Digital Pre-Distorter Structure for Low-Complexity Linearization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing digital compensation methods for non-linear circuits, such as power amplifiers in wireless transmitters, require a large number of parameters and frequent updates to accurately linearize signals, leading to computational complexity and sensitivity to device variations.
Innovation Solution
A digital pre-distorter structure using a balanced polynomial form with a reduced number of parameters, which captures harmonic and intermodulation distortion effects by combining time-filtered versions of linear and non-linear functions, allowing for robust linearization without continuous updating, and utilizing predetermined or condition-specific coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large number of parameters are used in digital pre-distortion to accurately linearize the non-linear circuit, then the linearization accuracy is improved, but the computational complexity increases
Solution Approach 1:
The patent segments the non-linear distortion compensation into separate memoryless polynomial terms (e.g., fundamental frequency, second harmonic, third harmonic, intermodulation terms) that can be independently calculated and combined. This segmentation allows accurate linearization through multiple distortion components while keeping each individual calculation simple and avoiding the need for complex continual updating of a large parameter set.
Solution Approach 2:
The patent changes the parameter representation from a large set of continuously updated coefficients to a smaller set of memoryless polynomial coefficients that can be determined once or updated infrequently. By using predetermined or condition-specific coefficients for each polynomial term, the system achieves accurate linearization with reduced computational complexity and minimal updating requirements.
2Measurement precision
If a large number of parameters are used in digital pre-distortion, then the linearization accuracy is improved, but the sensitivity to device variations increases
Solution Approach 1:
By segmenting the compensation into independent memoryless polynomial terms for different distortion mechanisms (harmonics, intermodulation), the patent reduces the interdependence between parameters. Each term can be independently optimized and is less sensitive to variations in other parameters, improving robustness to device variations while maintaining linearization accuracy.
Solution Approach 2:
The patent transforms the parameter set from continuously updated coefficients to stable memoryless polynomial coefficients that are determined once or updated based on operating conditions. This parameter transformation reduces sensitivity to device variations because each polynomial term represents a specific physical distortion mechanism that can be independently characterized and compensated.
3Measurement precision
If continual updating of parameters is performed to maintain linearization, then the accuracy is maintained, but the operation-time computation complexity increases
Solution Approach 1:
The patent changes from continual parameter updating to using predetermined or condition-specific memoryless polynomial coefficients. The coefficients are determined once during calibration or updated only when operating conditions change significantly, eliminating the need for continuous computation during normal operation and dramatically improving real-time computation efficiency while maintaining linearization accuracy.
Solution Approach 2:
The patent performs the complex parameter determination in advance during calibration or setup, storing the resulting memoryless polynomial coefficients for direct use during operation. This preliminary action eliminates the need for continual updating during real-time signal processing, as the pre-determined coefficients directly compensate for non-linearities without requiring ongoing computation.
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An approach to digital compensation uses a particular structure for a digital pre-distorter (DPD) which acts as a relatively accurate pre-inverse of a non-linear circuit (e.g., a non linear transmit chain involving digital-to-analog converter (DAC), lowpass filter, modulator, bandpass filter, and power amplifier) while making use of a relatively small number of parameters that characterize the non-linearity and/or parameters that provide accurate linearization without requiring continual updating.