Circularly polarized square ring slot patch antennas

The aperture coupled feeding technique has been demonstrated to be effective in enlarging the impedance bandwidth of patch antennas. Moreover, it can improve the Axial Ratio (AR) bandwidth of a circularly polarized (CP) patch antenna [1]. Recently, a novel slot coupling feeding technique has been presented in [2], where the two orthogonal microstrip feeding lines of a dual-linearly polarized patch are coupled to the square radiating square patch through a square ring slot. There, it has been shown that the symmetry properties of the square-slot coupling geometry can give good performance in terms of port isolation and radiation pattern characteristics. In this paper, the coupling technique in [2] has been applied to realize a singlefeed CP square patch. Although single-feed CP patches exhibit smaller AR percentage bandwidths with respect to dual-feed CP antennas, their layout is more compact and then suitable for the implementation of electrically large arrays. © 2010 IEEE.