Tunable Auxiliary Receiver Feedback for Multi-Band IQ Imbalance
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Solution Overview
Problem
Existing mobile transceivers face performance degradation due to initial IQ imbalances, which increase Bit Error Rate (BER) and are challenging to compensate for over process and temperature variations, especially in multi-band systems.
Innovation Solution
A communications device with a frequency tunable auxiliary receiver and controller that applies predistortion to wireless transmitters to reduce initial IQ imbalances, utilizing a switching block and digital signal processing to generate and apply predistortion signals, and includes a phase locked loop and power amplifier to correct IQ signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If mixers are designed to be precisely 90 degrees in phase delay to reduce IQ imbalance, then IQ imbalance is reduced, but manufacturing precision becomes difficult to maintain over process and temperature variations
Solution Approach 1:
The patent implements a feedback mechanism where the auxiliary receiver monitors the IQ signals and the controller adjusts the predistortion parameters based on the observed IQ imbalance. This closed-loop feedback allows the system to automatically compensate for phase variations caused by process and temperature changes, maintaining reliable performance without requiring extremely precise initial mixer design.
Solution Approach 2:
The patent applies predistortion to the IQ signals before they reach the mixers. By pre-compensating for the expected IQ imbalance through digital signal processing, the system reduces the criticality of precise physical mixer design. The predistortion parameters can be adjusted based on calibration data, making the system less sensitive to manufacturing variations.
2Device complexity
If a single auxiliary receiver is used to provide feedback for multiple transmitters, then device complexity and cost are reduced, but the ability to simultaneously correct multiple frequency signals becomes challenging
Solution Approach 1:
The patent designs the auxiliary receiver and controller as universal components that can handle multiple frequency bands and transmitter configurations. The frequency tunable auxiliary receiver can be programmed to operate at different frequencies, and the controller can apply different predistortion parameters based on the active transmitter. This multi-functional design allows a single auxiliary receiver to serve multiple transmitters across different frequency bands, reducing device complexity while maintaining adaptability.
3Reliability
If predistortion is applied to reduce IQ imbalance, then signal quality is improved, but additional signal processing complexity is introduced
Solution Approach 1:
The patent replaces physical hardware adjustments (such as precise mechanical mixer design and manual calibration) with digital signal processing. The predistortion is implemented through digital algorithms in the controller, which can be programmed and adjusted without changing physical components. This substitution reduces the complexity of physical design and assembly while maintaining or improving signal quality through flexible digital correction.
Data Source
AI summary
A communications device includes a plurality of wireless transmitters operable at different respective frequencies and each configured to generate respective IQ signals having an initial IQ imbalance. The communications device also includes a frequency tunable auxiliary receiver, and a controller. The controller is configured to selectively couple a given wireless transmitter to the frequency tunable auxiliary receiver and tune the frequency tunable auxiliary receiver to a frequency of the given wireless transceiver, and apply predistortion to the given wireless transmitter based upon the initial IQ imbalance to reduce the initial IQ imbalance.