A Horn Antenna Design with Novel Waveguide Polarizer for Mobile Satellite Communications Applications

Conventional polarizers usually include complicated corrugations and lossy insertions such as an iris, septa and dielectric slab, causing performance degradation and fabrication difficulties. At high frequencies, such fabrication difficulties and lossy components are limiting factors to achieving low costs and high performance. In this paper, a novel waveguide-type polarizer with an oval shaped cross-section that is inclined at a +/- 45 degrees angle for right-handed and left-handed circular polarization is presented. Due to the oval cross-section, the polarizer can be easily fabricated by mechanical processing with considerable performance. The proposed polarizer structure is fabricated using a pyramidal horn with a square aperture. From measured results, it is confirmed that the horn antenna has a gain of 9.4 dBi at 30.5 GHz with 20 dB cross-polarization level. The return loss is below -15 dB from 28 GHz to 34 GHz, and the axial ratio bandwidth is about 18% at a 3-dB level. This horn antenna will be applied to a feeder design with electrical beam scanning for a reflector-based mobile satellite antenna terminal.