Multiband Antenna Links To Mobile Satellite-Communications Terminals

MOBILE SATELLITE TERMINALS are of increasing interest for military applications requiring rapid deployment and changes in operational positions. In order to support the trend away from large satellite ground stations, Stephen Targonski of the Wideband Tactical Networking Group at MIT Lincoln Laboratory (Lexington, MA) designed a multiband reflector antenna for an on-the-move satellite-communications terminal. The antenna was designed to operate with a variety of modern and future military communications satellites requiring operation at multiple frequencies and polarizations.

The author worked with simulations based on the High Frequency Structure Simulator (HISS) from Ansoft to model the feed structure. Tiera's GRASP8W code was used for the analysis of the reflector antenna. The main reflector is 16 in. in diameter. The subreflector is attached to the aluminum feed support using a "feedome" comprised of ROHACELL 100WF foam material. The antenna was designed to cover the 20-, 30-, and 44-GHz bands using a dualband polarizer with circular polarization at 30 and 44 GHz. The polarizer is based on a ridged dielectric-filled circular waveguide.

Measurements on the mobile satellite antenna structure were made with a NSI near-field scanner, with peak sidelobes about 12 dB below the main beam at 30 GHz. The measured gain of the antenna was 36.6 dBi at k-band, 40.2 dBi at Ku-band, and 43.9 dBi at Q-band, with corresponding aperture efficiencies of 59, 64, and 68 percent for those three frequency bands, respectively. See "A Multiband Antenna for Satellite Communications on the Move," IEEE Transactions on Antennas and Propagation, October 2006, Vol. 54, No. 10, p. 2862.

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