Design of a Class-B Power Amplifier at 2.4 GHz with Improved Harmonic Suppression

This paper presents a highly efficient class-B power amplifier at 2.4 GHz. Efficiency enhancement is achieved by terminating the input and output of the amplifier with its optimum source and load impedances, obtained from load-pull analysis and suppressing first six harmonics. The harmonic suppression is obtained by a compact lowpass filter based on stepped impedance resonators with multiple transmission zeros. A prototype amplifier is fabricated that provides a measured power added efficiency of 53.1% with a gain of 14.18 dB.