Cross Polarization Isolation Improvement in Electrically Small Prime-focal Reflector Antennas by Reducing Near Field Scattering

Wide coverage beams are usually generated with Medium or Low Gain Antennas with typical Edge of Coverage (EoC) Gain in the range of 15–25 dBi. Such Antennas when realised in Prime Focal Reflector configuration suffer from poor Cross Polarization Isolation due to the blockage effects of feed and struts. In this work, the shape of the a 0.9m reflector is distorted in such a way that the Near Field around the feed is reduced by 15–20 dB relative to unshaped reflector. The shaping has been carefully carried out in order not to lose Gain and aperture efficiency. The performance of Reflector is analysed with mono-groove polarizer based profiled horn CP feed in S-Band. The resultant design has a EoC Gain of >21 dBi in +/-4.25 deg coverage and has shown > 12 dB improvement in Cross Polarization Isolation when compared to Unshaped paraboloid.