Direction finding system using planar Luneburg lens

In this paper, a novel two-dimensional Luneburg lens, composed of artificial impendence surfaces (AIS), is proposed for direction of arrival (DOA) estimation. Several detectors are mounted around the Luneburg lens to estimate the DOA of a microwave signal, owing to the surface wave can be focused perfectly on the diametrically opposite side of the lens. The desired refractive index profile of the Luneburg lens is controlled by the variable surface impendence of the unit cells, which is obtained by using an array of complementary unipolar compact photonic band gap (UC-PBG) structure inside a parallel plate waveguide. The proposed Luneburg lens with several probes, which operate in X-band region, are fabricated and measured to demonstrate the direction finding system. Both simulation and measured results show that the system has an excellent focusing ability, and the measured resolution of the system agrees very well with the theoretical value.