Dual-Polarized Planar Feed for Low-Profile Hemispherical Luneburg Lens Antennas

A dual-polarized planar feed antenna suitable for illuminating a hemispherical Luneburg lens on a ground plane operating at Ku band is presented. Compared to a waveguide feed, the planar antenna has the advantage of reducing the overall profile of the lens system. The planar feed is realized using a 2 × 2 array of stacked patches, and orthogonal polarizations of the patches use different coupling methods to increase isolation between the two ports of the device. Simulated S-parameters, radiation patterns, gain, directivity, and efficiency of the planar feed are compared with measured results. Measured radiation patterns and gain are also presented for a commercial Luneburg lens illuminated by the planar feed, to characterize the combined lens/feed performance and to validate the utility of the planar feed design.