Novel MMIC Power Amplifier Linearization Utilizing Input Reflected Nonlinearity

This paper introduces a novel method to generate an auxiliary third-order intermodulation (IM3) signal, which can be used in the linearization of power amplifiers (PAs) by canceling the output IM3 power. This auxiliary signal is simply achieved by exploiting the input reflected power of the main device, rather than obtained by conventional methods as driving a highly nonlinear device or subtracting the fundamental power from the output signal. It is demonstrated that substantial IM3 power can be reflected to the source with little reflected fundamental power under some input matching conditions of the device, and this feature can be utilized in the design of monolithic microwave integrated circuits (MMICs) targeting excellent linearity. A 25-GHz pHEMT power amplifier is designed and fabricated to exemplify the proposed technique. With the linearization, the OIP3 of the proposed PA increases by 14 dB from 25 to 39 dBm, and the output power enhances significantly, from 5 to 14 dBm with -40-dBc IM3 distortion and from 9 to 14 dBm with -40-dBc adjacent channel power ratio.