Digital Pre-Distortion Feedback for Linear RF Power Amplifiers
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Solution Overview
Problem
Wireless communication systems face inefficiencies due to power amplifier nonlinearity, leading to signal distortion and high power consumption, especially in low-cost amplifiers, which also exhibit more nonlinearity and result in increased component costs.
Innovation Solution
The implementation of digital pre-distortion (DPD) techniques using a pre-distortion actuator that applies corrections to signals before transmission, employing behavioral models or generalized memory functions, and adaptive engines to dynamically update these models based on feedback, thereby compensating for nonlinearities in power amplifiers and antenna arrays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If power amplifiers are operated below saturation to maintain linearity, then signal distortion is reduced, but power efficiency deteriorates
Solution Approach 1:
The system applies digital pre-distortion to the input signal before amplification, pre-compensating for the anticipated nonlinear distortion. This allows the power amplifier to operate in a more efficient region while the pre-applied correction ensures the final output remains linear and undistorted.
Solution Approach 2:
The system employs feedback mechanisms where the actual output signal is monitored and used to adjust the pre-distortion parameters. This closed-loop approach continuously optimizes the pre-distortion correction to maintain signal linearity while allowing the power amplifier to operate at higher efficiency points.
2Ease of manufacture
If low-cost power amplifiers are used to reduce component costs, then system cost is reduced, but signal nonlinearity increases
Solution Approach 1:
The system creates a digital model or behavioral representation of the power amplifier's nonlinear characteristics through characterization measurements. This model is then used to generate pre-distortion corrections that compensate for the amplifier's imperfections, allowing low-cost amplifiers to achieve high-linearity performance through software-based correction.
Solution Approach 2:
The system dynamically adjusts pre-distortion parameters based on operating conditions such as temperature, input power level, and load impedance. By adapting these parameters in real-time, the system maintains optimal compensation for nonlinearities across varying conditions, enabling low-cost amplifiers to perform reliably.
Data Source
AI summary
A wireless communications system includes a pre-distortion actuator configured to receive a carrier-modulated signal and convert the carrier-modulated signal into an output signal. The system includes one or more antennas configured to receive the output signal and transmit the output signal, one or more power amplifiers electrically coupled between the pre-distortion actuator and the one or more antennas and a receiver configured to receive the output signal over-the-air and generate feedback based on the output signal. The pre-distortion actuator is configured to generate the output signal by applying a correction to the carrier-modulated signal that cancels out nonlinearities associated with the one or more antennas and/or the one or more power amplifiers. The pre-distortion actuator is configured based on the feedback.