Wideband, high-efficiency, circularly polarized slot elements

The authors discuss a number of wideband, high-efficiency slot elements that when appropriately fed are inherently circularly polarized. The elements have been derived by applying the principle of complementarity to a class of microstrip patch radiators that use perturbation techniques to provide circular polarization. These novel circularly polarized slot radiating elements have been incorporated into high-efficiency broadband arrays. Arrays ranging from 0.32 m (256 elements) to 0.7 m (1024 elements) have been built and tested at Ku-band. In all cases, efficiencies of greater than 50% have been achieved over an approximate 10% bandwidth. Demonstrated polarization purity is quite good, achieving better than 1.5 dB axial ratio over a 10% bandwidth.<>