Design of Power Amplifier Operating on Wide Input Power Range Based on Impedance Mismatch Evaluation Model

Microwave power transmission (MPT) is one of the most promising techniques for long-distance wireless power transmission. Power amplifier (PA) is an essential part of MPT. However, the biggest problem existing in PA is the serious efficiency loss at low input power, meaning that it cannot work efficiently on a wide input power range. To solve the problem, this paper proposes a new impedance design method and establishes a simplified impedance mismatch evaluation model with only two parameters to precisely estimate the severity of impedance mismatch loss (SIML). This model can be readily utilized under any matching condition and accurately depict the impedance-efficiency characteristics with the impedance obtained by load pull. Based on the model, the impedance design strategy for maximum efficiency is derived. A 5.8GHz/20W high efficiency harmonic controlled PA operating on a wide input power range is constructed to verify the proposed model and impedance design strategy.