A double line integral representation of the mutual coupling between openended waveguides of arbitrary cross section is presented, which is useful to speed up calculations inside the framework of a Galerkin method of moments. © 1997 IEEE.

A double line integral representation of the mutual coupling between open-ended waveguides of arbitrary cross section is presented, which is useful to speed up calculations inside the framework of a Galerkin method of moments.

Incremental diffraction coefficients at the edge of a circular horn (CH) are derived on the basis of the Incremental Theory of Diffraction (ITD). The resulting distributed diffracted field contributions are used to predict mode radiation in the near zone, as well as to the reciprocal problem of EM coupling of a spherical wave into the CH. Second order, incremental diffraction contributions are also included to preserve accuracy at aspects below the aperture plane. For simplicity purposes, the analysis is restricted to the scalar case, with hard boundary conditions on the walls. Thus, guidelines are provided for the more general EM case.

The equivalence between physical optics (PO) and aperture integration (AI) is extended to evaluate the coupling between two open-ended waveguides of arbitrary cross-section. Furthermore, a Kirchhoff-type coupling coefficient is derived in terms of a double line integration of incremental coupling coefficients. A useful tool when the mutual impedance of two modal distributions has to be calculated in the framework of a method of moment procedure is provided which is formulated in terms of mode-shaped basis functions.