I/Q Impairment Correction via 2x2 Digital Filter Matrix
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Solution Overview
Problem
Current systems face challenges in accurately measuring and correcting for In-phase/Quadrature (I/Q) impairments in transmitter and receiver devices, which lead to unwanted energy and distortion in signals, affecting communication quality.
Innovation Solution
A method involving a 2×2 matrix of digital filters is used to compensate for I/Q impairments by computing frequency responses based on measurements of gain imbalance and phase skew, allowing for partial compensation of I/Q impairments in both transmitters and receivers, either through pre-compensation or post-compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional measurement methods are used to estimate I/Q impairments, then the measurement process is simple, but the measurement precision is degraded due to receiver I/Q impairments and signal path distortion corrupting the estimates
Solution Approach 1:
The patent segments the measurement process into distinct phases: transmitting known test signals, receiving distorted signals, and computationally separating the transmitter I/Q impairments from receiver I/Q impairments and signal path effects. This segmentation allows for more precise measurement by isolating the specific impairments being measured, rather than obtaining a corrupted composite measurement as in traditional methods.
Solution Approach 2:
The patent employs feedback mechanisms where the receiver uses its own known I/Q impairment characteristics to correct the measured signals, and the system iteratively refines the estimation of transmitter I/Q impairments. This feedback loop enables the system to compensate for receiver impairments and signal path distortion, significantly improving measurement precision beyond what simple open-loop methods can achieve.
2Object-generated harmful factors
If I/Q impairments are not corrected, then the device complexity is low, but unwanted energy and distortion increase in the transmitted and received signals
Solution Approach 1:
The patent applies preliminary action by measuring and characterizing the I/Q impairments of the transmitter before actual signal transmission. The system uses known test signals to pre-determine the impairment parameters, which are then stored and used to correct subsequent transmissions. This preliminary measurement and characterization approach allows the system to eliminate unwanted energy and distortion without adding complexity to the real-time transmission path.
Solution Approach 2:
The patent changes the parameters of the transmitted signal by applying correction factors derived from the measured I/Q impairments. The system adjusts the in-phase and quadrature signal parameters to compensate for gain imbalances and phase skews, thereby reducing unwanted image signals and distortion. This parameter adjustment approach effectively eliminates harmful factors while maintaining system simplicity through software-based correction.
Data Source
AI summary
Communication devices and associated methods for reducing I/Q impairments in signals used by the communication devices are described. A transmitter device may perform filtering (or matrix multiplication) on digital I and Q signals to pre-correct them before converting them into analog I and Q signals. The pre-correction may pre-compensate for I/Q impairments which have not been introduced yet, but which will subsequently be introduced during digital-to-analog conversion, I/Q modulation, or other processing that occurs to produce a transmission signal from the original digital I and Q signals. A receiver device may receive a transmission signal, produce digital I and Q signals from the received signal, and perform filtering on the digital I and Q signals to correct I/Q impairments at a plurality of frequency offsets.