Multi-Branch Power Amplifier Combining for Back-Off Efficiency
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Solution Overview
Problem
Conventional power amplifiers experience efficiency depression in large power back-off ranges, leading to reduced performance and increased load-pull ratios, which limits their effectiveness in high-power and high-bandwidth applications.
Innovation Solution
The power amplifier circuit design incorporates multiple branches with cascaded amplifiers and matching networks, coupled lines forming combiners, which series-combine power and reduce load impedance, enabling higher efficiency and lower load-pull ratios, particularly at increased power back-off ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional class-AB power amplifier is used, then simplicity of structure is maintained, but efficiency in power back-off state is much lower than in peak value state
Solution Approach 1:
The power amplifier is divided into multiple branches (first branch with first amplifier, second branch with second amplifier, third branch with third amplifier, fourth branch with fourth amplifier), each handling different power levels. This segmentation allows efficient operation at different back-off states while maintaining overall system efficiency.
Solution Approach 2:
Multiple amplifier branches are combined through coupled lines forming combiners (first combiner from first and second branches, second combiner from third and fourth branches). The combiners merge the output signals to achieve high efficiency across the full power range including back-off states.
2Loss of energy
If Doherty or outphasing technology is used to improve efficiency, then efficiency in power back-off is improved, but efficiency depression area appears when power back-off range is large
Solution Approach 1:
The amplifier is segmented into four branches that can be independently controlled, with each branch optimized for specific power levels. This allows the system to maintain high efficiency across a wide back-off range (up to 10 dB or more) without efficiency depression areas.
Solution Approach 2:
The amplifier dynamically switches between different branch configurations based on the input signal power level. At peak power, all branches are active; at back-off states, fewer branches are active, dynamically adapting to maintain optimal efficiency across the entire operating range.
3Adaptability or versatility
If power back-off range is increased, then adaptability to high peak-to-average ratio signals is improved, but efficiency depression increases
Solution Approach 1:
The four-branch architecture segments the power handling capability, with each branch optimized for specific power levels. This enables the amplifier to handle signals with peak-to-average ratios of 10 dB or higher while maintaining high efficiency throughout the back-off range without efficiency depression.
4Power
If series combiner is used to reduce load impedance, then ease of implementing high-power amplifier is improved, but device complexity increases
Solution Approach 1:
The series combiner merges the output of the first and second combiners, connecting them in series to achieve impedance transformation. This reduces the load impedance presented to each amplifier branch, enabling high-power operation while distributing the complexity across modular combiner stages.
Data Source
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AI summary
A power amplifier circuit is provided, to improve efficiency of a power amplifier. The circuit includes: a first branch, including a first amplifier and a first matching network that are cascaded; a second branch, including a second amplifier and a second matching network that are cascaded, where a first coupled line enables the first branch and the second branch to form a first combiner; a third branch, including a third amplifier and a third matching network that are cascaded; and a fourth branch, including a fourth amplifier and a fourth matching network that are cascaded, where a second coupled line enables the third branch and the fourth branch to form a second combiner. A first output end of the first coupled line is a signal output end of the circuit, and a second output end of the first coupled line is connected to a first output end of the second coupled line, to enable the first combiner and the second combiner to form a series combiner.