A GaN/SiC UHF PA for Particle Accelerators with 100-145V Quasi-Static Drain Modulation

This publication introduces a solid-state technology based on RF GaN/SiC High Electron Mobility Transistors (HEMT) operating at 100 VDC in CW mode, and up to 145 V in pulse mode. In pulse mode, it is an ideal solution for high efficiency using drain modulation as demonstrated in quasistatic mode characterization from 100 V to 145 V. Results based on a 50 mm single die RF transistor are reported here demonstrating 600 W CW at 100 V bias with 80% drain efficiency, and 1 kW at 145 V bias with a pulse width of 100 µs and 10% duty cycle, also with 80% efficiency. Quasi-static drain modulation achieves 3 dB peak power dynamic range with bias modulated from 100 V to 145 V, and 6 dB from 50 V to 145 V. The design employs harmonic tuning techniques for class E, F or F−1power amplifiers to achieve high efficiency and assembly techniques that overcome heat dissipation in such high-power density transistors. These devices and circuits have been designed to operate at 325 and 650 MHz in use at Fermi National Laboratory.