Digital Predistortion Adaptation for Varying PA Operating Conditions
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Solution Overview
Problem
Conventional digital predistortion (DPD) systems face challenges in adapting quickly to varying operating conditions, such as changes in spectral localization, average power, 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 techniques that include collecting and selecting data records based on variety metrics to compute digital predistortion parameters, using an expanded set of basis functions derived from operating conditions, and optimizing parameters to mitigate non-linear distortions across a wideband RF spectral range.
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, adversely affecting predistortion accuracy and robustness
Solution Approach 1:
The patent segments the wideband RF spectral range into multiple subbands and processes each subband separately. This division reduces the computational complexity of adapting DPD coefficients for the entire bandwidth while maintaining accuracy across different operating conditions. Each subband can be adapted independently, allowing faster coefficient derivation without sacrificing overall predistortion precision.
Solution Approach 2:
The patent implements dynamic adaptation of DPD coefficients based on varying operating conditions such as spectral localization, average power, temperature, and VSWR. The system continuously monitors these parameters and updates coefficients in real-time, enabling the predistortion system to maintain high accuracy despite changing environmental conditions while managing computational load through efficient adaptation algorithms.
2Adaptability or versatility
If the UE transmitter adjusts output power by changing DC supply voltage and operates in varying frequency ranges, then the system can adapt to different transmission requirements, but the characteristics of the transmit chain change rapidly, requiring the DPD to adapt quickly to maintain performance
Solution Approach 1:
The patent performs preliminary adaptation of DPD coefficients for different subbands before actual transmission occurs. By pre-computing and storing adaptation parameters for various operating conditions including different power levels, frequencies, and environmental parameters, the system can quickly switch to appropriate coefficients when conditions change, eliminating the need for lengthy real-time computation during rapid transitions.
Solution Approach 2:
The patent changes the parameters used for DPD adaptation to include specific operating conditions such as DC supply voltage levels, spectral localization, average power, temperature, and VSWR. By incorporating these parameters into the adaptation process, the system can predictively adjust coefficients based on anticipated operating condition changes, achieving faster adaptation to varying transmission requirements.
3Reliability
If digital predistortion is implemented to compensate for nonlinear distortion as output power approaches maximum rated output, then the system can achieve linear amplification with reduced nonlinear distortion, but the computation effort limits the number and speed of DPD coefficient derivation
Solution Approach 1:
The patent divides the power amplifier operation into multiple subbands and derives DPD coefficients for each subband separately. This segmentation allows the system to maintain high linearity across the entire operating range by optimizing coefficients for specific power levels and frequency ranges, while reducing the overall computational burden by processing smaller subband datasets in parallel rather than computing a single comprehensive coefficient set.
Data Source
AI summary
Disclosed are digital predistortion implementations, including a method that includes obtaining a first set of digital predistortion (DPD) non-linear functions for controlling operation of a digital predistorter of a wireless device operating on a received at least one input signal directed to a power amplification system comprising a transmit chain with at least one power amplifier that produces output with non-linear distortions. The method further includes determining an expanded set of DPD non-linear functions comprising the first set of DPD non-linear functions and additional one or more sets of DPD non-linear functions derived based on the first set of DPD non-linear functions and on operating condition parameters associated with operation of the wireless device, and configuring the digital predistorter with DPD coefficients determined for the expanded set of the DPD non-linear functions based on observed samples of the transmit chain responsive to the at least one input signal.