Reactive RF Power Combiner for Wideband Outphasing Efficiency
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Solution Overview
Problem
Conventional outphasing power combining systems face challenges in achieving wide-bandwidth linear amplification and high average efficiency due to loss and reactive loading issues, particularly when dealing with large peak-to-average power ratios (PAPR).
Innovation Solution
A power combining and outphasing system utilizing a reactive combiner with four or more input ports and power amplifiers, where the combiner is designed with reactive elements having specific reactance values to provide ideally lossless power combining and substantially resistive loading over a wide output power range, allowing for high average efficiency even with large PAPR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an isolating combiner is used to combine constant-amplitude signals, then the loading impedance to each power amplifier is constant and interactions between amplifiers are eliminated, but power not delivered to the output is dissipated as heat in the isolation resistor leading to rapid degradation of efficiency as output power is decreased
Solution Approach 1:
A reactive element is introduced as an intermediary component between the power amplifiers and the combiner. This reactive element dynamically adjusts its reactance to compensate for the effective reactive loading caused by amplifier interactions, thereby maintaining desirable loading conditions without requiring power dissipation in isolation resistors
Solution Approach 2:
The system dynamically changes the reactance parameter of the reactive element based on operating conditions (output power level). By adjusting the reactance value, the system maintains optimal loading impedance for power amplifiers across varying output power levels, preventing efficiency degradation while eliminating the need for constant power dissipation
2Loss of energy
If a lossless reactive combiner is used to combine power, then power loss in the combiner is eliminated, but the reactive portions of the effective load admittances become large outside of a limited power range leading to efficiency loss and power amplifier degradation
Solution Approach 1:
The reactive element provides preliminary compensation for the reactive loading effects before they can degrade amplifier performance. By anticipating and counteracting the reactive admittance changes across the power range, the system prevents efficiency loss and amplifier degradation while maintaining lossless power combining
Solution Approach 2:
The system transitions from a static combiner design to a dynamic one where the reactive element's reactance can be adjusted in response to changing operating conditions. This dynamic adaptation allows the combiner to maintain optimal performance across a wide power range, preventing the reactive admittance from becoming excessively large
3Use of energy by moving object
If conventional outphasing is used to achieve linear amplification with high efficiency, then constant-amplitude signals can be synthesized with highly-efficient PAs, but the effective reactive loading on the PAs depends upon operating point leading to compensation imperfections over wide ranges
Solution Approach 1:
The system employs feedback mechanisms where the reactance of the reactive element is adjusted based on the operating point (output power level). This feedback loop ensures that compensation remains accurate across wide operating ranges, maintaining both high efficiency and adaptability to different power levels
Solution Approach 2:
The reactive element is configured to provide preliminary compensation for reactive loading effects across the expected operating range. By pre-configuring the compensation strategy, the system ensures high efficiency is maintained while being adaptable to wide power range variations
Data Source
AI summary
A power combining and outphasing system and related techniques for simultaneously providing both wide-bandwidth linear amplification and high average efficiency is described. Providing linear amplification encompasses the ability to dynamically control an RF output power level over a wide range while still operating over a wide frequency bandwidth. The system and techniques described herein also operate to maintain high efficiency across a wide range of output power levels, such that a high average efficiency can be achieved for highly modulated output waveforms.