Digital Predistortion Adaptation for Frequency and Gain Shifts
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Solution Overview
Problem
The challenge in wireless device transmit chains is to effectively predistort transmit signals across a wide range of bandwidths and frequency ranges, particularly in 5G NR systems, where high peak-to-power ratio modulation schemes reduce power amplifier efficiency and introduce nonlinear effects, leading to dispersive channels and performance degradation.
Innovation Solution
The implementation of a predistortion system that adapts the predistortion function to compensate for frequency and gain changes by determining frequency offsets and scaling coefficients, allowing the reuse of predistortion functions across different frequency ranges and gain states without additional calibration, using adaptation and inverse adaptation circuitry to ensure accurate signal predistortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a predistortion function is derived during calibration for specific frequency and gain conditions, then predistortion accuracy is improved for those conditions, but the system cannot effectively compensate for frequency offsets or gain changes without additional calibration
Solution Approach 1:
The patent applies parameter changes by detecting frequency offsets and gain differences between calibration and operational conditions, then dynamically adjusting the predistortion function parameters (coefficients, delay values) to compensate for these changes. This allows the system to maintain predistortion accuracy across varying frequency and gain conditions without requiring recalibration for each condition.
Solution Approach 2:
The system transitions from a static predistortion function fixed during calibration to a dynamic function that adapts in real-time based on detected frequency and gain variations. The predistortion function is continuously updated using detected parameters to maintain effectiveness across changing operational conditions.
2Adaptability or versatility
If multiple predistortion functions are stored for different frequency ranges and gain states, then adaptability across conditions is improved, but device complexity and memory requirements increase
Solution Approach 1:
The patent implements a universal predistortion function that can operate across multiple frequency ranges and gain states by incorporating frequency offset and gain difference detection and compensation mechanisms. This single multi-functional approach replaces the need for multiple separate predistortion functions, reducing memory requirements and system complexity while maintaining adaptability.
Solution Approach 2:
The system performs preliminary detection of frequency offsets and gain differences, then uses this information to pre-adjust the predistortion function parameters before applying predistortion. This preliminary action allows a single predistortion function to effectively handle multiple conditions without requiring separate functions for each scenario.
3Productivity
If high peak-to-power ratio modulation schemes are used to increase data rate, then productivity is improved, but power amplifier efficiency decreases and nonlinear effects increase
Solution Approach 1:
The system applies preliminary predistortion to the signal before it reaches the power amplifier to counteract the expected nonlinear effects and efficiency reductions caused by high peak-to-power ratio modulation schemes. This preliminary anti-action compensates for the adverse effects, allowing the system to maintain both high data rates and improved power amplifier efficiency.
Data Source
AI summary
Systems, circuitries, and methods for predistorting a digital signal in a transmit chain based on a predistortion function are provided. A method includes shifting a center frequency of an input signal by an offset to generate an adapted signal; predistorting the adapted signal based on a predistortion function to generate a predistorted adapted signal; reverting the shifting of the center frequency of the predistorted adapted signal by the offset to generate a predistorted signal; and causing transmission of the predistorted signal by a transmit chain.