Satellite broadcasting of 4K/8K ultra-high definition television (UHDTV) was launched in Japan in December 2018. Because this system uses the amplitude and phase shift keying (APSK) modulation scheme, there is a need to improve the non-linear characteristics of the satellite transponders. To meet this requirement, we have been developing a 120-W-class Ku-band solid state power amplifier (SSPA) as a replacement for the currently used traveling wave tube amplifier (TWTA). In this study, we developed a gallium-nitride (GaN) SSPA and linearizer (LNZ). The SSPA achieved an output power of 120W while maintaining a power added efficiency (PAE) of 31%. We evaluated the transmission performance of 16APSK in this SSPA channel in comparison with that in the TWTA channel.

Japan Broadcasting Corporation (NHK) started test satellite broadcasting of ultra-high-definition television (UHDTV) on August 1st, 2016. The test broadcasting is being provided in the 12-GHz (11.7 to 12.75GHz) band with right-hand circular polarization. In 2018, left-hand circular polarization in the same frequency band will be used for satellite broadcasting of UHDTV. Because UHDTV satellite broadcasting uses the 16APSK modulation scheme, which requires a higher carrier-to-noise ratio than that used for HDTV in Japan, it is important to mitigate the cross-polarization interference. Therefore, we fabricated and tested a dual-circularly polarized offset parabolic reflector antenna that has a feed antenna composed of a 2×2 microstrip antenna array, which is sequentially rotated to enhance the polarization purity. Measured results showed that the fabricated antenna complied with our requirements, a voltage standing wave ratio of less than 1.4, antenna gain of 34.5dBi (i.e., the aperture efficiency was 69%), and cross-polarization discrimination of 28.7dB.

In December 2018, satellite broadcasting for 4K/8K ultra-high-definition television (UHDTV) will begin in Japan. It will be provided in the 12-GHz (11.7 to 12.75GHz) band with right- and left-hand circular polarizations. BSAT-4a, a satellite used for broadcasting UHDTV, was successfully launched in September 2017. This satellite has not only 12-GHz-band right- and left-hand circular polarization transponders but also a 21-GHz-band experimental transponder. The 21-GHz (21.4 to 22.0GHz) band has been allocated as the downlink for broadcasting satellite service in ITU-R Regions 1 (Europe, Africa) and 3 (Asia Pacific). To receive services provided over these two frequency bands and with dual-polarization, we implement and evaluated a dual-band and dual-circularly polarized parabolic reflector antenna fed by 12- and 21-GHz-band microstrip antenna arrays with a multilayer structure. The antenna is used to receive 12- and 21-GHz-band signals from in-orbit satellites. The measured and experimental results prove that the proposed antenna performs as a dual-polarized antenna in those two frequency bands and has sufficient performance to receive satellite broadcasts.