Prototype of a compact mechanically steered Ka-band antenna for satellite on-the-move

Abstract

We present a functional prototype of a SOTM user terminal antenna based on a planar offset Fresnel lens that implements a new mechanical steering concept previously proposed by the authors. The beam scanning is achieved by inplane translation of the feed (for zenith scanning) and axial rotation of the antenna (for azimuth scanning). The feed is as assembly of a circular polarization patch and a small planar lens. The goal of the small lens is two-fold : to adjust the primary feed directivity for a proper illumination of the main lens and to shift backwards the phase center of the patch, allowing reducing the antenna height. In the developed prototype the measured gain is 27 dBi at 30 GHz with a scan loss of 3 dB for an elevation scanning range between 18° and 53° for full azimuth. The antenna provides good circular polarization, with a cross polarization level below -14 dB. The side lobe level is below -10 dB for all beams positions. The antenna weight is less than 500 grams.