Capacitive Resonator Filter Layout for Low-Height Q Retention
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Solution Overview
Problem
Existing filters face a challenge in reducing height without deteriorating their characteristics, particularly in terms of frequency response and Q-factor.
Innovation Solution
The filter design incorporates a dielectric substrate with shielding conductors on opposite surfaces and resonators connected via via electrodes, utilizing capacitive coupling structures where electrode patterns overlap to maintain effective coupling while reducing height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the height of the filter is simply reduced, then the height is reduced, but the filter characteristics deteriorate
Solution Approach 1:
The patent transitions from traditional lateral coupling between resonators to vertical capacitive coupling by overlapping electrode patterns in the height direction. This dimensional change allows coupling to occur along the Z-axis (vertical direction) rather than requiring lateral separation, enabling height reduction while maintaining coupling effectiveness and filter characteristics.
Solution Approach 2:
The patent optimizes the distance parameter between the capacitor electrode and capacitive coupling structure, specifying that the distance should be less than or equal to twice the distance between the shielding conductor and capacitor electrode. This parameter control ensures strong capacitive coupling while maintaining compact vertical dimensions, resolving the contradiction between height reduction and characteristic preservation.
2Loss of energy
If the distance between capacitor electrode and capacitive coupling structure is increased, then the coupling is weakened, but the Q-factor is improved
Solution Approach 1:
The patent establishes an optimal parameter range for the distance between the capacitor electrode and capacitive coupling structure (less than or equal to twice the shielding conductor to capacitor electrode distance). This parameter optimization balances coupling strength and Q-factor by preventing excessive coupling that would lower Q-factor while maintaining sufficient coupling for filter operation.
Solution Approach 2:
The patent introduces a shielding conductor as an intermediary element between the capacitor electrode and the capacitive coupling structure. This shielding conductor enables capacitive coupling through its electric field while maintaining physical separation, thus achieving strong coupling without direct contact that would compromise Q-factor.
3Length of stationary object
If the filter height is reduced, then the compactness is improved, but the resonator performance deteriorates
Solution Approach 1:
The patent repositions the coupling mechanism from the horizontal plane to the vertical dimension by using overlapping electrode patterns. This allows the resonator structure to maintain its horizontal footprint while reducing vertical height, preserving resonator performance through proper capacitive coupling in the Z-direction.
Solution Approach 2:
The patent implements a nested structure where the capacitive coupling structure is positioned within the vertical space above or below the capacitor electrode, rather than requiring lateral expansion. This nested arrangement in the vertical dimension enables compact height while maintaining the resonator's horizontal performance 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 a reduction in filter height while preserving satisfactory frequency characteristics and Q-factor, ensuring optimal performance.
Implementation Method 1
a capacitor electrode (18, 19) facing toward the first shielding conductor (12A) and connected to one end of the via electrode portion (20), and a capacitive coupling structure (71) including a first electrode pattern (19A3) connected to the first capacitor electrode (19A)
Implementation Method 2
at least a portion of the second electrode pattern (18B2) overlapping with at least a portion of the first electrode pattern (19A3) as viewed in plan
Data Source
AI summary
A filter is provided with: a plurality of resonators each comprising a via-electrode portion formed in a dielectric substrate, and a capacitor electrode that faces a first shielding conductor and is connected to one end of the via-electrode portion; and a first capacitively coupled structure which includes a first electrode pattern connected to the first capacitor electrode of the first resonator), and a second electrode pattern which is connected to the second capacitor electrode of the second resonator and of which at least a part overlaps at least a part of the first electrode pattern in plan view.