Mixed-Mode Digital Predistortion for Harmonic Distortion Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Power amplifier circuits operating in nonlinear regions face challenges with wideband input signals, leading to increased distortion and noise, particularly when using predistortion compensation, as it becomes difficult to remove distortion terms at carrier frequency harmonics without degrading the input signal.
Innovation Solution
A mixed-mode digital predistortion (DPD) circuit is employed, comprising both linear and nonlinear DPD circuits, which convert complex baseband signals to real signals and back, allowing for separate processing of distortion terms at the carrier frequency and harmonics, using look-up tables and FIR filters to generate pre-distorted signals that minimize noise and distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If predistortion compensation is used to correct distortion terms at carrier frequency, then signal distortion is reduced, but distortion terms at carrier frequency harmonics cannot be effectively removed without degrading the input signal
Solution Approach 1:
The patent divides the predistortion correction into separate segments: a linear DPD circuit handles distortion terms at the carrier frequency, while a nonlinear DPD circuit handles distortion terms at carrier frequency harmonics. This segmentation allows each circuit to be optimized for its specific frequency zone without interfering with the other, resolving the contradiction between correcting carrier frequency distortion and removing harmonic distortion.
2Use of energy by moving object
If a power amplifier operates in nonlinear region to improve efficiency, then power consumption is reduced, but distortion and noise increase
Solution Approach 1:
The patent applies predistortion compensation in advance before the signal enters the nonlinear power amplifier region. By pre-applying the inverse of the expected nonlinear distortion to the input signal, the system enables the power amplifier to operate efficiently in its nonlinear region while the predistortion circuits cancel out the resulting distortion and noise, thus maintaining both efficiency and signal quality.
Data Source
AI summary
Various examples are directed to systems and methods for digital predistortion (DPD). A linear digital predistortion (DPD) circuit may be programmed to generate a pre-distorted signal linear component based at least in part on a complex baseband signal. A nonlinear DPD circuit may be programmed to generate a pre-distorted signal nonlinear component based at least in part on the complex baseband signal. A mixer circuit programmed to generate a pre-distorted signal based at least in part on the pre-distorted signal linear component and the pre-distorted signal nonlinear component.