Circularly Polarized Antenna Having Two Linked Slot-Rings

A broadband circularly polarized slot-ring type antenna is presented. Two square slot-rings are linked over the corner. By tuning the size of the slot-rings, both the return-loss and the axial-ratio bandwidths can be enhanced. The bandwidth is enhanced by merging the first and second bands. The first band is due to the individual loop whereas the second band is introduced by the linked structure. The structure can also be viewed as a combination of two perturbed square rings. The perturbation causes the generation of a circularly polarized wave. The measured 3 dB axial-ratio bandwidth is 1.05 GHz centered at 3.1 GHz.