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 18º and 53º 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.