A slotted hollow ring element for Ku-band high-efficiency circularly polarized reflectarrays

Based on the idea of a single-layer multiresonance structure for a linearly polarized reflectarray, a novel slotted hollow ring element is presented for Ku-band high-efficiency circularly polarized reflectarrays. The appropriate geometry parameters are determined by studying the effects of incident angle on the element reflection coefficient. Compared to the conventional microstrip ring element, it can provide a broader CP bandwidth and more accurate phase compensation. Then, by using the angular rotation technique, an offset 137-element reflectarray operating at 12 GHz is designed and fabricated to demonstrate the superior performance of the element. The measured result shows that the reflectarray offers a maximum efficiency of 66.13% at 12.3GHz. Meanwhile, the efficiency is better than 60% over a 16.8% bandwidth (11.1GHz-13.1GHz). The overlapping 1-dB gain bandwidth and 3-dB axial-ratio bandwidth can reach 20%.