Calibrating Quadrature Imbalance via Loopback Phase Shifts
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Solution Overview
Problem
Direct conversion transceivers face quadrature imbalance issues due to gain and phase mismatches between in-phase (I) and quadrature (Q) channels, which impair signal-to-noise ratio and increase bit errors, especially in high-speed wireless communications and MIMO systems.
Innovation Solution
A method and apparatus for calibrating quadrature imbalance in direct conversion transceivers involve injecting a single-frequency signal and generating phase-shifted signals using a phase-shifting module, allowing for the calculation of correction parameters to adjust elements and correct quadrature imbalance in both transmitter and receiver paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If direct conversion transceivers are used for high-speed wireless communications, then data transmission speed is improved, but quadrature imbalance increases causing signal-to-noise ratio degradation and bit errors
Solution Approach 1:
The patent applies preliminary action by performing quadrature imbalance calibration before normal data transmission. The system injects calibration signals, measures the actual I and Q channel characteristics, calculates correction parameters, and applies compensation factors in advance. This preliminary calibration ensures that when high-speed data transmission occurs, the quadrature imbalance has already been corrected, maintaining both high speed and signal quality without interference between data and calibration operations.
2Adaptability or versatility
If separate I and Q channel paths are used in direct conversion transceivers, then quadrature signal generation capability is improved, but gain and phase mismatches between channels increase causing quadrature imbalance
Solution Approach 1:
The patent implements feedback by measuring the actual output signals from the I and Q channels during calibration, comparing them against expected values, calculating the discrepancy (quadrature imbalance), and using this feedback to determine correction parameters. The system continuously monitors the phase and gain differences and applies compensating factors to adjust the I and Q channel characteristics, creating a closed-loop system that automatically corrects manufacturing mismatches while preserving the benefits of separate channel paths.
Data Source
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AI summary
Apparatuses, systems, and methods for correction of mismatches are provided, the apparatus including a signal generator to generate a signal for calibration for a radio frequency (RF) portion of a transmitter or an RF portion of a receiver of a direct-conversion architecture to calibrate for mismatches of in-phase and quadrature (I/Q) signals, at least one of the RF portions coupled by a loopback path, and the loopback path to couple first and second signals based upon the signal generated for calibration to the RF portion of the receiver, the loopback path including a phase-shifting module to shift the signal generated for calibration as propagated through a portion of the transmitter to generate the second signal with a different phase from the first signal, wherein the apparatus is configured to digitally correct mismatches of I/Q signals in the receiver and the transmitter based upon the first and second signals.