Power Amplifier Linearisation Through Low-Frequency Feedback

This paper outlines the development of a novel linearisation technique that has been shown to achieve significant reduction in third-order intermodulation distortion. Power Series analysis is used to show how second-order low-frequency components can be used to reduce in-band distortion, with CAD simulations presented to demonstrate the application of the technique, including its tolerance to non-optimal feedback phase and amplitude response. To verify the simulation results, a single-stage PA was constructed and linearised by the application of a second-order low-frequency signal. With a two-tone input signal the achievable reduction in third-order intermodulation distortion was found to be 15dB in practice and 15.5dB in simulation.