An efficient full-wave-MoM for RLSA antennas

We present a computationally efficient method of moments (MoM) formulation for full-wave analysis and design of radial line slot antennas (RLSAs). RLSAs provide a simple, high-efficiency, low-cost alternative solution to microstrip arrays for high frequency microwave and millimeter wave applications. An RLSA consists of a parallel plate waveguide in which a radial propagating mode is excited to feed a slot distribution etched on the upper metallic plate. The slot arrangement and the feeding mode selection determine different antenna radiation patterns, shapes and polarization. The efficiency of the presented numerical method is based on an ad-hoc representation of the interior problem (electrically large circular cavity) Green´s function, based on a series expansion of radial modes. This allows a very efficient analysis, with a small computational effort, of the entire antenna, including the effect caused by the metallic ring which encircles the parallel plate waveguide. We performed numerical tests both on the Green´s function and on the MoM admittance calculation, in order to check the convergence rate of our ad-hoc representation. Furthermore, we compared it with a commercial general purpose MoM software package for simple slot arrangements and for complete RLSAs. The proposed formulation showed excellent results with much less computational effort.