Circularly polarized multi-beam lens antenna system for High Altitude Platforms (HAPS)

In this paper a 30 GHz multi-beam antenna prototype has been developed for High Altitude Platform Stations (HAPS) applications. When mounted on a HAPS at the stationary altitude of 21 Km, this antenna provides cellular coverage on the ground. The antenna consists of a dielectric lens fed by circular waveguides terminated with small horns. Circular polarization is achieved by integrating a polarizer in the waveguide feed. Due to the lens symmetry, each beam presents the same radiation pattern. The global antenna system has been designed, realized and measured. The prototype fulfils the initial specifications and shows an impedance bandwidth at -10 dB of 19%. Moreover an axial ratio lower than 3 dB is achieved within this bandwidth in a ±5° angular range.