Low-Power, Adaptive Digital Pre-Distortion Linearization of Ultra-Wideband RF Power Amplifiers

This paper presents a fully adaptive digital predistortion using a multi-dimensional nonlinear model that is implemented in hardware without the use of any digital multipliers and operates at very wide instantaneous bandwidths (>1 GHz instantaneous bandwidth). This multi-dimensional compensator effectively mitigates linear and nonlinear distortion in RF power amplifiers by modeling the state of the device by tracking multiple functions of the input, which can include: the present input signal value; delayed values of the input (for memory effects); derivatives of the input (including higher order derivatives); integration of the input (including higher order integrals); signal statistics (e.g., mean, variance); current power level (RMS or peak); and polynomial functions of the input. The processing is implemented with memory instead of digital multipliers for low-power applications. It is calibrated using simple arithmetic operations that can be completed with low processing requirements and very quickly to track parameters that rapidly change over time, temperature, and power level such as in frequency-hopping systems. The approach has been demonstrated in realtime hardware providing 15-30 dB improvement in distortion.