Distributed Power Amplifier Layout for Broadband Impedance Matching
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Solution Overview
Problem
Existing distributed power amplifiers face challenges in achieving high efficiency over a wide frequency band due to narrow-band frequency characteristics, load modulation, and increased parasitic capacitance, which impairs broadband performance and makes it difficult to maintain high-efficiency matching.
Innovation Solution
A distributed power amplifier configuration with a main amplifier and (N-1) auxiliary amplifiers, where the auxiliary amplifiers start operation after the main amplifier reaches a predetermined power level, and (N-1) stages of transmission lines with different characteristic impedances are used to connect the main and auxiliary amplifiers, allowing for asymmetric power distribution and impedance matching across the operating power range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single λ/4 length transmission line is used to connect main amplifier and auxiliary amplifier group, then the combining circuit achieves simple structure, but the frequency characteristic becomes narrow-band and broadband performance deteriorates
Solution Approach 1:
The patent divides the single transmission line into multiple transmission lines with different electrical lengths (θ1, θ2, ..., θN-1). Each transmission line is connected to a different auxiliary amplifier, creating a segmented approach to impedance transformation that works across multiple frequency points within the broadband range.
Solution Approach 2:
Each transmission line is designed with specific electrical length and characteristic impedance tailored to its associated auxiliary amplifier's output power ratio. This local optimization ensures that each amplifier-contributing frequency component achieves proper impedance matching at the combining node, maintaining high efficiency across the entire broadband spectrum.
2Use of energy by moving object
If auxiliary amplifiers start operation before main amplifier saturation, then load modulation occurs and efficiency improves at back-off, but impedance matching becomes difficult to maintain across wide frequency band
Solution Approach 1:
The patent transforms the fixed impedance transformation approach into a variable one by assigning different electrical lengths to different transmission lines. This parameter variation allows the system to maintain proper impedance matching across multiple frequency points while enabling auxiliary amplifiers to operate in a way that improves back-off efficiency without sacrificing broadband performance.
3Ease of operation
If same-size amplifying elements are used for main and auxiliary amplifiers, then device uniformity is achieved, but parasitic capacitance increases and broadband high-efficiency matching becomes difficult
Solution Approach 1:
The patent introduces asymmetry in the transmission line design by assigning different electrical lengths (θ1 > θ2 > ... > θN-1) to different auxiliary amplifiers based on their output power ratios. This asymmetric approach compensates for the parasitic effects and power distribution differences, enabling high-efficiency broadband matching that would be difficult to achieve with uniform amplifier elements alone.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enables high-efficiency operation across a wide frequency band by suppressing load modulation and optimizing impedance matching, reducing parasitic capacitance effects and enhancing broadband characteristics.
Implementation Method 1
a first to (N-1)-th transmission lines 141 to 145 having different electrical lengths from one another and having different characteristic impedances from one another are connected in series with one another
Implementation Method 2
enables high-efficiency operation across a wide frequency band by suppressing load modulation and optimizing impedance matching
Implementation Method 3
reducing parasitic capacitance effects and enhancing broadband characteristics
Data Source
AI summary
A distributed power amplifier includes a two-divider that divides an input signal into two signals, a main amplifier that amplifies one of the two signals, (N-1) dividers that divide another of the two signals into (N-1) signals, (N-1) auxiliary amplifiers that amplify (N-1) signals, and (N-1) stages of transmission lines connected in series with one another. An output end of the main amplifier is connected to an end portion on an input side of a first-stage transmission line. Output ends of the (N-1) auxiliary amplifiers are connected to end portions on an output side of the (N-1) stages of transmission lines, respectively. The (N-1) auxiliary amplifiers include an auxiliary amplifier having a maximum output voltage that is larger than maximum output power of the main amplifier.