Quadrature Receiver Coefficient Control for Stable I/Q Mismatch Correction
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Solution Overview
Problem
Low-IF quadrature receivers face challenges in compensating for in-phase/quadrature (I/Q) mismatch, leading to image rejection ratio (IRR) issues, with existing methods like LMS adaptation introducing artifacts and instability, especially during fast convergence or re-convergence.
Innovation Solution
A quadrature receiver architecture incorporating a correction engine, adaptation engine, and coefficient controller to adaptively compensate for I/Q mismatch by selectively updating filter coefficients based on performance criteria and timing-driven logic, ensuring stable and effective I/Q mismatch compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If LMS adaptation is used to compensate for I/Q mismatch, then I/Q mismatch compensation is achieved, but artifacts and instability are introduced during fast convergence or re-convergence
Solution Approach 1:
The patent segments the adaptation process into distinct phases: a convergence phase where the filter coefficient is continuously adapted to achieve I/Q mismatch compensation, and a data burst phase where the filter coefficient is held constant to avoid instability. This segmentation allows the system to achieve precise I/Q mismatch compensation during calibration while maintaining stability during actual data reception.
Solution Approach 2:
The patent implements periodic re-convergence of the filter coefficient at predetermined intervals (e.g., every N data bursts) rather than continuous adaptation. This periodic action allows the system to periodically update the I/Q mismatch compensation while maintaining stability during data bursts, preventing the artifacts and instability associated with continuous adaptation during fast convergence.
2Measurement precision
If continuous adaptation of filter coefficient is performed, then I/Q mismatch compensation is maintained, but computational complexity and processing overhead increase
Solution Approach 1:
The patent reduces computational complexity by performing filter coefficient adaptation periodically rather than continuously. The adaptation engine updates the filter coefficient only at predetermined intervals (e.g., every N data bursts) or based on specific triggering events, significantly reducing the computational load compared to continuous adaptation while maintaining adequate I/Q mismatch compensation accuracy.
Solution Approach 2:
The patent performs I/Q mismatch compensation calibration in advance during initialization or idle periods, establishing the filter coefficient before actual data reception begins. This preliminary action separates the computationally intensive adaptation process from the data processing path, reducing real-time processing complexity while maintaining compensation accuracy.
3Adaptability or versatility
If filter coefficient is updated frequently, then I/Q mismatch compensation adapts to changing conditions, but instability and artifacts increase during data bursts
Solution Approach 1:
The patent segments the operation into distinct modes: a calibration mode where the filter coefficient is adapted to track changing I/Q mismatch conditions, and a data reception mode where the coefficient is held constant to ensure stability. This segmentation allows the system to adapt to changing conditions when needed while maintaining stability during critical data processing operations.
Solution Approach 2:
The patent implements dynamic control of the adaptation process, adjusting the filter coefficient update frequency based on operating conditions. The system can increase adaptation frequency when I/Q mismatch is expected to change (e.g., frequency tuning events) and reduce it during stable operation or data bursts, optimizing both adaptability and stability.
Data Source
AI summary
Methods and apparatus to compensate for I/Q mismatch in quadrature receivers are disclosed. An example apparatus disclosed herein comprises a correction engine using first filter coefficients to compensate for I/Q mismatch present in a received quadrature signal; an adaptation engine to adapt second filter coefficients based on I/Q mismatch present in the received quadrature signal; and coefficient controller to occasionally adjust the first filter coefficients based on the second filter coefficients.