Design of harmonic processing circuit for microwave GaN-HEMT power amplifier

By processing harmonics, high-efficiency microwave GaN power amplifier can be realized. However, due to parasitic elements of transistor and package, performance of actual amplifier cannot be that of ideal, especially for high power transistor. Thus, it is difficult to obtain high efficiency by ideal harmonic processing, such as class-F. Optimum harmonic reflection phases, which were different from those of class-F or inverse class-F, were calculated by harmonic balance analysis using non-linear transistor model developed by the authors. By using the model, experimental high-efficiency power amplifiers were designed and fabricated. Measured results were compared with simulated ones. As a result, effectiveness of the design method for harmonic processing amplifier using nonlinear model was confirmed.