부산대학교 도서관

In this article, the theory and design of high-efficiency broadband continuous class-B/J power amplifiers (PAs) with active second harmonic injection technique have been presented. By injecting the second harmonic component generated by the auxiliary PA, the optimal phase shift parameter $\alpha $ between the drain voltage and current can be selected properly, leading to an efficiency and power improvement of the conventional class-B/J PA. Detailed design guidelines and step-by-step procedure are also suggested. To verify the feasibility of the proposed circuit, a wideband PA operated from 1.1 to 1.7 GHz (fractional bandwidth of 42.9%) has been designed and fabricated. Experimental results show an output power of 40.9–42.6 dBm, drain efficiency of 70.0%–80.9%, and average efficiency (AE) of 74.4%. To the best of our knowledge, this is the highest AE of class-B/J PAs over such bandwidth.