Predistortion Circuit Using Orthogonal Basis Functions for PA Linearity
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Solution Overview
Problem
Digital predistortion technologies for power amplifiers suffer from slow convergence and low numerical stability due to high correlation among matrix columns, which affects the linearity and efficiency of power amplifiers in wireless communication systems.
Innovation Solution
A circuit and method that utilize a digital predistorter, DAC, PA, attenuator, ADC, timing synchronizer, statistics generator, and orthogonal basis function generator to generate and update predistortion coefficients, employing normalized orthogonal basis functions to reduce correlation and improve stability, thereby enhancing the linearity of power amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If digital predistortion technology based on common digital polynomial is used, then the power amplifier linearity is improved, but the convergence speed is slow and numerical stability is low
Solution Approach 1:
The patent changes the basis functions from common digital polynomial to normalized orthogonal basis functions. This parameter change in the mathematical model transforms the highly correlated matrix columns into orthogonal columns with low correlation, thereby improving both convergence speed and numerical stability while maintaining power amplifier linearity improvement.
Solution Approach 2:
The patent substitutes the traditional polynomial-based predistortion mechanism with an orthogonal basis function-based mechanism. This substitution replaces the problematic high-correlation matrix structure with a well-conditioned orthogonal matrix structure, enabling faster convergence and better numerical stability without sacrificing linearity correction capability.
2Reliability
If digital predistortion technology based on common digital polynomial is used, then the power amplifier linearity is improved, but the numerical stability is low
Solution Approach 1:
The patent changes the basis functions from common digital polynomial to normalized orthogonal basis functions. This parameter change in the mathematical model transforms the highly correlated matrix columns into orthogonal columns with low correlation, thereby improving both convergence speed and numerical stability while maintaining power amplifier linearity improvement.
Solution Approach 2:
The patent substitutes the traditional polynomial-based predistortion mechanism with an orthogonal basis function-based mechanism. This substitution replaces the problematic high-correlation matrix structure with a well-conditioned orthogonal matrix structure, enabling faster convergence and better numerical stability without sacrificing linearity correction capability.
Data Source
AI summary
A circuit for predistortion, comprising a digital predistorter configured to generate a modified digital signal by modifying an input baseband signal with a predistortion coefficient; a DAC configured to generate an analog signal by converting the modified digital signal; a PA configured to generate an amplified signal by amplifying the analog signal; an attenuator configured to generate an attenuated signal by attenuating the amplified signal; an ADC configured to generate a attenuated digital signal; a timing synchronizer configured to generate a synchronized amplified signal by synchronizing the attenuated digital signal with the modified digital signal; a statistics generator configured to generate a probability density function of a plurality of samples of the input baseband signal; an orthogonal basis function generator configured to generate a set of normalized orthogonal basis functions; a predistortion coefficient training circuit configured to generate an updated predistortion coefficient.