Experimental results for a metamaterial Lüneburg lens

This paper presents experimental results obtained from the characterization of a mematerial Lüneburg lens. Previously, a finite element numerical analysis was done in order to determine the compromise between the constitutive and the geometrical parameters. It was shown that is possible to control the effective refractive index of a single cell by only changing the resonator height, where the highest amount of current passes through. Next, the resonators were placed following the needed refractive index distribution for a Lüneburg lens. The dielectric substrate used was 1.6 mm thick and the metamaterial was printed inside a 100mm diameter circle. The antenna excitation was through a vertical monopole adjusted to sent the input impedance to $50\ \Omega$ at 10 GHz. Transmission measurements were done in a semi-anechoic chamber under different excitation conditions. It was obtained a rise of 20 dB over the measured signal relative to the input one coming from the monopole antenna. The radiated field was linearly polarized and a cross polarization rejection of 18.5 dB was also verified.