Extremely wideband waveguide polariser system for polarisation alignment

The letter reports on a system consisting of two quarter-wave polarisers in tandem for polarisation alignment of linearly polarised satellite signals. The signal can be received with the correct polarisation simply by rotating the polariser which is closest to the feed horn. The required isolation in the frequency bands 10.95-12.75 GHz (Rx) and 14.0-14.5 GHz (Tx) is 35 dB on the axis for the total antenna system consisting of reflectors, horn, polariser system and orthomode transducer. This requirement cannot be met when existing polarisers are used and when a ±90° rotation is required. By using a new type of polariser, 38 dB isolation has been measured for the polariser system over the entire frequency band and over the entire range of rotation, with transmission loss below 0.15 dB and return loss below -25 dB (VSWR <1.12). The total length of the system is approximately 300 mm