Acoustic Wave Filter Shield Placement for Wire-Specific Coupling Reduction
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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 piezoelectric substrate having series-arm resonators on one main surface and a cap substrate with a shield covering part of its surface. The shield is positioned to overlap the wire connecting the series-arm resonator without overlapping the wire connecting the external connection terminal, thereby reducing coupling and deterioration of characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a shield is added to reduce coupling between the acoustic wave filter and other components, then the attenuation characteristic deteriorates, but the transmission characteristic improves
Solution Approach 1:
The shield is selectively positioned to overlap only with the second wire (connecting to series-arm resonator) while deliberately avoiding overlap with the first wire (connecting to parallel-arm resonator). This local differentiation in shielding coverage allows the shield to reduce coupling effects on the series-arm resonator path without introducing harmful coupling to the parallel-arm resonator path, thus improving transmission characteristic while maintaining attenuation characteristic.
2Object-affected harmful factors
If the shield overlaps both wires to maximize shielding effect, then coupling reduction is improved, but the complexity of the structure increases
Solution Approach 1:
Instead of providing complete shielding coverage over both wires, the invention applies partial shielding only to the second wire. This partial action is sufficient to reduce coupling effects on the series-arm resonator path without the need for comprehensive shielding, thereby reducing structural complexity while still achieving effective coupling reduction where most needed.
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 deterioration of both the transmission and attenuation characteristics of the acoustic wave filter by minimizing coupling between the filter components and external components.
Implementation Method 1
a piezoelectric substrate including a first main surface and a second main surface opposite to each other
Implementation Method 2
A shield is disposed at the third main surface. The shield at least partially overlaps the second wire without overlapping the first wire in plan view
Data Source
AI summary
An acoustic wave filter includes a piezoelectric substrate including a first main opposite to a second main surface. The first main surface includes two series-arm resonators disposed thereon. A cap substrate includes a third main surface facing the first main surface, and disposed to define a space between the first main surface and the third main surface. An external connection terminal is connected to the antenna connection terminal, and another external connection terminal is connected to an amplifier. A first wire that electrically connects the external connection terminal to one of the series-arm resonators, and a second wire that electrically connects the other external connection terminal to the other series-arm resonator are also included. A shield is disposed at the third main surface. The shield at least partially overlaps the second wire without overlapping the first wire in plan view.