Mark Vrancken

Characteristic aperture modes for the mutual coupling analysis in finite arrays of aperture-coupled antennas

Summary Calculation of mutual coupling in finite arrays of aperture-coupled antennas with an arbitrarily shaped aperture is seriously impeded by the number of unknowns necessary to describe the aperture field. Entire domain expansion functions are extracted numerically from the equation tha has to be satisfied by the equivalent magnetic current on the aperture of asingle antenna element by applying the well developed theory of Characteristic Modes. The resulting weighted eigenvalue equation gives an orthogonal set of eigenmodes which can be ordered according to their contribution in therealpower flow through the aperture. It is shown, that even for ‘near field’ quantities like S -parameters, only a limited number of characteristic modes is sufficient to characterize the electromagnetic coupling through the aperture. The procedure was used in a methodof moments code and results are compared to measurements and other calculations from literature.

The use of hierarchy in modeling tools for planar structures

Since 1985, the K.U. Leuven has been involved in the analysis of general planar antennas. In 1993, a strategy was developed in order to incorporate the work done in a framework called MAGMAS (Model for the Analysis of General Multilayered Antenna Structures). Essential is the fact that MAGMAS uses a multi-level approach. In our view this is crucial in order to reach the ultimate goal: an accurate, interactive, one-pass CAD tool to design planar and quasi-planar antennas. Antenna examples are given, illustrating the physical structures that can be analyzed with the framework.

Alternative formulation of the electric field in a stratified medium applied with a mixed spectral-spatial coupling calculation for integral equation modelling of vertical current sheets

Integral equation modelling of electromagnetic radiation and interference phenomena in planar circuits and antennas offers exact solutions usually at the cost of excessive computation time, especially when arbitrary 3D conducting surfaces are involved. However, for most of these problems, the geometry can be restricted to the 2.5D case, that is, only horizontal (parallel to layer structure) and vertical conducting surfaces (normal to the dielectric layers) are present. This paper reports progress in the full wave analysis of these structures. An alternative but generally valid form for the electric field in the stratified medium is presented. For the 2.5D geometry, but modelling all current components, the availability of analytical expressions for the Greens functions in the spectral domain is then exploited to perform a mixed spectral and spatial calculation of the matrix elements required to solve the integral equation. An overall reduction of computation time is hereby envisaged. Numerical results of actual 2.5D structures are provided.