Coupled Resonator Filter Border Ring Layout for Spurious Mode Suppression
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Solution Overview
Problem
Conventional coupled resonator filters suffer from spurious modes that degrade their performance, as design changes intended to suppress these modes in surface acoustic wave and bulk acoustic wave filters do not effectively translate to coupled resonator filters due to different operating characteristics.
Innovation Solution
Incorporating both a first and a second border ring, strategically placed on electrodes and intervening layers, to acoustically couple resonators and suppress spurious modes, thereby enhancing the filter's performance without significantly increasing insertion loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional surface acoustic wave and bulk acoustic wave filter design changes are applied to coupled resonator filters, then spurious modes may be suppressed in conventional filters, but spurious modes continue to degrade coupled resonator filter performance due to different operating characteristics
Solution Approach 1:
The patent applies parameter changes by modifying the physical and material properties of the resonators and their coupling structure. Specifically, it adjusts the piezoelectric layer thickness, electrode configuration, and coupling layer properties to alter the resonant characteristics and suppress spurious modes that conventional filter designs cannot address due to the different operating principles of coupled resonator filters.
Solution Approach 2:
The patent introduces an intermediary coupling layer between the first and second resonators that mediates their acoustic interaction. This intermediate structure enables controlled acoustic coupling while providing a mechanism to suppress spurious modes through its specific material composition and thickness, which acts as a buffer between the resonators' electromagnetic and acoustic fields.
2Reliability
If border rings are added to suppress spurious modes, then filter performance is improved, but device complexity increases
Solution Approach 1:
The border rings in the patent serve multiple functions simultaneously: they act as acoustic reflectors to suppress spurious modes, provide mechanical support for the piezoelectric layers, and define the geometric boundaries of the resonators. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity while achieving spurious mode suppression.
Solution Approach 2:
The patent merges the border ring structure with the existing electrode and piezoelectric layer configurations. The border rings are integrated into the resonator assembly such that they share common fabrication processes and structural support systems, combining multiple functions into a unified structure rather than adding separate independent components.
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
The implementation effectively reduces spurious modes and improves the overall performance of coupled resonator filters by adjusting the mass distribution and placement of border rings, moving border ring modes below the passband and maintaining low insertion loss.
Implementation Method 1
The first resonator includes a first piezoelectric layer and a first electrode in contact with the first piezoelectric layer. The second resonator includes a second piezoelectric layer and a second electrode in contact with the second piezoelectric layer.
Implementation Method 2
The one or more intervening layers are between the first resonator and the second resonator and acoustically couple the first resonator and the second resonator.
Implementation Method 3
The first border ring is on the first electrode. The second border ring is on the second electrode. By providing both the first border ring and the second border ring, spurious modes in the coupled resonator filter may be suppressed.
Data Source
AI summary
A coupled resonator filter includes a first resonator, a second resonator, one or more intervening layers, a first border ring, and a second border ring. The first resonator includes a first piezoelectric layer and a first electrode in contact with the first piezoelectric layer. The second resonator includes a second piezoelectric layer and a second electrode in contact with the second piezoelectric layer. The one or more intervening layers are between the first resonator and the second resonator and acoustically couple the first resonator and the second resonator. The first border ring is on the first electrode. The second border ring is on the second electrode. By providing both the first border ring and the second border ring, spurious modes in the coupled resonator filter may be suppressed, thereby improving the performance thereof.