Acoustic Wave Filter Shield Layout for Coupling Without Parasitic Capacitance
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Solution Overview
Problem
Existing technologies fail to effectively reduce deterioration of both the transmission and attenuation characteristics of acoustic wave filters due to coupling with other components.
Innovation Solution
The acoustic wave filter is designed with a shield that covers a part of the side surface of the substrate, specifically excluding areas opposing certain wires to minimize parasitic capacitance and coupling, thereby reducing deterioration of transmission and attenuation characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a shield covers the entire side surface of the substrate, then coupling between the acoustic wave filter and other components is reduced, but parasitic capacitance increases causing deterioration of transmission characteristic
Solution Approach 1:
The shield is configured to cover only specific regions of the substrate side surface - specifically the regions opposing the series-arm resonators - while leaving regions opposing the wires uncovered. This local differentiation allows the shield to reduce coupling with resonators while avoiding parasitic capacitance with wires, thereby resolving the contradiction between reducing harmful coupling and maintaining transmission characteristics.
2Object-affected harmful factors
If a shield is added to reduce coupling, then attenuation characteristic deteriorates, but without shield transmission characteristic deteriorates due to coupling
Solution Approach 1:
The shield selectively covers regions opposing the series-arm resonators while excluding regions opposing the wires. This localized shielding approach reduces coupling with resonators (improving attenuation characteristic) while avoiding parasitic capacitance with wires (maintaining transmission characteristic), thus resolving the contradiction without sacrificing either performance parameter.
3Object-affected harmful factors
If the shield covers the area opposing the wire, then coupling is reduced, but parasitic capacitance increases causing transmission characteristic deterioration
Solution Approach 1:
The shield is designed to exclude coverage of the region opposing the wire, thereby preventing parasitic capacitance formation between the shield and wire. This local exclusion strategy maintains transmission characteristic while the shield still provides coupling reduction in other critical regions, resolving the contradiction between coupling reduction and transmission quality.
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 effectively reduces the deterioration of both transmission and attenuation characteristics by minimizing parasitic capacitance and coupling, thus enhancing the overall performance of the acoustic wave filter.
Implementation Method 1
the shield covers at least a part of a second area of a side surface of the first substrate opposing the second wire without covering a first area of the side surface of the first substrate opposing the first wire
Implementation Method 2
capacitive coupling and/or inductive coupling between the radio frequency filter and the shield case is reduced
Data Source
AI summary
An acoustic wave filter includes a piezoelectric substrate, series-arm resonators disposed at the piezoelectric substrate, an external connection terminal disposed at the piezoelectric substrate and connected to an antenna connection terminal, an external connection terminal disposed at the piezoelectric substrate and connected to an amplifier, a wire disposed at the piezoelectric substrate and electrically connecting the external connection terminal to the series-arm resonator, a wire disposed at the piezoelectric substrate and electrically connecting the external connection terminal to the series-arm resonator, and a shield that covers a part of a side surface of the piezoelectric substrate, wherein the shield covers at least a part of an area of the side surface of the piezoelectric substrate opposing the wire without covering an area of the side surface of the piezoelectric substrate opposing the wire.