Digital Pre-Distortion Adaptation with Linear Impairment Subtraction
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Solution Overview
Problem
Current RF amplifiers experience efficiency losses due to non-linear effects, particularly in multilevel modulation schemes like PSK and QAM, leading to gain compression and errors in amplitude and phase, with previous solutions either sacrificing power efficiency or increasing costs with compound semiconductors.
Innovation Solution
Implementing a system with a digital pre-distortion (DPD) module, a power amplifier, a feedback post-processing module, and a linear impairment modeling module to separate and correct non-linear errors, allowing the DPD adaptation engine to update the algorithm and improve digital pre-distortion performance by focusing on non-linear errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If input power to the amplifier is decreased to avoid non-linear effects, then gain compression and distortion are reduced, but power efficiency is lost
Solution Approach 1:
The system applies digital pre-distortion to the input signal before amplification, pre-compensating for the expected non-linear effects. This allows the amplifier to operate at higher input powers for better efficiency while the pre-distorted signal ensures the output remains linear and accurate after passing through the non-linear amplifier.
Solution Approach 2:
The system uses feedback from the amplifier output to continuously monitor and adjust the pre-distortion parameters. By comparing the actual output with the expected output and adjusting the pre-distortion algorithm accordingly, the system maintains signal quality while operating at optimal power efficiency levels.
2Reliability
If compound semiconductors like GaAs are used in RF amplifiers to improve performance, then power efficiency and handling of non-linear effects are improved, but the cost of the amplifier increases
Solution Approach 1:
The system replaces hardware-based solutions (compound semiconductor amplifiers) with a software-based digital pre-distortion system. Instead of using expensive GaAs amplifiers to inherently handle non-linearities, the invention uses digital signal processing algorithms to compensate for non-linear effects, achieving similar performance with standard, lower-cost amplifiers.
3Productivity
If multilevel modulation schemes are used to achieve high speed data transmissions, then data rate is improved, but non-linear effects cause severe performance losses
Solution Approach 1:
The digital pre-distortion system pre-compensates the modulated signal before amplification, accounting for the specific non-linear characteristics of the amplifier. This allows multilevel modulation schemes to operate at higher powers without suffering from gain compression or distortion, maintaining both high data rates and signal accuracy.
Solution Approach 2:
The system dynamically adjusts the pre-distortion parameters based on operating conditions and amplifier characteristics. By changing the pre-distortion algorithm parameters to match the actual amplifier behavior, the system optimizes performance for high-speed multilevel modulation while compensating for non-linear effects.
Data Source
AI summary
Example embodiment of the systems and methods of linear impairment modeling to improve digital pre-distortion adaptation performance includes a DPD module that is modified during each sample by a DPD adaptation engine. A linear impairment modeling module separates the linear and non-linear errors introduced in the power amplifier. The linear impairment model is adjusted during each sample using inputs from the input signal and from a FB post processing module. The linear impairment modeling module removes the linear errors such that the DPD adaptation engine only adapts the DPD module based on the non-linear errors. This increases system stability and allows for the correction of IQ imbalance inside the linear impairment modeling, simplifying the feedback post-processing.