RF Power Amplifier Supply Control Under Impedance Mismatch
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional RF PA controllers fail to adaptively adjust the supply voltage in response to changes in RF output signal power and impedance, leading to inefficiencies and distortion in RF power amplifiers used in portable devices.
Innovation Solution
An RF PA system that dynamically adjusts the supply voltage based on measured or estimated RF output signal power and impedance mismatch, using a PA VCC controller to generate a supply voltage control signal, and optionally includes a phase correction loop or impedance adjustment to optimize efficiency and reduce distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the supply voltage is lowered to improve power efficiency, then the PA operates closer to saturation and efficiency increases, but the voltage headroom becomes insufficient causing unacceptable distortion
Solution Approach 1:
The patent applies dynamics by making the supply voltage adjustable rather than fixed. The PA controller dynamically changes the supply voltage to the final amplification stage based on operating conditions, allowing the system to optimize between efficiency and linearity requirements at different power levels
Solution Approach 2:
The patent changes the supply voltage parameter adaptively. By monitoring the operating state and adjusting the supply voltage to the final stage, the system can operate at lower voltages (improving efficiency) when linearity requirements are less stringent, while maintaining higher voltages when low distortion is critical
2Manufacturing precision
If the bias is kept fixed to maintain linearity at peak power, then acceptable distortion is achieved, but power efficiency falls to below 30% during off-peak periods
Solution Approach 1:
The patent makes the bias dynamic by allowing it to change based on the operating state. The PA controller adjusts the bias to the final stage according to the instantaneous power level and modulation requirements, enabling high efficiency during off-peak periods while maintaining acceptable linearity when needed
Solution Approach 2:
The patent implements periodic adjustment of bias and supply voltage parameters that track the modulation envelope. This allows the system to optimize efficiency during low-power portions of the modulation cycle while maintaining linearity during peak power transmission
3Device complexity
If a fixed supply voltage is used to simplify the power supply design, then device complexity is reduced, but the PA cannot adapt to changing output power requirements and efficiency deteriorates
Solution Approach 1:
The patent implements feedback by having the PA controller monitor the operating state (including output power level and modulation characteristics) and use this information to adjust the supply voltage to the final stage. This closed-loop control enables adaptive efficiency optimization without requiring a completely complex power supply architecture
Solution Approach 2:
The PA controller is given multi-functionality, serving both as the main control unit and as the supply voltage regulator for the final stage. This consolidates control functions and reduces overall system complexity while achieving adaptive efficiency
Data Source
AI summary
A radio frequency (RF) power amplifier system adjusts the supply voltage provided to a power amplifier (PA) adaptively, responsive to the measured or estimated power of the RF output signal of the PA. The RF PA system includes a power amplifier (PA) which receives and amplifies an RF input signal to generate an RF output signal at a level suitable for transmission to an antenna. A PA supply voltage controller generates a supply voltage control signal, which is used to control the supply voltage to the final stage of the PA. The supply voltage control signal is generated responsive to the measured or estimated power of the PA RF output signal, and also may be responsive to a parameter indicative of impedance mismatch experienced at the PA output. By controlling this supply voltage to the RF PA, the efficiency of the PA is improved.