Investigation of low-profile Fresnel zone plate antennas

This article presents low-profile configurations of the Fresnel zone plate antenna at Ka-band. The investigation involved progressively v reducing the focal distance of the antenna through simulations and observing the effect oil the directivity, radiation patterns, and aperture efficiency. The number of metal Zones was also varied ill the simulations. It was,found that focal distances below 0.75 lambda yielded little more directivity than the feed itself. With a single Zone, the 1.25 lambda focal distance achieved the highest overall aperture efficiency of 24%, which was a significant improvement over the larger focal distance cases. Measurements were performed to verify the simulated results. (C) 2008 Wiley Periodicals, Inc.