A dual band ridged waveguide feed structure for satellite television reception

The design and simulation of a dual band, coaxial waveguide feedhorn structure for a satellite reflector dish is presented using CST´s Microwave Studio™. The feedhorn operates on the satellite television frequencies, commonly referred to as the Direct Broadcast Satellite (DBS) frequencies of, 10.7-12.75, 19.7-20.2 and 29.5-30 GHz. The feedhorn structure consists of two separate waveguides that are placed inside one another and at the focal point of the reflector dish which will be illuminated with circular polarization from a geostationary satellite. The inner circular waveguide is filled with a dielectric material, Rexoilte™ that reduces the physical size of the waveguide but also serves to protect against moisture ingress and acts as a matching stub device. The outer circular waveguide is ridged in order to reduce the cut-off frequency for the first mode and to increase the bandwidth between the dominant TE₁₁ mode and the second mode of operation, TM₀₁. A reduction in overall size is seen compared with previous work.