Design of circular polarised printed antennas in L-band

The generation of circular polarisation (CP) is used in satellite mobile communications and is now being considered for terrestrial microcell systems which need to exploit diversity in the radio channel to combat multipath. As a consequence low cost, low profile circular polarised antennas would be an advantage in small terminal designs. In this paper, the design of circular polarised elements is approached in two main ways; the first is to consider the element to be "naturally" circular polarised (CP); the second considers the element as the in-phase and quadrature components of linear polarised (LP) elements. As a circular polarised element a printed logarithmic antenna was considered which was designed using a semi-empirical procedure; while aperture coupled patch antennas were considered as LP elements. These elements were designed using an analysis tool based on a spectral domain full-wave model for the evaluation of the return loss and the mutual coupling in multislot-coupled microstrip patches. The design procedure and the results are shown.