High efficiency microwave harmonic reaction amplifier

The principle of operation of the high-efficiency harmonic reaction amplifier (HRA) is clarified. The HRA is basically constructed of a pair of power FETs. The technical originality lies in the provision of an interconnecting circuit for providing an additional second-harmonic transmission path between the two FETs. These paths are designed to have impedance characteristics matched to the FETs´ output impedances in the fundamental frequency band and in the second-harmonic frequency band, respectively. This additional circuit realizes the efficient and stable switching-mode operation required for highly efficient microwave power amplification. Theoretical analysis results indicate that a drain efficiency of 86% is available for an ideal HRA of purely class-B operation. Experiments on a miniaturized 2-GHz 5-W HRA module were conducted to verify analysis results. A power-added efficiency of over 70% was achieved confirming that the HRA can be applied practically to microwave power amplifiers. A HRA capability for high-efficiency operation as a linear amplifier under class-AB conditions is also shown by the experiments.<>