Annular slot antennas on extended hemispherical dielectric lenses

Annular slot antennas (ASA) at 35 GHz and 94 GHz have been analyzed by measuring their input impedance, computing radiation patterns, and extracting therefrom quantities relevant to quasi-optical systems. A full-wave analysis in the spectral domain allows the rigorous modeling of the fields in the several dielectric layers that form the antenna and of the radiation patterns. A technique for equalizing the E and H plane beamwidths is presented. One design at 94 GHz indicates a directivity of 22 dB, Gaussian coupling efficiency of 84 percent, a sidelobe level of 17 dB, and intensity front-to-back ratio of 30 dB.