Bandpass Filter Resonator Structure for High-Frequency Attenuation
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Solution Overview
Problem
Existing bandpass filters face challenges in achieving high attenuation at higher frequencies and miniaturization with low insertion loss, due to electromagnetic coupling and variations in filtering characteristics caused by lateral displacement of resonance lines in layered structures.
Innovation Solution
The bandpass filter design reduces parasitic inductance by directly connecting input/output terminals to resonance capacitances, uses via-conductors as inductors to shorten resonance lines, and employs a coupling capacitance with opposing capacitance electrodes on different dielectric layers, separated by a ground electrode to minimize parasitic capacitance and electromagnetic coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If resonance lines are constituted by pluralities of transmission lines to achieve miniaturization, then the filter size is reduced, but electromagnetic coupling increases causing increased insertion loss
Solution Approach 1:
A ground electrode is introduced as an intermediary between the resonance lines and the capacitance electrodes. This ground electrode shields the resonance lines from direct electromagnetic coupling with the capacitance electrodes, reducing parasitic capacitance and insertion loss while allowing the resonance lines to be closely spaced for miniaturization
Solution Approach 2:
The filter structure is segmented into distinct functional layers: resonance lines on one dielectric layer, ground electrode on an intermediate layer, and capacitance electrodes on another layer. This segmentation allows independent optimization of each component's position and reduces unwanted electromagnetic interactions
2Ease of manufacture
If via-conductors are used to connect resonance lines to capacitance electrodes, then the filter can be constructed in a laminate structure, but parasitic inductance increases reducing high-frequency attenuation
Solution Approach 1:
The ground electrode acts as an intermediary that provides a low-inductance return path for high-frequency currents. By placing the ground electrode between the resonance lines and capacitance electrodes, it shields the parasitic inductance of via-conductors from affecting the resonance circuit's high-frequency behavior, maintaining effective attenuation
Solution Approach 2:
The problem is solved by transitioning from a two-dimensional planar connection to a three-dimensional layered structure. The ground electrode on an intermediate layer provides electromagnetic shielding in the vertical dimension, isolating the resonance lines from parasitic effects of via-conductor connections
3Device complexity
If capacitance electrodes are arranged on the same dielectric layer as resonance lines, then the structure is simplified, but parasitic capacitance increases affecting filtering characteristics
Solution Approach 1:
The dielectric structure is segmented into multiple layers with distinct functions: resonance lines on one layer, ground electrode on an intermediate layer, and capacitance electrodes on another layer. This segmentation physically separates elements that should be electrically isolated, reducing parasitic capacitance while maintaining manufacturing simplicity through standardized laminate construction
Solution Approach 2:
A ground electrode is placed as an intermediary between the resonance lines and capacitance electrodes on adjacent dielectric layers. This ground electrode shields the electric field between resonance lines and capacitance electrodes, minimizing parasitic capacitance and stabilizing filtering characteristics
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 design achieves high attenuation not only near the passband but also at higher frequencies, while allowing for miniaturization and reduced variation in filtering characteristics due to lateral displacement, resulting in improved bandwidth and reduced insertion loss.
Implementation Method 1
This structure reduces the length of via-conductors from the input/output terminals to the resonance capacitances, thereby reducing parasitic inductance to the resonance capacitances when viewed from the input/output terminals
Implementation Method 2
a laminate-type bandpass filter constituted by a laminate substrate comprising pluralities of dielectric layers provided with conductor patterns, which comprises three or more resonators between two input/output terminals. Each resonator is constituted by a resonance line and a resonance capacitance connected to one end of the resonance line
Implementation Method 3
the resonance lines and the capacitance electrodes are arranged on different dielectric layers from each other with a ground electrode interposed therebetween. The bandpass filter has high attenuation at higher frequencies than the passband, with the resonance capacitances having impedance close to short-circuiting
Implementation Method 4
The bandpass filter has high attenuation at higher frequencies than the passband, with the resonance capacitances having impedance close to short-circuiting
Data Source
Figure 1(a)
Figure 1(b)~1(d)
Figure 2~7
AI summary
A bandpass filter comprising two or more resonators arranged between two input/output terminals in a laminate substrate comprising pluralities of dielectric layers; each resonator being constituted by a resonance line and a resonance capacitance connected to one end of the resonance line; capacitance electrodes forming said resonance capacitances and said resonance lines being arranged on different dielectric layers, via a planar ground electrode covering the entire structural portion of the bandpass filter when viewed in a lamination direction; and in each of the resonators connected to said two input/output terminals, the junctions of said input/output terminals to said paths between said resonance lines and said resonance capacitances being closer to said resonance capacitances than said resonance lines in a lamination direction.