RF Power Amplifier Predistortion for Nonlinear Distortion Cancellation
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Solution Overview
Problem
Wireless communication devices face inefficiencies due to nonlinear power amplifiers, which cause spectral regrowth and in-band distortion, affecting battery life and power consumption, and existing linearization techniques are inadequate.
Innovation Solution
A digital predistortion method that estimates and compensates for nonlinear characteristics of power amplifiers using polynomial-based models and recursive estimation techniques, aligning and normalizing signal samples to predistort digital signals effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high efficiency power amplifiers are used, then power consumption is reduced and battery life is extended, but nonlinear distortion and spectral regrowth increase
Solution Approach 1:
The patent applies predistortion technique where the transmitted signal is pre-modified before amplification to anticipate and counteract the nonlinear distortion that will be introduced by the power amplifier. This preliminary action ensures that after passing through the nonlinear amplifier, the signal achieves linear amplification with reduced spectral regrowth and in-band distortion, thereby maintaining high efficiency while minimizing harmful nonlinear effects
2Measurement precision
If predistortion training mode is implemented, then accurate alignment of transmit and receive samples is achieved, but system complexity increases
Solution Approach 1:
The patent implements a feedback-based synchronization mechanism where the receiver sends back received signal samples to the transmitter. The transmitter correlates these feedback samples with its original transmit samples to determine timing offset and frequency offset. This feedback loop enables accurate sample alignment and synchronization without requiring complex external synchronization hardware, thereby achieving high measurement precision with manageable system complexity
Data Source
AI summary
Systems and techniques relating to wireless communications are described. A described technique includes generating a digital transmit signal, receiving a digital receive signal, storing signal samples, the signal samples including transmit samples based on the digital transmit signal and receive samples based on the digital receive signal, causing, in a predistortion training mode, the digital receive signal to be based on an amplified analog version of the digital transmit signal, where the amplified analog version is produced by a power amplifier having one or more nonlinear characteristics, determining a synchronization offset value to align the transmit samples with the receive samples, determining one or more power normalization parameter values to normalize a power of the digital receive signal with respect to the digital transmit signal, estimating predistortion parameter values, and using the predistortion parameter values to predistort digital signals to compensate for the one or more nonlinear characteristics of the power amplifier. Estimating predistortion parameter values can include using information comprising the transmit samples, the receive samples, the synchronization offset value, and the one or more power normalization parameter values.