Shielded Elastic Wave Filter Layout for Better Out-of-Band Attenuation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing elastic wave filters and duplexers suffer from insufficient out-of-band attenuation and deteriorated isolation characteristics due to direct wave propagation, which affects their performance in mobile communication devices.
Innovation Solution
The design incorporates a piezoelectric substrate with an interdigital transducer electrode, a shield electrode, and insulating films to create an electromagnetic shield effect, preventing direct wave propagation to the output terminal and enhancing out-of-band attenuation, while also improving bonding strengths with a mounting substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If signal terminals are provided on the piezoelectric substrate without shield electrodes, then the device structure is simple and easy to manufacture, but direct waves propagate to the output terminal causing insufficient out-of-band attenuation
Solution Approach 1:
A shield electrode is introduced as an intermediary element between the signal terminals on the piezoelectric substrate. The shield electrode, connected to ground potential, acts as a mediator to block direct wave propagation paths while maintaining the overall structure's manufacturability through standard electrode deposition processes
Solution Approach 2:
The electrode structure is segmented into functional zones: signal terminals for electrical connection, shield electrodes for wave blocking, and ground terminals for potential reference. This segmentation allows each component to perform its specific function while contributing to the overall out-of-band attenuation performance
2Manufacturing precision
If shield electrodes are added to block direct waves, then out-of-band attenuation is improved, but the device structure becomes more complex
Solution Approach 1:
The shield electrode structure is merged with the existing electrode layout by utilizing the same piezoelectric substrate and insulating film layers. The shield electrodes are positioned to overlap with signal terminals when viewed from above, allowing dual functionality within a unified structural framework that minimizes additional complexity
Solution Approach 2:
The shield electrodes serve multiple functions: they block direct wave propagation to improve out-of-band attenuation, provide electromagnetic shielding, and establish ground reference paths. This multi-functionality reduces the need for separate components, thereby limiting the increase in overall device complexity
3Manufacturing precision
If the first signal terminal is included in the first shield electrode when seen from above, then direct wave propagation is blocked and out-of-band attenuation increases, but the electrode layout becomes more complex
Solution Approach 1:
The shielding effectiveness is achieved by transitioning from a two-dimensional planar electrode layout to a three-dimensional stacked configuration. The first signal terminal is positioned on the insulating film above the piezoelectric substrate, while the first shield electrode is placed on the piezoelectric substrate below, creating vertical separation that blocks direct wave paths without requiring complex lateral electrode patterns
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 configuration significantly increases out-of-band attenuation and improves isolation characteristics in elastic wave filters and duplexers, enhancing their performance in mobile communication devices.
Implementation Method 1
a first shield electrode provided on the piezoelectric substrate... the first shield electrode is not electrically connected to the IDT electrode and the first and second signal terminals... direct waves of a signal are able to propagate to the first ground terminal. Therefore, the direct waves of the signal are more difficult to propagate to the output terminal
Implementation Method 2
an elastic wave filter includes a piezoelectric substrate, an interdigital transducer (IDT) electrode provided on the piezoelectric substrate
Data Source
AI summary
An elastic wave filter includes a piezoelectric substrate, an IDT electrode provided on the piezoelectric substrate, a first shield electrode provided on the piezoelectric substrate, a first insulating film laminated on the piezoelectric substrate and extending onto the first shield electrode, a first signal terminal provided on the first insulating film, a second signal terminal provided on the piezoelectric substrate, and a first ground terminal provided on the piezoelectric substrate and connected to a ground potential. The first shield electrode is not electrically connected to the IDT electrode and the first and second signal terminals. The first signal terminal is included in the first shield electrode when seen from above. One of the first signal terminal and the second signal terminal is an output terminal and the other thereof is an input terminal.