TABLE OF CONTENTS Hybrid methods were introduced in the early 1970s for solving some difficulties encountered with asymptotic methods. A typical situation is the diffraction of an object which is large compared to the wavelength but which has locally in some specific areas a complexity in the geometry (fine details) or in the boundary conditions (thick penetrable material) which fall outside the domain of applicability of asymptotic methods. To this category of targets, we also need to add singularities of the surface for which no explicit expressions for the coefficient of diffraction exist.
The hybrid methods have been continuously developed since that time. Nowadays, the same types of problems are still of interest, but the position of the problem is changed since hybrid methods are now developed for augmenting the possibilities of numerical techniques by reducing the storage and the CPU time.
A short review on the different types of hybrid methods which have been developed or proposed in the literature is given in Reference 1. Several synthesis papers on specific applications of hybrid methods have also been published by Newman [2], Medgyesi-Mitschang and coworkers [3, 4] and Thiele [5].
The different methods which have been proposed in the literature are generally characterised as either field-based or current-based analysis. The field-based approach is particularly attractive for radiation problems where the radiator is in proximity of large surfaces for which GTD solutions through ray techniques apply. A typical example is a ?/2 wire antenna in front of a...
