Multilayer RF Filter Layout for Steep Attenuation in Compact Modules
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Solution Overview
Problem
Filter devices for radio frequency signals face challenges in reducing size while maintaining steep attenuation characteristics, as reducing height affects impedance and frequency of attenuation poles, leading to decreased steepness of attenuation characteristics.
Innovation Solution
A filter device with a multilayer dielectric substrate configuration, where coupling lines in different layers face each other, reducing impedance in the 'odd mode' and minimizing impedance change in the 'even mode', allowing for size reduction without deteriorating attenuation characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the height of the filter device is reduced, then the size of the filter device is reduced, but the impedance of the transmission line changes and the steepness of the attenuation characteristics decreases
Solution Approach 1:
The patent transitions from a planar single-layer configuration to a three-dimensional multilayer configuration. The first and second coupling lines are placed in different layers of the dielectric substrate, facing each other vertically. This vertical stacking arrangement reduces the horizontal footprint and overall size of the filter device while maintaining the electrical performance through controlled impedance design in the multilayer structure.
Solution Approach 2:
The patent modifies the impedance parameters by changing the configuration from a single-layer to a multilayer structure. By placing coupling lines in different layers and controlling their spacing and dimensions, the impedance characteristics are optimized to maintain steep attenuation poles even when the device height is reduced. The parameter optimization includes adjusting line widths, spacing between layers, and dielectric constant selection.
2Length of stationary object
If the distance between transmission line and ground electrode is shortened, then the height is reduced, but the impedance changes and frequency of attenuation pole changes
Solution Approach 1:
The patent uses vertical layering to reduce the horizontal distance between coupling lines while managing the vertical distance to ground electrodes. The multilayer configuration allows precise control over impedance by adjusting the thickness of dielectric layers and the positioning of ground electrodes in the vertical dimension, thereby maintaining accurate attenuation pole frequencies despite reduced overall height.
Solution Approach 2:
The dielectric substrate layers act as intermediaries between the coupling lines and ground electrodes. By carefully selecting and controlling the thickness and dielectric constant of these intermediate layers, the patent achieves precise impedance control and maintains stable attenuation pole frequencies even when the overall device height is reduced.
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 the reduction of filter device size while maintaining steep attenuation characteristics, ensuring effective signal attenuation in specific frequency bands.
Implementation Method 1
a first coupling line electrically connected to the input end, a second coupling line electrically connected to the output end... The first coupling line and the second coupling line are formed in layers different from a layer of the ground electrode... The first coupling line faces the second coupling line
Implementation Method 2
resonance occurs in the radio frequency signal propagated through the branch line and a Q value increases, so that attenuation characteristics can be made steep
Data Source
AI summary
A filter device (130) is formed between an input end (T1) and an output end (T2), and is configured to attenuate a radio frequency signal in a specific frequency band. The filter device (130) includes a dielectric substrate (140) having a multilayer structure, ground electrodes (GND1 and GND2) formed in the dielectric substrate (140), a first coupling line (132) electrically connected to the input end (T1), a second coupling line (134) electrically connected to the output end (T2), and a stub (133) connected to the first coupling line (132) and the second coupling line (134). The first coupling line (132) and the second coupling line (134) are formed in layers different from layers of the ground electrodes (GND1 and GND2). The first coupling line (132) and the second coupling line (134) are disposed in different layers so as to face each other.