The variations of omnidirectional circularly polarized antennas for satellite telemetry/telecommand applications

Abstract

In this paper the design production and results of different types of omnidirectional and circularly polarized antennas for satellite communication applications such as telemetry or telecommand are explained. These antennas consist of identical inclined slots placed on a circular waveguide and two radially outward parallel cylindrical plates in order to provide circular polarization. The feeding of the antenna is provided by a special transition structure between rectangular waveguide to circular waveguide. The first type of antenna contains eight identical slots on the circular waveguide which gives about 3 percent frequency (impedance) bandwidth for 10 dB return loss. This antenna provides gain variation of about 0.7 dBi and axial ratio lower than 1 dB in the azimuth plane at the center frequency. The second type which is designed to enhance the frequency bandwidth includes nonidentical slots on the circular waveguide where the length of four among eight slots is reduced. This enhanced version increases impedance bandwidth to 5.8 percent. The gain variation and axial ratio performances of the second type antenna are slightly lower as compared to first version at the expense of improvement in bandwidth, however the results of both types are still satisfactory for satellite applications. © 2017 Elsevier B.V. All rights reserved.