120-W Ku-Band GaN SSPA with Diode Linearizer for Future Broadcasting Satellite

In December 2018, satellite broadcasting of ultrahigh definition television will begin in Japan. The broadcasting will be provided with an amplitude and phase shift keying (APSK) modulation scheme. The non-linear characteristics of the satellite broadcasting transponders need to be reduced, and to do this, we have been studying a 120-W gallium-nitride (GaN) high power amplifier (HPA) for broadcasting satellites in the Ku band. In this work, we describe a GaN HPA and linearizer (LNZ) we have developed. The HPA was fabricated with $\pmb{0.15-\mu}\mathbf{m}$ GaN high electron mobility transistor (HEMT) technology and delivered an output power of 120 W while maintaining a power added efficiency (PAE) of 31%. The LNZ was applied to the HPA for improving the linearity of the HPA. By applying LNZ, gain compression within 2 dB and phase modulation within 5 degrees were achieved. As a next step, we will perform transmission experiments with a 16APSK signal.