A full-wave hybrid method for the fast analysis of SIW-based antennas

We present a full-wave code based on the method of moments (MoM) and mode matching (MM), capable of efficiently and accurately analyzing complex substrate-integrated-waveguide (SIW)-based antenna structures. The field inside the structure is conveniently expressed in terms of the radial transmission-line representation of the pertinent Green´s function, which is split into parallel-plate-waveguide (PPW) and post-scattered contributions. This enables to efficiently calculate the required field quantities by solving a linear system which is obtained by enforcing the opportune boundary conditions on posts. In the presence of coupling among various layers or radiating slots, the equivalence principle is invoked to model the field distribution on the slots with equivalent magnetic currents. This allows formulating the problem in terms of the standard Method-of-Moments procedure. The accuracy and computational effort is superior with respect to general-purpose commercial full-wave solvers.