. Special attention is now given to the role, in these wave interaction functions,of the difference between the propagating wave numbers (i.e., the degree of phase matching) that characterizes any pair of propagating FWs and LWs, and evanescent FWs and SWs. Cutoff transitions of FWs from the evanescent to the propagating regime are described also in terms of a second wave interaction function, structured similarly to the first. In connection with applications, the interaction between SWs and evanescent FWs, as well as FW transitions from evanescent to propagating, are discussed from the perspective of scan blindness in actual arrays. Various numerical studies highlight the role of phase matching in different problem scenarios. Index Terms--Diffraction, high frequency, patch array antennas.

In this paper, a general systematic procedure is presented for defining incremental field contributions. They may provide effective tools to describe a wide class of scattering and diffraction phenomena at any aspect, within a unitary, self-consistent framework. This procedure is based on a generalization of the incremental theory of diffraction (ITD) localization process for uniform cylindrical, local canonical problems with elementary source illumination and arbitrary observation aspects. In particular, it is shown that the spectral integral formulation of the exact solution for the local canonical problem may also be represented as a spatial integral convolution along the longitudinal coordinates of the cylindrical configuration. Its integrand is then directly used to define the relevant incremental field contribution. For the sake of convenience, but without loss of generality, this procedure is illustrated for the case of local wedge configurations. Also, a specific suitable asymptotic analysis is developed to derive new closed form high-frequency expressions from the spectral integral formulation. These expressions for the incremental field contributions explicitly satisfy reciprocity and are applicable at any incidence and observation aspect. This generalization of the ITD localization process together with its more accurate asymptotic analysis provides a definite improvement of the method. Index Terms--Diffraction, high frequency, incremental theories, scattering.

A uniform, high-frequency solution is presented for the electromagnetic field radiated at finite distance by a semi-infinite array of elementary electric dipoles placed on an infinite grounded dielectric slab. This solution is useful for the efficient analysis of printed arrays. The field is represented in terms of a series encompassing propagating and evanescent truncated Floquet waves together with their corresponding diffracted rays, which arise from the edge of the array. The high-frequency formulation also includes surface and leaky wave contributions excited at the array edge. The diffracted waves contain discontinuities which compensate the disappearance of surface, leaky and truncated Floquet waves at their pertinent shadow boundaries. The rich variety of wave phenomena and the corresponding Geometrical Theory of Diffraction generalization will be presented in Part II of this paper. Index Terms--Diffraction, high frequency, patch array antennas.

Recently, an incremental theory of diffraction (ITD) has been introduced which provides a self-consistent, high-frequency description of a wide class of scattering phenomena within a unified framework. Explicit expressions of the incremental diffracted field contributions have been obtained for a plane-wave illumination of wedge-shaped configurations and observation points at a finite distance from the incremental point. In this paper, this method is extended to treat the case when both the source and the observation point are at finite distance from the local incremental point along the edge. To this end, a spectral-domain approach is used to derive a spectral-integral representation for the incremental field contribution. The latter is asymptotically evaluated to find high-frequency closed-form expressions which are uniformly valid at any incidence and observation aspects, including caustics and shadow boundaries of the corresponding ray-field description. The expressions of the incremental diffraction coefficients explicitly satisfy reciprocity. Numerical results are presented and compared with those obtained from different techniques.

The problem of scattering by a semi-infinite grounded dielectric slab illuminated by an arbitrary incident [TM.sub.z] polarized electric field is studied by solving a new set of 'fringe' integral equations (F-IEs), whose functional unknowns are physically associated to the wave diffraction processes occuring at the truncation. The F-IEs are obtained by subtracting from the surface/surface integral equations pertinent to the truncated slab, an auxiliary set of equations obtained for the canonical problem of an infinite grounded slab illuminated by the same source. The F-IEs are solved by the method of moments by using a set of subdomain basis functions close to the truncation and semi-infinite domain basis functions far from it. These latter functions are properly shaped to reproduce the asymptotic behavior of the diffracted waves, which is obtained by physical inspection. The present solution is applied to the case of an electric line source located at the air--dielectric interface of the slab. Numerical results are compared with those calculated by a physical optics approach and by an alternative solution, in which the integral equation is constructed from the field continuity through an aperture orthogonal to the slab. The applications of the solution to an array of line currents are also presented and discussed. Index Terms--Fringe integral equation.

This paper presents calculations of the mutual admittance between two slots on a ground plane that are the primary feed of an elliptical dielectric lens antenna. This admittance may also be regarded as the basic constituent of a Galerkin method of moments formulation for the analysis of more complex feeding arrangements of slot antennas and coplanar waveguide circuits. It is found that the contribution of the reflection mechanisms inside the lens significantly affects the mutual admittance especially for H-plane coupling. Index Terms--Lens antennas, printed antennas.