Electrothermal PA Bias Feedback for Flat Burst Gain
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Solution Overview
Problem
Existing power amplifier (PA) systems face challenges in maintaining constant gain during long and short burst operations due to temperature fluctuations, which affect dynamic error vector magnitude (DEVM), especially in wireless local area network (WLAN) PAs, and current solutions are either complex, costly, or ineffective across varying burst lengths and temperatures.
Innovation Solution
The implementation of electrothermal feedback circuitry that automatically adjusts the bias voltage based on thermal feedback to maintain a constant PA gain, using a configuration with transistors Q1 and Q2 to convert temperature profiles into electrical currents and adjust bias voltages, allowing for adjustable resistance control to compensate for gain deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If amplitude tracking is implemented to correct gain deviation, then gain correction is achieved, but system power consumption increases and system complexity increases
Solution Approach 1:
The patent implements an electrothermal feedback mechanism where the PA cell's own temperature rise during operation is fed back through a thermally coupled transistor to automatically adjust the bias voltage. This closed-loop feedback system corrects gain deviation without requiring external amplitude tracking circuits, thereby reducing system complexity while maintaining gain correction capability.
Solution Approach 2:
The PA cell serves itself by using its own temperature characteristics to generate the correction signal. The thermally coupled transistor Q2 converts the temperature profile into an electrical current that automatically adjusts the bias voltage, eliminating the need for external control circuits and reducing overall system complexity.
2Manufacturing precision
If speed-up circuit with RC components is used to control burst gain profile, then gain profile control is improved, but device complexity increases and component tolerance issues arise
Solution Approach 1:
The patent extracts and eliminates the complex RC speed-up circuit components by replacing them with a simplified electrothermal feedback mechanism using thermally coupled transistors. This removes multiple resistors and capacitors from the circuit, reducing component count and eliminating tolerance accumulation issues while maintaining gain profile control capability.
Solution Approach 2:
The patent replaces the electrical RC circuit mechanism with a thermal field mechanism. Instead of using resistors and capacitors to shape the gain profile, the system uses thermal coupling between transistors to transfer temperature information and achieve the same control objective with fewer components.
3Adaptability or versatility
If PA operates during long and short bursts, then versatility is improved, but gain stability deteriorates due to temperature fluctuations
Solution Approach 1:
The patent dynamically adjusts the bias voltage parameter based on real-time temperature changes during different burst durations. The electrothermal feedback mechanism continuously monitors temperature and modifies the bias point to compensate for thermal effects, maintaining gain stability across varying burst lengths and operating conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively maintains a flat gain profile over time and improves DEVM by directly sensing temperature deviations, reducing component tolerance issues and avoiding the need for large capacitors, while ensuring compliance with strict turn-on time specifications and minimizing RF coupling.
Implementation Method 1
electrothermal feedback circuitry configured to receive thermal feedback generated by the PA and maintain a substantially constant PA gain by automatically changing a bias voltage level at the bias input based upon the thermal feedback
Data Source
AI summary
A power amplifier (PA) system with PA gain correction is disclosed. The PA system includes a PA having a bias voltage input; and electrothermal feedback circuitry coupled to the bias voltage input. The electrothermal feedback circuitry is configured to receive thermal feedback generated by the PA and maintain a substantially constant PA gain by automatically changing a bias voltage level at the bias voltage input based upon the thermal feedback.