Hybrid Mode Matching and Method of Moments Method for the Full-Wave Analysis of Arbitrarily Shaped Structures Fed Through Canonical Waveguides Using Only Electric Currents

Abstract

A new hybrid mode matching and method of moments formulation based only on electric currents is presented in this paper. The use of only one equivalent current allows the introduction of a new set of unknowns. The chosen new unknowns are the weights related to the scattered modes that emerge from the ports to the waveguides that feed the problem. Applying this new formulation, the matrices that must be inverted are smaller and the generalized scattering matrix can be obtained directly from the solution of the resulting system of equations, so that no additional projection is needed to obtain the scattering parameters, as happens with traditional approaches with two equivalent currents. As a result, certain efficiency improvement is obtained, as can be seen when this technique is applied to the solution of H plane problems in rectangular waveguide.

Highly efficient heterogeneous modal superposition method for the full-wave analysis of arbitrarily shaped H-plane structures fed through rectangular waveguides

“…To compare the technique of [6] and the technique of this paper, the same test functions, u s , v t and ω r have to be used; the same basis functions, J q , have to be used to expand the current over the conducting limits of the cavity in both methods, as well; so that Q 1 = Q 2 in Tab. I.…”

“…If simple basis functions, such as pulses, are used to discretise the currents of [6], more unknowns will be needed to adequately characterise the ports than using plane wave modes, that is N 2 < N 1 . The cost of filling the matrices and computing the matrix products and inversions will be notably smaller for the method of this paper (see Tab.…”

“…A very popular choice to combine with mode-matching is then the method of moments, which is very general. For example, in [6], a hybrid mode-matching and method of moments technique was recently published. This technique can be applied to solve arbitrarily-shaped problems fed through one or more canonical waveguides, i.e.…”

“…a waveguide whose modes are known analytically. In [6], the ports of the problem are characterised by means of a single current formulation; in other formulations [7] the ports are solved using both electric and magnetic currents. Thanks to this simplification, the weights of the scattered modes become unknowns of the resulting system of equations; this fact is exploited to achieve certain efficiency improvement.…”

“…In this paper a fully modal characterisation of the ports is proposed, in opposition to the traditional two currents based approach of [7] or the single current based approach of [6]. This fully modal characterisation of the ports produces smaller systems of equations, so an additional efficiency improvement is achieved.…”