Octagonal Ring Antenna for a Compact Dual-Polarized Aperture Array

A wideband dual-polarized aperture array design is presented based on elements formed by a triangular configuration of octagonal rings. The octagonal ring elements are linked by capacitors and placed a defined distance from a groundplane. A broader frequency bandwidth has been achieved by placing a further layer of conductive rings above the element rings forming a metamaterial superstrate layer. Low dielectric constant material can be used to fill the space between the array rings and the groundplane, and between the elements and the superstrate layer. A dual-polarized finite ORA array has been fabricated and measured. The octagonal ring antenna array inherently exhibits a broad scan range with a stable cross polarization performance, however in practice the cross polarization depends on the feeding arrangements. Two feeding methods are discussed with a stripline feed showing best performance.