Multifunction single-package antenna system for spin-stabilized near-synchronous satellite

An antenna system is described for a spin-stabilized satellite with its axis normal to the orbital plane. Three antennas in a compact lightweight package comprise the antenna system: a switched-beam
X
-band transmitting antenna, an omnidirectional
X
-band receiving antenna and an omnidirectional VHF telemetry antenna. The first is a cluster of eight circularly polarized horns pointed radially outward every 45 degrees about the spin axis. An eight-throw solid-state waveguide switch turns on that horn currently pointing most nearly to earth. This is accomplished by providing the switch with electrical signals from a logic circuit operating on information from earth sensors. The second antenna is a circularly polarized biconical horn located above the cluster of transmitting horns. Its sense of polarization is opposite that of the transmitting antenna, and a filter in the transmission line to the receiver insures the required isolation. The third antenna is obtained by feeding across the gap between the two
X
-band antennas and exciting the external surfaces to radiate in a linearly polarized mode. Total weight of the three-antenna package is less than
4\frac{1}{2}
pounds; it occupies a volume less than 10 inches square by 8 inches high above the top panel of the satellite.