Characteristic Mode Analysis of a Circular Polarised Rectangular Patch Antenna

This paper discusses the analysis of a circular polarised patch antenna with the theory of characteristic modes. The objective is to find a feeding position and achieve the purest possible form of a polarised farfield pattern. By using characteristic mode analysis (CMA) the best case pattern supported by the structure can be extracted. Therefore the most important modes for circular polarisation are isolated and used for mode combination. The resulting pattern is used as a reference for envelope correlation coefficient (ECC) with the second pattern provided by regular field solver. By changing the feed type and or position different results can be characterised in their polarisation purity and therefore axial ratio.