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Circular Polarization Wide-angle Beam Steering at Ka-band by In-plane Translation of a Plate Lens Antenna

Lima, E.B. ; Matos, S.A. ; Costa, J.R. ; Fernandes, C. A. ; Fonseca, N.

IEEE Transactions on Antennas and Propagation Vol. 63, Nº 12, pp. 5443 - 5455, December, 2015.

ISSN (print): 0018-926X
ISSN (online): 0018-926X

Scimago Journal Ranking: 1,74 (in 2015)

Digital Object Identifier: 10.1109/TAP.2015.2484419

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A simple mechanical beam steering antenna concept is proposed for ground mobile terminals of Ka-band satellite and high altitude platform (HAP) providing broadband access services. The wide-angle elevation beam steering is achieved by inplane translation of a thin off-set flat lens in front of a stationary primary feed while full azimuth coverage is obtained by simple 360º rotation of the lens. A new strategy is also proposed to reduce the effective F/D of the focusing system and consequently the total antenna height without increasing beam distortion: a second small
flat lens is added on top of the primary feed to create a virtual focus located well below the feed phase center. The challenge is to conciliate high gain both with wide beam scanning and reduced antenna height. Design rules are presented for this antenna concept along with a 27.3 dBi gain fabricated example for the uplink Ka-band (29.5-30 GHz), with circular polarization, 0 to 50º elevation scan, better than 2.8 dB scan loss and an effective F/D of only 0.55. Both lenses are 3.35 mm thick, formed by a suitable assembly of phase shifting unit cells with less than 0.4 dB of transmission loss in simulation. The main lens dimensions are 195 mm × 145 mm and its weight is 215 g. Total antenna height, including the feed is 84 mm.