Walsh-Domain Predistortion for Power Amplifier Nonlinearity

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Solution Overview

Problem

Existing digital predistortion techniques for power amplifiers in radiofrequency signals require high computational load, making them difficult to implement in baseband, intermediate frequency, and radiofrequency applications, and fail to efficiently adapt to changes in power amplifier behavior over time.

Innovation Solution

A predistortion method using a Walsh transform and Volterra series in the Walsh domain to reduce computational load, allowing implementation in baseband, intermediate frequency, and radiofrequency applications, and adapt to power amplifier variations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional digital predistortion techniques are used to compensate for power amplifier non-linearities, then the linearity of the transmitted signal is improved, but the computational load becomes excessively high

Engineering Contradiction:

Improvesignal linearityVSAvoidcomputational load

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent changes the domain parameters by transforming the predistortion problem from the time domain to the Walsh domain. This parameter transformation allows the use of Walsh-Hadamard transforms and dyadic convolutions, which reduce the computational complexity from O(N²) to O(N log N), thereby resolving the contradiction between maintaining signal linearity and reducing computational load

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent substitutes conventional time-domain convolution operations with Walsh-domain dyadic convolutions. This substitution replaces the computationally intensive mechanical process of time-domain filtering with an equivalent but more efficient Walsh-domain operation, achieving the same predistortion effect with reduced computational requirements

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Use of energy by moving object

If power amplifiers operate in the non-linear region to achieve high energy efficiency, then energy consumption is reduced, but signal distortion increases

Engineering Contradiction:

Improveenergy efficiencyVSAvoidsignal quality

Core Design Contradiction:

Use of energy by moving objectVSManufacturing precision

Solution Approach 1:

The patent applies preliminary action by pre-distorting the signal in the Walsh domain before it enters the power amplifier. The predistortion block预先 applies the inverse of the amplifier's non-linear transfer function, so that when the signal passes through the non-linear amplifier, the distortions cancel out and the output remains linear, allowing operation in the efficient non-linear region while maintaining signal quality

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent converts the harmful non-linear distortion into a benefit by deliberately pre-applying the opposite distortion. The predistortion block intentionally distorts the signal in a controlled manner that compensates for the amplifier's non-linearity, turning what would be harmful distortion into a corrective mechanism that enables efficient non-linear operation while maintaining output linearity

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Measurement precision

If power amplifier parameters are updated frequently to track behavioral changes over time, then compensation accuracy is improved, but device complexity increases

Engineering Contradiction:

Improvecompensation accuracyVSAvoidmodel update complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent implements feedback by continuously monitoring the power amplifier's output and using this information to update the predistortion model parameters. The system measures the actual amplifier behavior and adjusts the Walsh-domain predistortion coefficients accordingly, maintaining high compensation accuracy while the structured feedback loop manages complexity through systematic parameter adaptation

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS20260025108A1Method for predistorting an input signal in order to compensate for the effect of a non-linear transfer function of a power amplifier, corresponding computer program products and devices

Publication Date: 2026.01.22 UNIVERSITE DE BORDEAUX

AI summary

A method for predistorting an input signal with a view to compensating for the effect, on a radiofrequency signal generated from the input signal, of a non-linear transfer function of a power amplifier configured to amplify the radiofrequency signal. The method includes: carrying out a Walsh transform of a series of M terms dependent on temporal samples of the input signal delivering sequential components of a corresponding transformed series; calculating a sum of a plurality of operands resulting from the product between, a piece of data dependent on at least one element of a transformed series and a corresponding predistortion coefficient, delivering a corresponding sequential component of a predistorted transformed input signal: and carrying out an inverse Walsh transform of the sequential components of the predistorted transformed input signal, delivering an output signal for the generation of the radiofrequency signal.