Predistortion Coefficient Update for Signal-Level Distortion Control
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Solution Overview
Problem
Conventional distortion compensation systems face challenges in effectively managing the step size parameter for updating distortion compensation coefficients, leading to issues such as divergence at high transmission signal levels and inadequate updates at low signal levels, which affects the accuracy and reliability of nonlinear distortion compensation in radio communication systems.
Innovation Solution
The proposed distortion compensation apparatus includes a control mechanism that adaptively adjusts the step size parameter based on the integral value of the transmission signal, using a memory to store parameter values corresponding to signal levels, and optionally employs a fast Fourier transform circuit to optimize noise reduction, ensuring the step size parameter is modified to prevent divergence and ensure accurate coefficient updates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed step size parameter is used for updating distortion compensation coefficients, then the system structure remains simple, but divergence occurs at high transmission signal levels and inadequate updates occur at low signal levels
Solution Approach 1:
The step size parameter is changed from a fixed value to a dynamically adjustable parameter that varies according to the transmission signal level. The control mechanism adapts the step size parameter in real-time based on signal conditions, making the system flexible and responsive to changing operating conditions, thereby preventing both divergence and inadequate updates.
Solution Approach 2:
The invention changes the parameter value of the step size parameter based on the transmission signal level. When the transmission signal level is high, a smaller step size parameter is used to prevent divergence. When the transmission signal level is low, a larger step size parameter is used to ensure adequate updates. This parameter adaptation resolves the contradiction between reliability and complexity.
2Reliability
If the step size parameter is increased to ensure updates at low signal levels, then update adequacy improves, but divergence occurs at high signal levels
Solution Approach 1:
The step size parameter is dynamically adjusted based on the transmission signal level to maintain both update adequacy and coefficient stability. At low signal levels, the parameter is increased to ensure adequate updates. At high signal levels, the parameter is decreased to prevent divergence and maintain stability.
Solution Approach 2:
The invention implements parameter changes in the step size parameter according to signal level conditions. This allows the system to optimize between update adequacy and stability by selecting appropriate parameter values for different operating conditions, resolving the contradiction between these two requirements.
3Stability of the object's composition
If the step size parameter is decreased to prevent divergence at high signal levels, then coefficient stability improves, but inadequate updates occur at low signal levels
Solution Approach 1:
The system dynamically adjusts the step size parameter based on transmission signal level to maintain both stability and accuracy. At high signal levels, a smaller parameter value ensures stability. At low signal levels, a larger parameter value ensures adequate updates and maintains accuracy.
Solution Approach 2:
The invention employs parameter changes in the step size parameter according to operating conditions. This allows the system to achieve both coefficient stability and distortion compensation accuracy by adapting the parameter value to the current signal level, resolving the contradiction between these two performance aspects.
Data Source
AI summary
A step size parameter μ is adaptively varied when a distortion compensation coefficient is calculated in a distortion compensation apparatus, relation between transmission signal level and step size parameter μ is considered. The distortion compensation apparatus includes a memory storing distortion compensation coefficient in a designated write address, and outputting distortion compensation coefficient being stored in a designated readout address; a predistortion section performing distortion compensation processing onto a transmission signal, using the distortion compensation coefficient being output from memory; and a distortion compensation section calculating an update value of distortion compensation coefficient, based on error component existent between transmission signal before distortion compensation processing and transmission signal after being amplified by an amplifier. Further, the distortion compensation section modifies magnitude of step size parameter determining degree of effect of error component produced on the update value, when calculating the update value of the distortion compensation coefficient.