Efficient linear supply-modulated PA with harmonic injection

This paper discusses the concept of partial supply modulation with harmonic injection at the output of a PA, resulting in constant high efficiency and linearity over a wide range of output power levels. Nonlinear simulations for the TriQuint TGF2023-01 6-W GaN device are validated with a proof-of-concept PA biased in class-AB mode at 2.45 GHz. Efficiencies in the range of 62-76% are achieved for a ≤ 7 dB variation in the output power. The corresponding range of drain voltage is 10-27V and injected harmonic power range is -33 to -10 dBc w.r.t. fundamental output power. This high efficiency amplifier simultaneously achieves high linearity. Simulated and measured third harmonic shows a ≥ 15 dB reduction as compared to a PA with no harmonic injection. It is also shown that simulated two-tone IMD3 follow a similar trend.