Turnstile-Junction-Based Omnidirectional Antennas for Space Applications [Antenna Applications]

Omnidirectional biconical antennas are widely used in satellites as a constituent part of the telemetry, command, and ranging (TC&R) RF subsystems. They provide a toroidal radiation pattern, and are mainly used in combination with other low-gain antennas to provide an omnidirectional pattern [1] during transfer orbit, and for on-station communications of the satellite with ground. The design of the feeding network of this type of antenna is critical, since the receiving antenna is situated right on top of the transmitting antenna. Previously used feeding configurations resorted to cables and intermediate connectors to reduce mass and envelope. In this paper, a novel feeding configuration - entirely waveguide based - is presented as a tradeoff between mass and robustness. It is based on the use of a turnstile junction to avoid weak links and to provide a robust and reliable design, a must in space applications. Considerations related to the design of the radiating elements and manufacturing will also be discussed, as well as a comparison between the simulated and measured performance of the final prototype of the omnidirectional antenna.