Envelope-Tracking RF Power Amplifier for Class F Linearity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Radio frequency power amplifiers face a trade-off between high efficiency and linearity, with class F and inverse class F operations experiencing poor linearity and narrow dynamic range, respectively, due to harmonic distortion and saturation issues, which affect energy efficiency and signal processing.
Innovation Solution
A radio frequency power amplifier design featuring first and second amplifier stages coupled in series, one operating in class F and the other in inverse class F, with an envelope detector and power supply that adjusts the electrical supply voltage to follow the input signal's envelope, ensuring consistent saturation levels and maintaining operation across varying input signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If class F operation is used to achieve high efficiency, then power efficiency is improved, but linearity deteriorates due to harmonic distortion
Solution Approach 1:
The amplifier is divided into multiple stages with different classes (class F and inverse class F stages), where each stage handles specific harmonic functions. This segmentation allows the system to achieve high efficiency through class F operation while maintaining linearity through the complementary inverse class F stage that processes harmonic distortion components separately.
Solution Approach 2:
Harmonic traps are introduced as intermediary elements between the amplifier stages and the load. These traps selectively filter harmonic frequencies, preventing them from distorting the output signal. The traps act as mediators that allow the amplifier to operate in efficient class F mode while removing the harmful harmonic distortion that would otherwise degrade linearity.
2Use of energy by moving object
If inverse class F operation is used to achieve high efficiency, then power efficiency is improved, but dynamic range is reduced due to saturation issues
Solution Approach 1:
The patent combines inverse class F operation with class F operation in a multi-stage configuration. The inverse class F stage provides high efficiency operation, while the class F stage compensates for the narrow dynamic range limitation. By merging these complementary approaches, the system achieves both high efficiency and extended dynamic range that neither stage could achieve alone.
Solution Approach 2:
The amplifier employs dynamic supply voltage control where the supply voltage is adjusted according to the input signal envelope. This dynamic adjustment allows the amplifier to maintain optimal saturation levels across varying signal conditions, effectively expanding the dynamic range while preserving the high efficiency benefits of inverse class F operation.
3Device complexity
If fixed supply voltage is used in class F amplifier, then circuit simplicity is maintained, but performance degrades under varying input signal conditions
Solution Approach 1:
The patent implements dynamic supply voltage control where the supply voltage to the amplifier stages is modulated according to the envelope of the input signal. This dynamic adjustment ensures that the amplifier maintains consistent saturation levels and optimal performance across the entire dynamic range of input signals, rather than relying on a fixed supply voltage that would result in performance degradation under varying conditions.
Data Source
AI summary
A radio frequency power amplifier has first and second amplifier stages coupled in series, one of which is operated in class F and the other is operated in inverse class F; an envelope detector adapted to detect an envelope of the input signal; a power supply coupled to supply an electrical supply voltage to the first and second amplifier stages, wherein the electrical supply voltage is controlled to follow the envelope of the input signal. Such amplifier makes it possible to maintain class F and inverse class F operation, respectively, of the first and second amplifier stages independent on the input signal. Preferably, this is done by controlling the electrical supply voltage so that the saturation levels of the first and second amplifier stages follow the envelope of the input signal.