Variable Supply Voltage Control for RF Power Amplifier Efficiency
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Solution Overview
Problem
Mobile power amplifiers face reduced efficiency due to operating under power back-off conditions to accommodate large peak-to-average ratios in radio frequency signals, leading to decreased battery life in mobile devices.
Innovation Solution
Incorporating a DC-DC converter to control a variable supply voltage for power amplifier circuitry, such as Doherty or Chireix configurations, allowing the power amplifier to operate close to saturation across various output power levels, thereby enhancing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power amplifier is configured to amplify peak signals without distortion, then the peak level can be accommodated, but the average output power must be backed-off, resulting in reduced efficiency
Solution Approach 1:
The patent employs dynamic supply voltage control where the supply voltage to the power amplifier is adjusted in real-time based on the instantaneous signal amplitude. During peak signal periods, the supply voltage is increased to allow operation near saturation without distortion. During average signal periods, the supply voltage is reduced to maintain high efficiency. This dynamic adaptation resolves the contradiction by making the operating point flexible rather than fixed.
Solution Approach 2:
The invention changes the supply voltage parameter dynamically to optimize both signal fidelity and efficiency. By varying the supply voltage according to signal conditions, the power amplifier can operate at different points on its efficiency curve - near saturation for peak signals to maintain fidelity, and at lower supply voltage for average signals to improve efficiency. This parameter modulation resolves the trade-off between these two competing requirements.
2Use of energy by moving object
If the power amplifier operates close to saturation for maximum output power, then efficiency is maximized, but the dynamic range is limited and cannot accommodate large peak-to-average ratios
Solution Approach 1:
The patent makes the power amplifier dynamically adaptable by implementing supply voltage control that responds to signal conditions. When the input signal approaches peak levels, the supply voltage is increased to expand the dynamic range and prevent clipping. When the signal is at average levels, the supply voltage is reduced to maintain efficiency. This dynamic range expansion through voltage modulation allows the amplifier to accommodate large peak-to-average ratios while maintaining high efficiency during average operation.
Solution Approach 2:
The system performs preliminary action by anticipating signal peaks and adjusting the supply voltage accordingly. The supply voltage control mechanism proactively increases voltage before peak signals occur, ensuring the power amplifier has sufficient headroom to handle peaks without distortion. This preliminary adjustment of the operating point allows the amplifier to maintain both high efficiency during average operation and adequate dynamic range when needed.
3Adaptability or versatility
If the output power level is reduced to accommodate average signal levels, then the peak-to-average ratio can be handled, but the efficiency drops significantly
Solution Approach 1:
The patent resolves this contradiction by making the supply voltage dynamic rather than static. Instead of reducing the output power level permanently to handle peak-to-average ratios, the system maintains high supply voltage during peak periods to preserve efficiency, and only reduces voltage when signals are at average levels. This dynamic voltage control allows the amplifier to handle large peak-to-average ratios without sacrificing efficiency during peak operation, as the supply voltage is adjusted to match the instantaneous signal requirements.
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
The solution maintains high efficiency under power back-off conditions, extending the dynamic range and improving battery life by optimizing power amplifier performance across different output power levels.
Implementation Method 1
a DC-DC converter operates to control a variable supply voltage provided to the power amplifier circuitry, thereby controlling an output power level, or average output power, of the power amplifier circuitry
Data Source
AI summary
A system and method are provided for efficiently amplifying a radio frequency signal. In general, the system includes power amplifier circuitry that efficiently amplifies an input signal under power back-off conditions. In one embodiment, the power amplifier circuitry has an efficiency of at least 30% at a 6 dB back-off point. In addition, DC-DC conversion circuitry operates to control a variable supply voltage provided to the power amplifier circuitry, thereby controlling an output power level, or average output power, of the power amplifier circuitry.