A 12-GHz (11.7 to 12.75 GHz) band satellite service with dual-circular polarization is expected for transmission channels to deliver advanced broadcasting services such as 8K (Super Hi-Vision). A right- and left-circularly polarized parabolic reflector antenna will make it possible to receive services provided over the dual-circular polarization with a single reflector antenna. Therefore, we designed a dual-polarization microstrip antenna array for the feed antenna of an offset parabolic reflector antenna. Simulation results showed the voltage standing wave ratio was less than 1.4 and the cross polarization discrimination (XPD) was more than 29 dB. A dual LNB (Low Noise Block Converter), which has two local oscillators corresponding to right- and left-circular polarizations, is also required for the dual-polarization receiving antenna to carry the received signals on a single cable. To evaluate the feasibility of the dual LNB, we fabricated and measured the LNB integrated with a parabolic reflector. The measured results showed the aperture efficiency was more than 76 %, XPD was more than 26 dB and the noise figure of the LNB was less than 1 dB. On the other hand, a 21-GHz (21.4 to 22.0 GHz) band satellite broadcasting system is also being studied as a means of delivering 8K, 3DTV, and other advanced forms of broadcasting. Then, we fabricated a 21-GHz band parabolic reflector antenna, which has a 60-cm offset reflector, for common reception equipments in condominiums and so on. The reflector is made of a metallic mesh and fiber reinforced-plastics for survival wind speed and weight saving. The measured results showed that the aperture efficiency was 74 % and that the radiation pattern complied with the reference pattern in Recommendation ITU-R BO.1900.
