Multilayer Power Divider Stubs for Impedance Matching
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Solution Overview
Problem
Wilkinson power dividers/combiners formed on multilayer boards face issues with reflection characteristics and isolation due to impedance discontinuity caused by vias, leading to deteriorated performance in high-frequency signal handling.
Innovation Solution
Incorporating a quarter-wave impedance transformer and an isolation resistor connected by a transmission line with a length that is an integer multiple of half a wavelength, and adding stubs between the transmission line and input/output terminals to mitigate impedance discontinuity effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a quarter-wave impedance transformer is used to connect the common terminal and input/output terminals, then the power divider/combiner achieves proper impedance matching and signal division, but impedance discontinuity occurs at via portions in multilayer board structures, causing deteriorated reflection characteristics and isolation
Solution Approach 1:
The transmission line connecting the isolation resistor to input/output terminals is segmented into multiple sections with different characteristic impedances. This segmentation allows each section to be optimized for different portions of the signal path, compensating for the impedance discontinuity introduced by via holes in the multilayer board structure.
Solution Approach 2:
Different sections of the transmission line are assigned different characteristic impedances based on their local requirements. The first line has a first characteristic impedance and the second line has a second characteristic impedance, allowing each portion to be tailored for optimal performance in its specific location within the multilayer structure.
2Adaptability or versatility
If the board thickness increases and strip conductor pattern is arranged deeper in inner layer, then the multilayer board structure provides better isolation and stacking capability, but the electrical length of via and impedance discontinuity cannot be ignored, causing deteriorated reflection characteristics
Solution Approach 1:
Stub elements are introduced as intermediary components between the transmission line and ground. These stubs act as compensating elements that counterbalance the adverse effects of via hole impedance discontinuity and electrical length, restoring proper impedance matching without requiring changes to the fundamental multilayer stacked structure.
Solution Approach 2:
The characteristic impedances of different transmission line sections are specifically designed with different values (first characteristic impedance vs. second characteristic impedance) to compensate for the cumulative effect of via hole discontinuities. This parameter variation allows the system to maintain performance despite increased board thickness and deeper conductor placement.
3Adaptability or versatility
If a transmission line with integer multiple of half wavelength is used between input/output terminal and isolation resistor, then the phase difference achieves odd multiple of 180 degrees for improved design freedom, but impedance discontinuity at via portion still causes deteriorated isolation between input/output terminals
Solution Approach 1:
The transmission line design incorporates dynamic compensation through stub elements that can be adjusted in length and position. This allows the system to dynamically compensate for impedance discontinuity effects across different operating conditions while maintaining the beneficial odd multiple of 180 degrees phase difference for isolation.
Solution Approach 2:
The transmission path is constructed as a composite structure combining multiple transmission line sections with different characteristic impedances and stub elements. This composite approach allows simultaneous achievement of the required phase difference for design freedom and impedance matching for terminal isolation.
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
The solution enhances reflection characteristics and isolation between terminals, suitable for small and stacked multilayer board structures, maintaining satisfactory performance across the frequency range.
Implementation Method 1
The common terminal and each input/output terminal are connected to each other by a quarter-wave (λ/4) impedance transformer
Implementation Method 2
a phase difference between a route that connects two input/output terminals via two quarter-wave impedance transformers and a route that connects two input/output terminals via an isolation resistor (absorption resistor) is an odd multiple of 180 degrees
Implementation Method 3
The input/output terminals are connected to each other via one isolation resistor called an absorption resistor
Data Source
Figure 1~3
Figure 2A~2C
Figure 4A~4B
AI summary
Provided is a power divider/combiner capable of improving reflection characteristics and isolation characteristics. The power divider/combiner is formed by a multilayer board, and a strip conductor is arranged in an inner layer of the multilayer board and a chip resistor is arranged on an outer surface of the multilayer board. The power divider/combiner includes vias, which connect the strip conductor and the chip resistor, and includes stubs mounted between input/output terminals and the vias. With this configuration, it is possible to adjust induction mainly during an odd mode of an even/odd mode operation and to consequently improve reflection characteristics of the input/output terminals and isolation characteristics between the input/output terminals.