Linearization and efficiency enhancement of the RF power amplifier by the even-order nonlinear signal injection

In this paper a broadband RF power amplifier operating at frequency range 0.75 GHz to 1.25 GHz is linearized by the even-order nonlinear signals at frequencies around the second harmonics that are inserted at the amplifier transistor gate and drain throughout the broadband matching circuits that provide high amplifier efficiency as well as adequate power level of the injected signal for the linearization. The effects of the transistor input (gate) second harmonic impedance on the amplifier efficiency is examined in addition to the analysis of the influence of the output (drain) second harmonic impedance performed earlier. The amplifier linearization is carried out for two-tone test characterized by different frequency interval between signals up to 100 MHz for various signal power levels as well as for WCDMA digitally modulated signal.