Predistortion Calibration Path Isolation for PA Loopback Accuracy
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Solution Overview
Problem
Existing predistortion calibration systems in wireless communications devices face challenges due to parasitic coupling paths, which lead to inaccuracies in loopback operations and reduced fidelity, affecting the ability to accurately replicate transmitter path non-ideal effects and cancel them effectively.
Innovation Solution
The implementation of a separate power amplifier predistortion calibration path with its own transconductance stage, isolated from the main receiver path, uses a secondary transconductance stage exclusively for loopback operations to mitigate parasitic coupling, improving fidelity and accuracy of predistortion by suppressing noise and stray coupling paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a shared transconductance stage is used for both receiver and predistortion calibration paths, then device complexity is reduced, but parasitic coupling paths are introduced that reduce measurement precision
Solution Approach 1:
The patent divides the transconductance functionality into separate stages: a first transconductance stage for the receiver path and a second transconductance stage for the predistortion calibration path. This segmentation eliminates parasitic coupling between the paths while maintaining functional independence, resolving the contradiction between device complexity and measurement precision.
Solution Approach 2:
The patent extracts the predistortion calibration function from the shared receiver path by implementing a dedicated second transconductance stage. This extraction removes the parasitic coupling paths that would otherwise interfere with loopback operations, achieving high measurement precision without excessive complexity increase.
2Reliability
If the predistortion calibration path is isolated from the receiver path, then parasitic coupling is reduced improving fidelity, but device complexity and component count increase
Solution Approach 1:
The patent merges the first and second transconductance stages into a single integrated circuit structure. This merging approach allows the predistortion calibration path to be isolated from the receiver path for improved fidelity, while avoiding the complexity of completely separate implementations. The stages share common circuit elements where appropriate, reducing overall device complexity.
3Measurement precision
If a secondary transconductance stage is added for predistortion calibration, then loopback operation accuracy is improved, but manufacturing complexity increases
Solution Approach 1:
The patent segments the transconductance functionality into distinct stages that can be independently optimized during manufacturing. The first transconductance stage serves the receiver path while the second stage serves the predistortion calibration path, allowing each to be manufactured with appropriate precision requirements without compromising the other.
Solution Approach 2:
The patent combines both transconductance stages within a single integrated circuit implementation, which simplifies manufacturing compared to discrete implementations. The merged structure allows for standardized fabrication processes while maintaining the functional separation needed for high loopback operation accuracy.
Data Source
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AI summary
In one embodiment, a method comprising during a first calibration instance, converting at a first transconductance stage a first output voltage from a power amplifier of a transceiver to a first set of current signals; and during a second calibration instance not overlapping the first calibration instance, converting at a second transconductance stage a second output voltage from the power amplifier to a second set of current signals.