The ACTS multibeam antenna

The Advanced Communication Technology Satellite (ACTS), to be launched in 1993, is introduced briefly, and then the Ka-band multibeam antenna, consisting of electrically similar 30 GHz receive and 20 GHz transmit offset Cassegrain systems utilizing orthogonal linear polarizations, is described. Dual polarization is achieved by using one feed assembly for each polarization in conjunction with nested front and back subreflectors, the gridded front subreflector acting as a window for one polarization and a reflector for the other. The antennas produce spot beams with approximately 0.3 degrees beam width and gains of approximately 50 dBi. High surface accuracy and high edge taper produce low sidelobe levels and high cross-polarization isolation. A brief description is given of several Ka-band components fabricated for ACTS. These include multiflare antenna feedhorns, beamforming networks utilizing latching ferrite waveguide switches, a 30 GHz HEMT low-noise amplifier, and a 20 GHz TWT power amplifier.<
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