A 2-GHz band experiment on efficiency enhancement of a GaN power amplifier using 2nd harmonic injection

This paper presented the basic concept of a 2nd-HI technique that significantly enhances the efficiency of a GaN class-B PA. Experimental results were also presented. In our proposal, efficiency enhancements are achieved when the direct supply current decreases due to clipping in the drain current waveform after 2nd harmonic signal injection. In 2 GHz band experiments, it was confirmed that the direct drain current decreased by injecting a 2nd harmonic signal. The experiments also indicate that there are optimal amplitude and phase values for the injected 2nd harmonic signal which maximize the PA efficiency. As a result of optimizing the 2nd harmonic signal, 72.5 % maximum drain efficiency and 15.2 % efficiency improvement were obtained. In the future, we will investigate the principle of our proposed method in detail using waveform analyses.