Hybrid Chireix-Doherty Amplifier With Dynamic Load Modulation
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Solution Overview
Problem
Conventional power amplifiers struggle to achieve high efficiency and output power simultaneously, particularly in radio transmitters for broadcast, cellular, and satellite systems, due to limitations in amplifier structures like Doherty and Chireix amplifiers.
Innovation Solution
A hybrid Chireix-Doherty amplifier design that incorporates a main amplifier operating in inverse class F mode and an auxiliary amplifier in class C mode, configured in a push-pull topology, with optimized input and output matching networks and a combiner network, to enhance power output and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional Doherty or Chireix amplifier structures are used, then the amplifier can operate with reasonable efficiency, but the output power is limited and complexity increases
Solution Approach 1:
The patent combines the Doherty amplifier structure and Chireix outphasing system into a hybrid architecture that integrates the impedance-inverting quarter wave line from Doherty with the constant amplitude operation and differential phase-shift control from Chireix. This merging allows the amplifier to achieve higher output power (1.75× increase) while maintaining efficiency across a wide power range, resolving the contradiction between power output and structural complexity
2Power
If amplifier power output is increased, then more power is delivered to the load, but efficiency decreases due to power loss
Solution Approach 1:
The patent employs dynamic impedance transformation through the impedance-inverting quarter wave line that adapts the load impedance seen by the main amplifier based on the operating point. The auxiliary amplifier dynamically modulates the impedance to maintain optimal operating conditions across different power levels, enabling the system to achieve 75% drain efficiency even at 3 dB power back-off while delivering high output power
3Loss of energy
If amplifier efficiency is improved, then power consumption is reduced, but output power capability is limited
Solution Approach 1:
The patent segments the amplification function into a main amplifier operating in inverse class F mode for high efficiency and an auxiliary amplifier operating in class C mode for power boosting. The main amplifier handles the fundamental frequency with high efficiency, while the auxiliary amplifier provides additional power capability through impedance modulation. This segmentation allows the system to achieve both high efficiency (75% drain efficiency) and high output power capability simultaneously
Data Source
AI summary
In some examples, a hybrid Chireix-Doherty amplifier comprises a first and second input network, a main amplifier coupled to a first output of the first input network, an auxiliary amplifier coupled to a second output of the second input network, and a combiner network. The combiner network is coupled to a first output of the main amplifier and an output of the auxiliary amplifier. The combiner network includes an output node for coupling to a load, e.g., an antenna of a base station for a radio network. The main amplifier is implemented as an inverse class-F amplifier.