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

In this paper, the far-field patterns and Gaussian-beam coupling effic iencies are investigated for a double-slot antenna placed on hemispher ical lenses with varying extension lengths. The radiation patterns of a double-slot antenna on a silicon dielectric lens are computed using ray-tracing inside the dielectric lens and electric and magnetic field integration on the spherical dielectric surface. The measured radiati on patterns at 246 GHz and Gaussian-beam coupling efficiencies show go od agreement with theory. The theoretical results are presented in ext ension length/radius and radius/lambda and therefore result in univers al design curves for silicon lenses of different diameters and at diff erent frequencies. The theoretical and experimental results indicate t hat for single units, there exists a wide range of extension lengths ( ext. length/radius = 0.32 to 0.35) which result in high Gaussian-coupl ing efficiencies (50-60%) to moderately high f#'s. These Gaussian-coup ling efficiencies can be increased to 80-90% with the use of a lambda( m)/4 matching-cap layer. For imaging array applications with high pack ing densities, an extension length/radius = 0.38 to 0.39 (depending on frequency) will result in peak directivity and a corresponding Gaussi an-coupling efficiency 15-20% lower than for single units.