Optical Transmitter IQ Imbalance Compensation Using Transform Matrices
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Solution Overview
Problem
Existing methods for estimating and compensating IQ imbalance in optical transmitters are prone to unstable phase offset estimation and poor accuracy, especially at larger angles, leading to distorted constellation diagrams and increased bit error rates.
Innovation Solution
An estimation and compensation apparatus using a transform matrix based on received and transmitted signals to accurately estimate phase offset shifts, ensuring precise recovery of the constellation diagram.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If Gram-Schmidt orthogonalization (GSOP) is used for IQ imbalance estimation, then the method is simple to implement, but the phase offset estimation becomes unstable and accuracy deteriorates at larger angles
Solution Approach 1:
The patent changes the fundamental parameter of the estimation approach from GSOP-based to transform matrix-based. The transform matrix method uses a different mathematical model that represents the relationship between transmitted and received signals, allowing accurate estimation of amplitude imbalance ratio and phase offset across all angles without the instability issues of GSOP
Solution Approach 2:
The patent replaces the GSOP mechanical process with a transform matrix mathematical model. Instead of using Gram-Schmidt orthogonalization operations, the system uses matrix transformations to directly compute the IQ imbalance parameters, achieving both simplicity and high accuracy
2Reliability
If GSOP-based compensation is applied, then the constellation diagram can be recovered, but the symmetry axis becomes offset from the rectangular axis causing decision errors
Solution Approach 1:
The patent introduces feedback mechanisms where the estimated transform matrix parameters are used to compensate the received signals, and the compensation results are used to verify and refine the estimation. This feedback loop ensures that the constellation diagram is not only recovered but also properly aligned with the rectangular axis, eliminating decision errors
Solution Approach 2:
The patent performs preliminary estimation of the transform matrix parameters before compensation is applied. By accurately determining the amplitude imbalance ratio and phase offset in advance, the system can apply the correct compensation to restore the constellation diagram with proper symmetry axis alignment
3Ease of operation
If existing estimation methods are used, then the process is straightforward, but bit error rates increase due to distorted constellation diagrams
Solution Approach 1:
The patent changes the estimation parameters from GSOP-based to transform matrix-based parameters (amplitude imbalance ratio and phase offset). This parameter transformation enables accurate characterization of the IQ imbalance, leading to proper compensation and significant reduction in bit error rates while maintaining operational simplicity
Data Source
AI summary
An estimation apparatus for IQ imbalance of an optical transmitter, a compensation apparatus for IQ imbalance of an optical transmitter and electronic equipment; wherein, estimation and compensation of IQ imbalance of an optical transmitter are performed by directly using an estimation model based on a transform matrix of received signals and transmitted signals, therefore, a phase offset shift may be estimated accurately, and precision of estimation of drifts of various angles is ensured, furthermore, accurate recovery of the constellation diagram of received signals is achieved.