RF Power Amplifier Predistortion With Quadrature Error Correction
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Solution Overview
Problem
Modern wireless transceivers face challenges in balancing the linearity and efficiency of RF amplifiers, particularly with spectrally efficient signals causing in-band distortions, and direct-conversion transmitters are sensitive to gain imbalance and phase errors, requiring complex monitoring and correction systems.
Innovation Solution
A power amplification system incorporating a digital predistortion unit and quadrature modulation correction units, implemented using FPGA devices, to estimate and correct non-linear effects and modulation errors, with intermediate-frequency conversion to filter out spurious signals and optimize bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If an efficient but non-linear power amplifier is used to improve energy efficiency, then power efficiency is improved, but linearity deteriorates causing in-band distortions and out-of-band spectral regrowth
Solution Approach 1:
The patent applies digital predistortion that pre-compensates the modulated signal before it reaches the power amplifier. The predistortion unit calculates correction coefficients based on monitored amplifier characteristics and applies inverse non-linearity to the signal in advance, so that the amplifier's non-linear effects are cancelled out, maintaining both efficiency and linearity
Solution Approach 2:
The patent implements a monitoring system that continuously observes the power amplifier's output signal and feeds this information back to the predistortion unit. This feedback loop enables real-time adaptation of predistortion coefficients to compensate for temperature variations, component aging, and other dynamic changes in amplifier characteristics
2Manufacturing precision
If digital predistortion and quadrature modulation correction are added to maintain perfect system performance, then linearity and spectral efficiency are improved, but device complexity increases
Solution Approach 1:
The patent combines the digital predistortion function and quadrature modulation correction function into a single integrated unit. Both correction mechanisms share common components including the monitoring system, coefficient calculation algorithms, and signal processing pathways, reducing overall system complexity while maintaining both linearity and spectral efficiency
Solution Approach 2:
The monitoring system serves multiple functions simultaneously: it monitors the power amplifier's non-linearity for predistortion purposes, monitors quadrature modulation errors for correction purposes, and adapts both correction mechanisms. This multi-functional approach reduces the need for separate dedicated systems for each correction type
Data Source
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AI summary
Power amplification system (S) for radio frequency communications, comprising a input port (IN) of an input radio frequency signal (RF IN), an output port (OUT) of an output radio frequency signal (RF OUT); a digital predistortion unit (DPD) operatively interposed between the input port (IN) and the output port (OUT) and a quadrature modulation correction means (QMC IN, QMC OUT, QMC OBS) operatively interposed between the digital predistortion unit (DPD) and between at least one of the input port (IN) and the output port (OUT).