Evaluation of edge effects in slot arrays using the geometrical theory of diffraction

Abstract
The geometric theory of diffraction (GTD) is applied to evaluate efficiently the coupling coefficient associated with the design of a waveguide-fed longitudinal shunt slot arrays. The coupling coefficient is proportional to the reaction integral between the field of a slot and the equivalent current distribution of another slot. Using an approximate form of the Green's function for the wedge, it is shown that the edge-diffraction field due to each slot is practically equal to the field of a suitable 'mirror image' of such slot. In this way the actual coupling coefficient can be decomposed into a sum of coupling coefficients between slots on an infinite ground plane. The latter can be evaluated very efficiently so that inclusion of edge effects does not slow down the design procedure. The same approach also allows the computation of the relation between the self-admittance with and without the edge. Some test cases are provided which show that the overall error of this approximation can be neglected since it is comparable with the error due to mechanical tolerances.

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