DOUBLE-SLOT ANTENNAS ON EXTENDED HEMISPHERICAL AND ELLIPTIC QUARTZ DIELECTRIC LENSES

In this paper, the theoretical far-field patterns and Gaussian-beam coupling efficiencies are investigated for a double-slot antenna placed on quartz hemispherical lenses with varying extension lengths. The radiation patterns of the double-slot antenna are computed using ray-tracing inside the lens and electric and magnetic field integration on the spherical dielectric surface. The theoretical results are equally valid for double-dipole, log-periodic, and spiral antennas, and are presented in extension length/radius and radius/lambda. Therefore, the results yield universal design curves for quartz lenses of different diameters and at different frequencies and using different antennas. The results indicate that for single units, there exists a wide range of extension lengths (ext. length/radius=0.61 to 0.76) which result in high Gaussian-coupling efficiencies to moderately high f/# systems. For imaging array applications with high packing densities, an extension length/radius=0.82 to 0.93 (depending on frequency) will result in peak directivity and highest packing density but lower Gaussian-coupling efficiencies.