Omnidirectional and Circularly Polarized Slotted Antenna Array With Increased Bandwidth Performance by Using Nonidentical Waveguide Slots

Abstract

In this paper the design production and results of an omnidirectional and circularly polarized antenna for satellite communication applications such as telemetry or telecommand are explained. The antenna is fed by a special transition structure between rectangular waveguide to circular waveguide in order to provide symmetrical circular waveguide mode of TM01 and eliminate dominant but asymmetric mode of TE11. The radiation part on the antenna has the geometry of inclined waveguide slots placed in a rotationally symmetric way on a circular waveguide and two radially outward parallel cylindrical plates in order to provide circular polarization. In the design of the antenna nonidentical slots are used on the circular waveguide where half of the total number of slots is reduced to increase the bandwidth of the antenna. The realized antenna is found to give about 5-6% impedance bandwidth around 12GHz where it is just approximately 2.5% when all slots in array are identical. The usage of nonidentical slots results in degradation of gain variation and axial ratio performances as compared to the antennas with identical slots, however it still performs gain variation less than 3dB over full azimuth plane and axial ratio under 3dB over full azimuth plane and elevation beamwidth of minimum 50 degrees for the given bandwidth.