Prolate Ellipsoidal Lens for Antenna Systems Providing Multiple Asymmetric Beams

A 3-D shaped prolate ellipsoidal dielectric lens is designed to produce multiple asymmetric beams in Ka-band. Such radiation characteristics are useful in applications where the antenna system is mounted on platforms flying above Earth and the shape of the footprints have to be carefully controlled for different elevation angles. A set of design rules is introduced and the final designs are optimized using full-wave time-domain methods. A fully operational Ka-band antenna subsystem has been prototyped and measured. The final antenna lens has axes lengths of 62.3 mm and 57.8 mm and provides a maximum gain of 21 dB. When mounted on a stabilized platform at the altitude of 21 Km (a typical HAPS scenario), this antenna provides 19 circular ground footprints of 5 Km diameter each. Radiation pattern measurements show that such a lens reduces the natural beam footprint elongation unavoidable with traditional spherical lenses and confirm the validity of the proposed system.