Multi-Branch Power Amplifier Combining for Wide Power Back-Off
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Solution Overview
Problem
Conventional power amplifier circuits experience efficiency depression when a large power back-off range is implemented, leading to reduced efficiency and increased load-pull ratios, which limit the bandwidth and power handling capabilities of the amplifier.
Innovation Solution
The proposed power amplifier circuit employs a multi-branch architecture with cascaded amplifiers and matching networks, along with coupled lines to form combiners, which series-combine power from multiple branches, reducing the load impedance and achieving higher efficiency across a wider power back-off range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a conventional class-AB power amplifier is used, then the amplifier can operate in a high-power back-off state, but the efficiency decreases significantly when the power back-off range increases
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 the system to maintain high efficiency across a wide power back-off range by selectively activating appropriate branches based on the required output power level.
Solution Approach 2:
The patent transitions from a single-branch architecture to a multi-branch architecture with series combiners, adding a dimensional aspect to the power combination. The series combiner configuration transforms the way power is aggregated, enabling efficient operation across extended back-off ranges by utilizing multiple operational dimensions simultaneously.
2Adaptability or versatility
If a larger power back-off range is implemented, then the amplifier can handle varying power levels, but an efficiency depression area appears with larger depression
Solution Approach 1:
Different branches are designed with specific local characteristics optimized for different power levels. The first and second amplifiers in the first branch are configured with specific matching networks and coupling coefficients optimized for certain operating conditions, while the third and fourth amplifiers in the second branch have different optimizations. This local quality differentiation eliminates the efficiency depression area by ensuring each branch operates at optimal efficiency in its designated power range.
Solution Approach 2:
The system dynamically switches between different branch configurations based on the required power level. The series combiner architecture enables dynamic reconfiguration of the power paths, allowing the amplifier to adapt its internal structure to maintain high efficiency across the entire power back-off range, eliminating static efficiency limitations.
3Power
If multiple branches are combined using conventional combiners, then power can be aggregated, but the load impedance increases leading to higher load-pull ratios
Solution Approach 1:
Instead of using conventional parallel combiners that increase load impedance, the patent employs series combiners that invert the combination approach. The series connection of the first and second coupled lines, and the third and fourth coupled lines, transforms the impedance characteristics, resulting in lower load-pull ratios while maintaining high output power capability.
Data Source
AI summary
A power amplifier circuit includes: a first branch, including a first amplifier and a first matching network cascaded; a second branch, including a second amplifier and a second matching network 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 cascaded; and a fourth branch, including a fourth amplifier and a fourth matching network 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.