Transmit Circuit Bias Adaptation Under Antenna Load Mismatch
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Solution Overview
Problem
Conventional power amplifier bias adjustment methods in mobile communication devices fail to maintain optimal radiated performance under varying load impedances, leading to inefficiencies and increased current consumption, especially when antenna conditions change.
Innovation Solution
A transmit circuit with a bias controller that adjusts the power amplifier's bias based on the measured load impedance, using a combination of an impedance determinator, bias information provider, and DCDC converter to maintain key performance parameters like ACLR and EVM across a range of load impedances, and an envelope tracker to adapt bias information dynamically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional bias control methods are used to adjust power amplifier bias based on output power level, then current consumption is reduced, but radiated performance deteriorates under varying load impedances
Solution Approach 1:
The patent implements a feedback mechanism where the bias controller continuously monitors load impedance conditions and dynamically adjusts the power amplifier bias in response. The bias controller receives information about actual load impedance and modifies bias settings to maintain optimal performance, creating a closed-loop control system that adapts to changing antenna conditions while managing current consumption efficiently
Solution Approach 2:
The patent transitions from static bias control to dynamic bias adjustment by making the bias controller responsive to real-time load impedance variations. The system continuously adapts bias settings based on current operating conditions, enabling the power amplifier to maintain optimal performance across varying antenna states rather than relying on fixed bias levels
2Loss of energy
If bias current is reduced based on detected output power level, then energy efficiency improves, but performance under severe load mismatches deteriorates
Solution Approach 1:
The bias controller uses feedback from load impedance monitoring to determine appropriate bias current levels. Instead of simply reducing bias based on output power, the system receives feedback about actual load conditions and adjusts bias accordingly, maintaining energy efficiency while ensuring adequate performance even under severe load mismatches through informed dynamic adjustment
Solution Approach 2:
The patent changes the control parameter from output power level alone to a combination of output power and load impedance characteristics. By incorporating load impedance information into the bias control decision, the system can optimize energy efficiency while maintaining performance margins for various antenna conditions through parameter-based adaptation
3Power
If antenna tuner transforms antenna impedance, then radiated power improves, but device complexity increases
Solution Approach 1:
The bias controller serves multiple functions: it manages power amplifier bias for normal operation, monitors load impedance conditions, and adapts bias settings in response to antenna tuner operations. By integrating these functions into a single control unit, the patent reduces overall device complexity while maintaining the benefits of antenna impedance transformation for improved radiated power
4Reliability
If bias is adjusted dynamically based on load impedance, then radiated performance is maintained, but control complexity increases
Solution Approach 1:
The patent combines the bias control function with load impedance monitoring and adaptation logic into a single integrated bias controller. By merging these related functions rather than implementing them as separate systems, the patent maintains radiated performance through dynamic bias adjustment while minimizing the increase in control complexity through functional integration
Data Source
AI summary
A transmit circuit includes a power amplifier configured to amplify an RF input signal to obtain an RF output signal, and an antenna tuner configured to transform an antenna impedance to an impedance at an input of the antenna tuner, wherein the input of the antenna tuner is coupled to an output of the power amplifier. The transmit circuit further includes a bias controller configured to control a bias of the power amplifier, wherein the bias controller is configured to provide a bias control signal to adjust the bias of the power amplifier based on a determination of a measure of a load impedance provided to the power amplifier by the antenna tuner.