Baseband IQ Mismatch Compensation via Lookup Table
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Solution Overview
Problem
In wireless communication systems, IQ mismatch between in-phase and quadrature-phase signals due to phase and gain imbalances leads to poor reception performance, which existing calibration methods are inefficient and time-consuming to correct.
Innovation Solution
A baseband system and method that includes an estimation and compensation circuit to estimate and compensate for frequency-independent non-ideal effects in IQ signals, followed by channel estimation and equalization, and tracking and compensation to address residual quantities, thereby generating an output IQ signal pair without the need for extensive offline calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a calibration procedure is performed to determine the deviation of phase difference from 90°, then the IQ mismatch problem is solved, but it takes a lot of time
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing compensation values in a lookup table during manufacturing or system initialization. The baseband processing unit directly queries this pre-prepared table to obtain compensation values without performing real-time calibration, thereby eliminating time-consuming calibration procedures while maintaining accurate phase difference correction.
Solution Approach 2:
The patent changes the parameter representation by converting continuous phase difference calibration into discrete lookup table entries. By pre-computing compensation values for various phase deviation scenarios and storing them in the lookup table, the system transforms a time-intensive continuous calibration process into a fast discrete parameter retrieval operation.
2Measurement precision
If RF circuit calibration is performed to correct phase difference, then phase accuracy is improved, but gain/phase imbalance causes incorrect deviation calculation
Solution Approach 1:
The patent extracts the calibration function from the RF circuit domain and relocates it to the baseband processing domain. By separating the phase difference measurement and compensation functions from the RF calibration process, the system eliminates the interfering effect of RF gain/phase imbalance on calibration accuracy, allowing independent and accurate phase error correction.
Solution Approach 2:
The patent introduces a lookup table as an intermediary between the received signal and the compensation action. This lookup table stores pre-computed compensation values that mediate the correction process, allowing the baseband processing unit to apply accurate phase compensation without being affected by RF circuit imperfections.
3Measurement precision
If extensive calibration procedures are performed, then IQ mismatch is corrected, but system complexity and processing time increase
Solution Approach 1:
The patent applies preliminary action by pre-computing and storing all necessary compensation values in a lookup table during system initialization or manufacturing. This eliminates the need for complex real-time calibration procedures, reducing both system complexity and processing time while maintaining signal accuracy through direct table lookup and application of pre-determined compensation values.
Data Source
AI summary
A baseband system includes: an estimation and compensation circuit estimating frequency-independent non-ideal effects based on an original IQ signal pair, and compensating the original IQ signal pair based on a result of the estimation to obtain a compensated IQ signal pair; a channel estimation and equalization circuit performing channel estimation and equalization based on the compensated IQ signal pair to obtain an equalized IQ signal pair; and a tracking and compensation circuit obtaining a result of tracking of residual quantities of the aforesaid non-ideal effects based on the equalized IQ signal pair, and compensating the equalized IQ signal pair based on the result of the tracking to obtain an output IQ signal pair.