Transmitter Gain Control Using EVM Feedback for Distortion Limits
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Solution Overview
Problem
Existing power control schemes in electronic data communication, such as open loop and closed loop power control, often result in unnecessarily low transmitted power levels due to distortion, and pre-distortion schemes have limitations in addressing these issues effectively.
Innovation Solution
A system that measures the linearity of a transmitter using digital indications like error vector magnitude and spectral masks, and adjusts the gain setting based on these measurements, along with other factors like power level, voltage, and temperature, to optimize the transmitted signal power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transmitted power is increased to improve signal quality, then signal quality is improved, but distortion increases causing data loss and high bit error rates
Solution Approach 1:
The patent implements a feedback mechanism where the receiver measures the error vector magnitude (EVM) of the received signal and feeds this information back to the transmitter. The transmitter then adjusts its gain setting based on the measured EVM to optimize power output while maintaining signal quality and avoiding distortion. This closed-loop feedback system resolves the contradiction by dynamically balancing power level and distortion based on actual transmission conditions.
Solution Approach 2:
The system dynamically changes the gain parameter of the transmitter based on measured EVM values. By adjusting the gain setting in response to measured distortion levels, the system optimizes the transmitted power to achieve the best signal quality without exceeding distortion thresholds, thus resolving the trade-off between signal quality and distortion.
2Object-generated harmful factors
If known power level error is subtracted from target power level to avoid exceeding maximum power levels, then maximum power level compliance is maintained, but transmitted power levels become unnecessarily low
Solution Approach 1:
Instead of using a fixed conservative power level, the system uses feedback from EVM measurements to dynamically adjust the transmitted power. This allows the system to transmit at higher power levels when conditions permit, while still maintaining compliance with maximum power limits and avoiding distortion, thus resolving the contradiction between power compliance and transmitted power level.
Solution Approach 2:
The system performs self-adjustment by measuring its own transmission quality through EVM and automatically modifying its gain setting accordingly. This self-service mechanism eliminates the need for conservative fixed power settings, allowing the system to optimize its own power output based on real-time performance feedback.
3Device complexity
If open loop power control is used to simplify the control scheme, then device complexity is reduced, but large errors occur due to factors such as temperature and voltage standing wave ratio
Solution Approach 1:
The patent implements a feedback-based closed loop control system where the receiver measures EVM and feeds this information back to the transmitter for gain adjustment. This feedback mechanism compensates for environmental factors like temperature and VSWR variations, significantly improving power level accuracy compared to open loop control, while maintaining reasonable system complexity.
4Object-generated harmful factors
If pre-distortion schemes are used to address distortion, then distortion is compensated, but device complexity increases due to additional modules
Solution Approach 1:
The patent uses a feedback-based gain control mechanism that measures EVM and adjusts the transmitter gain accordingly. This approach provides distortion compensation through a relatively simple feedback loop compared to complex pre-distortion schemes, achieving effective distortion management with minimal additional system complexity.
Data Source
AI summary
Apparatus having corresponding methods and non-transitory computer-readable media comprise: a transmitter configured to transmit a signal according to a gain setting, wherein the signal represents a first digital signal; a receiver configured to receive the signal transmitted by the transmitter, and produce a second digital signal based on the signal received by the receiver; a measurement module configured to produce a digital indication of a linearity of the transmitter based on the second digital signal; and a gain setting module configured to control the gain setting in accordance with the digital indication of the linearity of the transmitter.