Broadband High-Efficiency Continuous Class-F/F^-1 Power Amplifiers with Active Second Harmonic Injection Technique

In this paper, focusing on the power amplifier (PA) in ultra low power RF circuits and systems, a novel circuit topology with active second harmonic injection technique is derived and analyzed for the wideband high-efficiency continuous class-F/F^-1 (CCF/F^-1) modes for the first time. By introducing an auxiliary PA operated at the second harmonic frequency of the desired band, the optimal phase shift parameter between the drain voltage and current of the CCF/F-¹ PA can be selected properly, leading to the improvement of the total efficiency and output power. Calculated results show that, with the proposed structure, the maximum output powers are 1.323 and 1.319 times larger than those in the traditional CCF and CCF^-1 modes, and the maximum drain efficiencies are increased to 98.16% and 93.16%, respectively. Finally, in order to verify the validity of the proposed circuit, a frequency-domain simulation has been presented. It is shown that the difference of intrinsic voltage and current waveforms, drain efficiency as well as output power between the results of theory and simulation is very small.