Predistortion Phase Rotation for Stable Coefficient Updates
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Solution Overview
Problem
Existing distortion compensation systems face challenges in achieving stable distortion compensation due to clock jitter and phase variations between reference and feedback signals, leading to unstable distortion compensation coefficients and increased adjacent channel leak power.
Innovation Solution
A simplified distortion compensation apparatus that includes a correlation calculation section to determine the real and imaginary parts of the correlation between reference and feedback signals, a phase rotation section to compensate for phase deviations, and a storage system to update distortion compensation coefficients based on phase information, with intermittent control to manage phase correction and coefficient updates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If distortion compensation is performed using adaptive algorithms with feedback signals, then nonlinear distortion is reduced and adjacent channel leak power decreases, but clock jitter and phase variations cause instability in distortion compensation coefficients
Solution Approach 1:
A phase rotation section is introduced as an intermediary component between the feedback signal path and the distortion compensation coefficient calculation. This phase rotation section specifically compensates for phase variations caused by clock jitter, thereby stabilizing the distortion compensation coefficients without affecting the overall distortion compensation performance.
Solution Approach 2:
The patent utilizes feedback signals from the power amplifier output, but implements a phase correction mechanism based on correlation calculation between reference and feedback signals. This feedback-based phase correction stabilizes the distortion compensation coefficients against clock jitter and phase variations while maintaining the adaptive distortion compensation functionality.
2Object-generated harmful factors
If the linear region of the power amplifier is widened to reduce leak power, then adjacent channel interference decreases, but apparatus cost and size increase due to requiring larger capacity amplifiers
Solution Approach 1:
The distortion compensation apparatus applies predistortion to the input signal before amplification, pre-compensating for the nonlinear characteristics of the power amplifier. This allows the amplifier to operate in its nonlinear region while still achieving linear output, thereby reducing adjacent channel leak power without requiring larger capacity amplifiers.
Solution Approach 2:
The patent dynamically adjusts distortion compensation coefficients based on the operating conditions and feedback signals. By changing the compensation parameters adaptively, the system optimizes the trade-off between leak power reduction and amplifier utilization, avoiding the need for oversized amplifiers while maintaining low adjacent channel interference.
3Manufacturing precision
If distortion compensation coefficients are updated continuously to improve compensation accuracy, then nonlinear distortion reduction improves, but calculation time and processing complexity increase
Solution Approach 1:
The distortion compensation coefficients are updated periodically rather than continuously, based on correlation calculation results between reference and feedback signals. This periodic update mechanism maintains sufficient compensation accuracy while significantly reducing the calculation time and processing complexity compared to continuous updates.
Data Source
AI summary
A distortion compensation apparatus is provided to restrain an increased calculation time caused by a large amount of calculation required for obtaining a phase variation amount for compensation from the correlation. The distortion compensation apparatus includes an update calculation section calculating a distortion compensation coefficient by use of an adaptive algorithm; a distortion compensation section performing distortion compensation to the transmission signal, based on the distortion compensation coefficient being read out from the distortion compensation coefficient storage; a correlation calculation section calculating a real part of correlation and an imaginary part of correlation of each the reference signal and the feedback signal; and a phase rotation section compensating a relative phase deviation between the reference signal and the feedback signal, based on the real part of correlation and the imaginary part of correlation calculated by the correlation calculation section, wherein the update calculation section calculates a distortion compensation coefficient using the post-compensation signal.