RF Power Amplifier Supply Control Using Distortion Feedback
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Solution Overview
Problem
Conventional RF power amplifier systems face inefficiencies due to fixed supply voltage, inaccurate power estimation, changing peak-to-average ratio, and impedance variations, leading to suboptimal performance and increased spectral occupancy.
Innovation Solution
A power amplifier controller adjusts the supply voltage based on real-time distortion measurements, using an amplitude error signal and deviation signal to maintain acceptable distortion levels, allowing for efficient operation closer to saturation points while minimizing voltage headroom.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the supply voltage is reduced to increase efficiency, then power consumption decreases, but distortion increases and spectral occupancy widens
Solution Approach 1:
The patent implements a feedback mechanism where the actual output power is measured and compared with the expected output power to generate an error signal. This error signal is used to adjust the supply voltage dynamically, ensuring that distortion remains within acceptable limits while maximizing efficiency. The feedback loop continuously monitors and corrects the relationship between supply voltage and output power.
Solution Approach 2:
The patent transitions from fixed biasing to dynamic supply voltage adjustment. The supply voltage is no longer static but varies in real-time based on the measured output power and the generated error signal. This dynamic approach allows the system to operate at optimal efficiency points while adapting to changing conditions to maintain acceptable distortion levels.
2Object-generated harmful factors
If fixed biasing is used to maintain linearity at peak power, then distortion is controlled, but efficiency drops during off-peak periods
Solution Approach 1:
The patent replaces fixed biasing with dynamic supply voltage adjustment that adapts to the actual output power level. During off-peak periods, the supply voltage is reduced to match the lower power demands, eliminating the power waste associated with fixed biasing. The system maintains acceptable distortion by continuously adjusting the voltage based on real-time measurements.
Solution Approach 2:
The patent changes the supply voltage parameter dynamically rather than maintaining a fixed value. The voltage is adjusted according to the measured output power and the error signal, allowing the system to optimize efficiency at different power levels while maintaining linearity when needed.
3Loss of energy
If supply voltage is lowered to improve efficiency, then power consumption decreases, but voltage headroom is insufficient leading to increased distortion
Solution Approach 1:
The feedback mechanism measures actual output power and generates an error signal that adjusts the supply voltage to maintain adequate headroom. The system learns the relationship between voltage and power output, ensuring that voltage is never reduced below the level needed to maintain reliable operation and acceptable distortion.
Solution Approach 2:
The system performs preliminary measurements to establish the relationship between supply voltage and output power. This preliminary characterization allows the control algorithm to predict the minimum voltage needed for reliable operation, preventing insufficient headroom before it occurs.
4Device complexity
If conventional power estimation is used, then simplicity is maintained, but accuracy decreases leading to suboptimal efficiency
Solution Approach 1:
The patent replaces conventional open-loop power estimation with closed-loop feedback measurement. The actual output power is measured and fed back to generate an error signal, providing accurate real-time information about the relationship between supply voltage and output power. This feedback mechanism significantly improves estimation accuracy while adding manageable complexity.
Data Source
AI summary
A power amplifier controller for adjusting a supply voltage to a power amplifier. The power amplifier controller adjusts the supply voltage so that distortion in an RF output signal corresponds to a predetermined limit. An amplitude error signal is generated by the power amplifier controller which represents a difference between an RF output signal and an attenuated RF output signal. The AC components of the amplitude error signal are processed to generate a deviation signal that represents the distortion in the RF output signal. The supply voltage to the power amplifier is increased when the deviation signal exceeds a distortion level control signal, and decreased when the deviation signal drops below the distortion level control signal.