Omnidirectional and Circularly Polarized Transceiver Antenna for TT&C Communication in Satellite Systems

In this study, the design of an omnidirectional and circularly polarized waveguide antenna used as a transceiver in telemetry/telecommand applications of satellite systems is described. Instead of separate transmitter (TX) and receiver (RX) antennas used in space segment, the proposed antenna can realize transmit and receive operations (TX/RX) simultaneously, which results in the reduction in the number of antennas. The proposed antenna has two sets of inclined slots on circular waveguides with different radii. The below slots operate at TX frequencies around 11.75 GHz, and above slots make an effective radiation at RX frequencies around 14 GHz. In the antenna design, while metallic disks extending away from circular waveguides improve axial ratio performance, a special dual-band rectangular-to-circular waveguide mode converter provides better omnidirectionality. The designed antenna has 10 dB impedance bandwidth more than 150 MHz and 415 MHz at TX and RX frequencies. In azimuth plane, gain variation is lower than 2 dBi, axial ratio is also lower than 1.63 dB at both frequency bands. In elevation plane, minimum gain is found as -5 dBi and axial ratio is below almost 3 dB within 55° beamwidth.