Adaptive Digital Predistortion for Varying RF Operating Conditions
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Solution Overview
Problem
Conventional digital predistortion (DPD) techniques face challenges in adapting quickly to varying operating conditions, such as rapid changes in spectral localization, power levels, temperature, and Voltage Standing Wave Ratio (VSWR), which affect the non-linear characteristics of power amplifiers used in wireless communication devices, leading to reduced accuracy and robustness.
Innovation Solution
The implementation of adaptive digital predistortion systems that collect and process data samples based on variety metrics to select a subset of data records with high distinguishability, deriving an expanded set of basis functions from initial ones, and configuring the digital predistorter with computed parameters to adapt to changing operating conditions, including temperature, power supply voltage, and VSWR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional digital predistortion adaptation processes are used, then the system can compensate for nonlinear characteristics of power amplifiers, but the computation effort is substantial which limits the number and speed at which DPD coefficients can be derived, reducing predistortion accuracy and robustness
Solution Approach 1:
The patent segments the operating conditions into discrete clusters (e.g., different temperature ranges, power levels, VSWR conditions) and pre-computes DPD coefficients for each cluster. This segmentation allows the system to avoid full-complexity computations during runtime, instead selecting pre-computed coefficients based on current operating conditions, thereby reducing real-time computational effort while maintaining accuracy.
Solution Approach 2:
The system performs preliminary computation of DPD coefficients offline or during calibration phases for various operating conditions, storing these pre-computed coefficients for rapid retrieval during operation. This preliminary action eliminates the need for complex real-time computations during actual transmission, resolving the contradiction between accuracy and computational complexity.
2Adaptability or versatility
If DPD coefficients are updated frequently to adapt to varying operating conditions, then predistortion performance improves, but the computational load increases and may exceed processing capabilities
Solution Approach 1:
The patent implements a dynamic coefficient selection mechanism that adapts the DPD parameters based on monitored operating conditions (temperature, power level, VSWR). When operating conditions change significantly, the system dynamically switches to different pre-computed coefficient sets. This dynamic approach enables fast adaptation without triggering full recomputation, balancing adaptability with computational constraints.
Solution Approach 2:
The system changes key parameters (temperature thresholds, power levels, VSWR ranges) that define operating condition clusters. By monitoring these parameter changes and switching between pre-computed coefficient sets corresponding to different parameter ranges, the system achieves rapid adaptation to varying conditions without the computational burden of continuous coefficient recalculation.
3Adaptability or versatility
If the digital predistorter uses a fixed set of basis functions, then the system is simpler to implement, but it cannot adapt to rapid changes in operating conditions such as spectral localization, power levels, temperature, and VSWR
Solution Approach 1:
The patent develops a universal DPD framework with a standardized set of basis functions that can handle multiple operating conditions (different frequencies, power levels, temperatures, VSWR values) through a unified model. This universal approach allows the same basis function set to serve multiple purposes across varying conditions, reducing overall system complexity while maintaining adaptability through parameter adjustments rather than requiring separate models for each condition.
Solution Approach 2:
The system maintains a fixed basis function structure but adapts to varying operating conditions by changing the parameters (coefficients) that weight these basis functions. Different operating conditions (spectral localization, power levels, temperature, VSWR) are accommodated by selecting or adjusting coefficient values rather than changing the fundamental basis function set, thus achieving adaptability without proportionally increasing system complexity.
Data Source
AI summary
Disclosed are implementations for digital predistortion of signals provided to a radio frequency (RF) transmission path configured to transmit radio signals in a plurality of subbands within a spectral range, including a method that includes configuring a digital predistorter for predistorting signals comprising arbitrary spectral content within the spectral range. The configuring includes acquiring data samples representing operation of the RF transmission path to transmit radio signals in different subbands, each sample including a digital input signal representing spectral content concentrated in a respective subband, and updating parameters of the digital predistorter according to the acquired data samples to mitigate non-linear characteristics of the RF transmission path. The method further includes receiving a further input signal representing spectral content in a particular subband within the spectral range, and using the configured predistorter to process the further input signal to yield a predistorted signal for providing to the RF transmission path.