Digital Predistortion of Nonlinear RF Power Amplifier

The process of Digital Predistortion for Nonlinear RF Power Amplifiers with Memory Effects represents a critical linearization technique in wireless communication systems. The provided MATLAB code implements a comprehensive simulation framework for linearizing Class AB nonlinear HPAs exhibiting memory effects. The implementation employs a memory polynomial predistorter to model both nonlinear distortion and memory effects in the HPA. The simulation architecture comprises three key algorithmic components: 1. Analog Imperfection Compensation for Direct Upconversion Transmitters: The code includes IQ imbalance compensation and DC offset correction algorithms to mitigate transmitter-side impairments before DPD application. 2. Memory Polynomial Predistorter Design: The core DPD implementation uses least-squares estimation to compute memory polynomial coefficients, where the predistorter structure incorporates both instantaneous nonlinearities and memory effects through cross-terms between current and past input samples. 3. Performance Evaluation Metrics: The simulation quantifies linearization performance using standardized measurements including Error Vector Magnitude (EVM) for constellation accuracy, Power Spectral Density (PSD) for spectral regrowth analysis, and Signal-to-Noise Ratio (SNR) for overall system quality assessment. By implementing this structured approach, the DPD system effectively cancels HPA-induced distortion, demonstrating significant improvements in signal fidelity and spectral efficiency for enhanced wireless communication performance. The code provides configurable parameters for polynomial order, memory depth, and training sequence length to accommodate various amplifier characteristics.