RF Power Amplifier Voltage Control for Efficiency and Linearity
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Solution Overview
Problem
RF communication systems face a trade-off between energy efficiency and linearity, typically achieving either high efficiency or high linearity but not both simultaneously in RF amplifiers and transmitters.
Innovation Solution
The implementation of digital control over the amplitudes and phases of RF input signals and supply voltages in RF power amplifiers, using non-linear power amplifiers and dynamic selection of discrete voltage levels based on data samples within a window, to achieve high efficiency and linearity simultaneously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If non-linear power amplifiers are used to achieve high power efficiency, then energy efficiency is improved, but linearity deteriorates
Solution Approach 1:
The data stream is segmented into a window of Nw samples, and voltage level decisions are made based on this segmented window rather than individual samples. This segmentation allows the system to achieve linearity through averaging effects while maintaining the efficiency benefits of non-linear amplifiers operating at higher power levels.
Solution Approach 2:
The system dynamically selects from a plurality of discrete voltage levels based on the content of the data window. This dynamic voltage control allows the amplifier to adapt its operating point, achieving both high efficiency through non-linear operation and improved linearity through intelligent voltage selection and backoff techniques.
2Manufacturing precision
If digital control is applied to maintain linearity, then linearity is improved, but device complexity increases
Solution Approach 1:
The system changes the voltage parameter from a continuous range to a discrete set of levels. This parameter quantization simplifies the control complexity while maintaining acceptable linearity performance. The controller selects from predetermined voltage levels based on the data window content, avoiding the need for complex continuous control mechanisms.
3Manufacturing precision
If backoff is applied to achieve desired output power level, then linearity is improved, but power efficiency deteriorates
Solution Approach 1:
The system applies partial backoff by selecting from discrete voltage levels that provide sufficient but not excessive power margin. Rather than consistently operating with large backoff margins, the system uses just enough voltage headroom to maintain linearity while minimizing efficiency loss. This partial action approach optimizes the trade-off between linearity and efficiency.
Data Source
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AI summary
A radio frequency (RF) power amplifier system or transmitter includes one or more power amplifiers and a controller that is configured to adjust amplitudes and phases of RF input signals of the one or more power amplifiers and supply voltages applied to the one or more power amplifiers. In embodiments where multiple power amplifiers are used, a combiner may be provided to combine outputs of the power amplifiers. In at least one implementation, amplitude adjustment of the RF input signals of the one or more power amplifiers may be used to provide transmit power control and/or power backoff.