Coupler with Segmented Resistive Film for Signal Attenuation
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Solution Overview
Problem
Conventional couplers with integrated resistor elements for attenuating signals suffer from significant frequency-dependent attenuation due to the skin effect, leading to high-frequency loss and increased contact resistance between conductive and resistive films, which complicates circuit design, especially in broadband wireless communication devices.
Innovation Solution
The coupler design features a substrate with a main line and a sub line where the resistive film is partially exposed, allowing the conductive film to be free from full coverage, reducing contact resistance and frequency-dependent attenuation by ensuring the resistive film contacts the conductive film only at upper and end surfaces, and using an insulating film to prevent oxidation and enhance adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the resistive film is formed on the entire surface of the substrate including below the conductive film, then the manufacturing process is simplified, but the skin effect causes significant frequency-dependent attenuation and high-frequency loss
Solution Approach 1:
The resistive film is segmented into a bridge portion that contacts the conductive film and non-bridge portions that do not contact the conductive film. This segmentation allows the resistive film to provide attenuation only where needed (at the bridge portion) while avoiding the skin effect problems that occur when the resistive film is present below the entire conductive film structure.
Solution Approach 2:
The resistive film is positioned to have different functions in different locations: at the bridge portion, it provides attenuation and impedance control by contacting the conductive film, while in non-bridge portions, it is removed or not formed to prevent frequency-dependent attenuation. This local differentiation resolves the contradiction between manufacturing simplicity and performance.
2Loss of energy
If the resistive film contacts the conductive film only at the end surface, then the frequency-dependent attenuation is reduced, but the contact resistance increases significantly
Solution Approach 1:
The contact between the resistive film and conductive film is extended from a single-point end surface contact to a multi-dimensional contact involving both the upper surface and end surface of the conductive film. This dimensional expansion of the contact area reduces contact resistance while maintaining the benefit of reduced frequency-dependent attenuation compared to full surface contact.
3Stability of the object's composition
If the conductive film is fully covered by the resistive film, then the impedance control is improved, but the contact resistance between conductive and resistive films increases
Solution Approach 1:
Instead of fully covering the conductive film with the resistive film (excessive action), the resistive film is applied partially only at the bridge portion where impedance control is needed. This partial application maintains adequate impedance control while minimizing the contact area and thus reducing contact resistance between the conductive and resistive films.
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 reduces frequency-dependent attenuation and contact resistance, stabilizes high-frequency characteristics, and prevents resistive film degradation, resulting in improved performance and reliability for wireless communication devices.
Implementation Method 1
A current signal is attenuated more significantly in the resistive film than in the conductive film
Implementation Method 2
The flowing of the current signal in the resistive film is caused by so-called a skin effect. The skin effect has frequency characteristics, so that the attenuation amount differs depending on a frequency of the current signal.
Implementation Method 3
the resistive film is covered by the insulating film before the formation of the conductive film, thereby making it possible to prevent the resistive film from being oxidized during a manufacturing process
Data Source
AI summary
A coupler includes an input terminal and an output terminal which are provided on a substrate, a main line provided on the substrate and having one end connected to the input terminal and the other end connected to the output terminal, and a sub line including a conductive film and a resistive film which are provided on the substrate and electromagnetically coupled to the main line at a part of the conductive film. The conductive film has wiring patterns. The resistive film includes a resistive film pattern having an end portion fitted into between the wiring pattern and substrate and an end portion fitted into between the wiring pattern and substrate. The end portions and each contact the conductive film at least at its upper surface and end surface.