RF Power Amplifier Supply Control Using Output Distortion Estimation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional RF PA systems face inefficiencies due to fixed biasing, inaccurate power estimation, and impedance changes, leading to suboptimal supply voltage adjustments, which result in reduced power efficiency and increased distortion.
Innovation Solution
A RF PA system that estimates distortion in the output signal by comparing it with reference modulation information and adjusts the supply voltage to maintain a predetermined distortion level, allowing for real-time optimization of power efficiency while minimizing distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the output transistor is biased to remain linear at peak power transmitted, then distortion is reduced and linearity requirements are met, but power efficiency deteriorates during off-peak periods
Solution Approach 1:
The patent applies dynamics by transitioning from fixed biasing to dynamic biasing where the bias point is continuously adjusted based on the instantaneous amplitude of the RF input signal. The bias voltage is modulated in envelope following the input signal, allowing the transistor to operate at optimal efficiency points for each signal level while maintaining linearity when needed.
Solution Approach 2:
The patent changes the bias parameter from a constant DC voltage to a time-varying voltage that follows the envelope of the input signal. This parameter change enables the transistor to operate at different bias points dynamically, improving efficiency during off-peak periods while maintaining acceptable linearity during peak periods.
2Loss of energy
If conventional EER technique is used to vary supply voltage based on amplitude signal, then some efficiency gain is achieved, but significant efficiency improvement is limited due to difficulty in realizing fast accurate voltage converter
Solution Approach 1:
The patent extracts the bias adjustment function from a complex voltage converter and implements it directly at the transistor bias terminals using simple voltage modulation circuits. This eliminates the need for a separate complex EER voltage converter while achieving the same efficiency improvement through direct bias envelope following.
Solution Approach 2:
The patent introduces an envelope detector as an intermediary that extracts the amplitude information from the RF input signal and uses it to modulate the bias voltage. This intermediary simplifies the control mechanism by converting the complex RF signal variation into a simple envelope signal that directly controls the bias point.
3Adaptability or versatility
If linear regulator is used to vary supply voltage at constant current load, then supply voltage can be adjusted, but power efficiency deteriorates due to power consumption in the regulator itself
Solution Approach 1:
The patent applies dynamics by switching from static linear regulation to dynamic switching regulation where the supply voltage is adjusted in discrete steps using PWM control. This dynamic switching approach eliminates the continuous power dissipation inherent in linear regulators while maintaining the ability to adapt supply voltage to signal conditions.
Solution Approach 2:
The patent replaces the linear regulator mechanism with a switching regulator mechanism that uses PWM duty cycle control instead of continuous voltage adjustment. This substitution eliminates the inherent power loss in linear regulators by using high-frequency switching with minimal conduction losses.
4Reliability
If PA output power changes frequently to improve network performance, then communication quality is improved, but power efficiency deteriorates due to suboptimal supply voltage adjustments
Solution Approach 1:
The patent applies feedback by continuously monitoring the RF input signal amplitude and using this information to adjust the bias voltage in real-time. This feedback mechanism ensures that the bias point is always optimized for the current signal level, maintaining high efficiency even when output power changes frequently due to network conditions.
Solution Approach 2:
The patent applies preliminary action by pre-modulating the bias voltage to follow the envelope of the input signal before the signal is amplified. This preliminary bias adjustment prepares the transistor to operate at optimal efficiency points for each signal level, preventing efficiency loss before it occurs during power changes.
Data Source
AI summary
A radio frequency (RF) power amplifier system is provided, in which a distortion of the RF output signal from the power amplifier is estimated by comparing the RF output signal with reference modulation information. The supply voltage to the power amplifier is adjusted so that the estimated distortion of the RF output signal corresponds to a predetermined distortion level. The predetermined distortion level is set to represent an acceptable distortion level at the RF output signal.