Wireless Transceiver Digital I/Q Calibration for Image Rejection
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Solution Overview
Problem
Wireless transceivers face challenges in rejecting image signals due to mismatches in amplitude and phase between in-phase (I) and quadrature-phase (Q) signals, which can lead to distortion and failure to meet signal requirements such as spectral masks.
Innovation Solution
A wireless transceiver is designed to include a method for digital I/Q calibration, where a simulated image frequency signal is used in a loopback to determine and apply adjustments to the receiver's I/Q signals, ensuring they are at the same amplitude and 90 degrees out of phase, thereby improving image rejection during operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If digital I/Q calibration adjustment is applied to improve image rejection, then image signal rejection is improved, but device complexity increases
Solution Approach 1:
The patent applies preliminary action by performing I/Q calibration adjustments before normal receiver operation. A calibration signal is injected and processed through the receiver chain to determine optimal I/Q mismatch compensation values, which are then stored and applied during subsequent operations. This preliminary calibration eliminates the need for complex real-time adjustment mechanisms during signal reception.
Solution Approach 2:
The system performs self-calibration by automatically determining I/Q mismatch parameters using an internal calibration signal path. The receiver uses its own hardware components (mixers, amplifiers, ADCs) to generate and process a calibration signal, eliminating the need for external calibration equipment and reducing overall system complexity.
2Measurement precision
If loopback calibration method is used to determine I/Q calibration adjustment, then calibration accuracy is improved, but ease of operation deteriorates
Solution Approach 1:
The patent introduces an intermediary calibration signal path that loops back from the transmitter through the receiver chain to a calibration input. This intermediary path allows the system to measure I/Q mismatch under controlled conditions without requiring external test equipment or complex manual procedures. The calibration signal acts as a mediator that enables automatic parameter extraction.
Solution Approach 2:
The system implements feedback by routing the transmitted calibration signal back through the receiver and using the received signal to automatically determine I/Q calibration parameters. The digital signal processor analyzes the loopback signal and adjusts calibration values based on measured mismatches, creating a closed-loop calibration system that improves accuracy while maintaining ease of operation through automation.
Data Source
AI summary
Various embodiments are disclosed relating to a wireless transceiver. In an example embodiment, a wireless transceiver may include a transmitter adapted to output a signal at an image frequency (e.g., a simulated image) for a channel during a first mode (e.g., calibration mode) of operation. The wireless transceiver also includes a receiver adapted to receive, via loopback from the transmitter, the (e.g., simulated) image frequency signal and to determine digitally a receiver in-phase/quadrature-phase (I/Q) signal calibration adjustment based on the (simulated) image frequency signal to improve a match in amplitude and a predetermined phase shift between I and Q signals of the receiver during the first (e.g., calibration) mode of operation. The I/Q calibration adjustment may be applied to received signals during a second mode (e.g., operation mode) of operation to improve image rejection.