High Efficiency HBT Power Amplifier Utilizing Optimum Phase of Second Harmonic Source Impedance

A new type of source matching for improving the efficiency of an inverse Class-F (Class-F ^-1) amplifier is presented. The squared waveform voltage is generated by adjusting the phase of finite second harmonic voltage shift. To verify the superior performance of the proposed technique, two-stage HBT PAs with different types of source matching were fabricated using a commercial process. The proposed PA delivers approximately 4.8% improvement in efficiency over a conventional PA. The peak output power is enhanced by 2 dB.