Blind Transmitter IQ Imbalance Compensation Using Inversion Matrix
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Solution Overview
Problem
IQ imbalance between in-phase and quadrature branches in communication systems leads to signal distortion, limiting the achievable signal-to-noise ratio and data rates, especially in low-cost and power-sensitive applications like direct-conversion receivers, and existing compensation methods require significant memory and may not adapt well to changes in transmitter IQ imbalance.
Innovation Solution
A method for blind IQ imbalance compensation that estimates and corrects transmitter IQ imbalance by collecting statistics over multiple data bit transmissions, calculating an inversion matrix based on these statistics, and applying it to sub-carriers and their images to remove the imbalance without interrupting the communication link or requiring extensive memory storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional IQ imbalance compensation methods are used, then signal quality can be improved, but memory requirements and system complexity increase significantly
Solution Approach 1:
The patent extracts only the essential statistical properties (correlation between subcarrier and image subcarrier) needed for IQ imbalance compensation, rather than storing complete channel state information. By collecting statistics over multiple transmissions and extracting the critical correlation parameter, the system achieves compensation with minimal memory storage requirements.
Solution Approach 2:
The patent changes the approach from storing complete channel matrices to storing only the essential statistical correlation parameter between subcarriers and image subcarriers. This parameter transformation reduces the memory footprint from O(N²) to O(1) while maintaining compensation effectiveness.
2Reliability
If existing compensation methods are applied, then IQ imbalance can be corrected, but the system cannot adapt well to changes in transmitter IQ parameters
Solution Approach 1:
The patent implements a feedback mechanism where the receiver continuously collects statistics from incoming signals, updates the correlation parameter estimates, and recalculates compensation coefficients. This ongoing statistical collection and update process enables the system to adapt to changes in transmitter IQ parameters without requiring reconfiguration or training sequences.
Solution Approach 2:
The patent performs preliminary statistical analysis by collecting data over multiple transmissions before applying compensation. By pre-collecting and analyzing the statistical properties of the received signals, the system prepares accurate compensation coefficients that account for transmitter-specific IQ imbalances before actual data transmission begins.
3Measurement precision
If more memory is allocated for compensation, then compensation accuracy improves, but cost and power consumption increase
Solution Approach 1:
The patent uses lightweight statistical moments (mean and correlation) that can be computed and discarded after use, rather than storing large channel matrices. These minimal statistical descriptors provide sufficient compensation accuracy while occupying negligible memory space, effectively replacing heavy memory-dependent solutions with computationally light alternatives.
4Measurement precision
If training sequences are used for compensation, then accuracy improves, but communication efficiency decreases due to link interruptions
Solution Approach 1:
The patent enables the system to perform self-calibration by extracting IQ imbalance characteristics directly from the data transmissions themselves. The receiver uses the received data symbols to compute statistical correlations and derive compensation parameters without requiring external training sequences or manual calibration, thus maintaining continuous communication while achieving accurate compensation.
Data Source
AI summary
Systems and methods of correcting for a transmitter IQ imbalance are disclosed. Various embodiments collect statistics related to a received packet on a transceiver. These statistics include one or more transmitter imbalance parameters. In some embodiments, an estimated inversion matrix is calculated based on the imbalance parameter and a correction for the IQ imbalance is made by applying the inversion matrix to a sub-carrier and the sub carrier's image.