Acoustic Wave Resonator Shielding for Filter Isolation Loss
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In laminated acoustic wave devices, the long path length from the upper filter to the ground electrode leads to electromagnetic coupling, resulting in decreased filter characteristics such as isolation characteristics between filters.
Innovation Solution
Incorporating a conductive shield layer close to the resonator to reduce the loop area of the signal path to the ground electrode, thereby minimizing electromagnetic coupling between filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the ground electrode is disposed on the mounting substrate in a laminated acoustic wave device, then the device structure is simplified and easy to manufacture, but the path length from the upper filter to the ground electrode becomes long, causing electromagnetic coupling and decreased filter characteristics
Solution Approach 1:
A ground electrode layer is introduced as an intermediary element between the upper and lower filters. This ground electrode layer is disposed on the piezoelectric substrate itself (not just on the mounting substrate), serving as a local reference potential that shields the signal paths from electromagnetic coupling with other filters, thereby maintaining filter characteristics while keeping the overall device structure simple
Solution Approach 2:
The grounding structure is extended from a single-plane configuration (only on mounting substrate) to a multi-layer configuration (on both piezoelectric substrate and mounting substrate). By adding the ground electrode layer in the vertical dimension within the device stack, the patent creates multiple reference potential planes that reduce electromagnetic coupling without increasing lateral path length
2Reliability
If the path length from the filter to the ground electrode is reduced, then electromagnetic coupling is minimized and filter characteristics are improved, but the device structure becomes more complex
Solution Approach 1:
The ground electrode layer is merged with the existing piezoelectric substrate structure rather than being added as a completely separate component. The ground electrode pattern is formed on the same substrate that carries the filter structures, combining the substrate's mechanical support function with the electrical grounding function, thereby reducing path length without proportionally increasing complexity
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 effectively reduces or prevents the decrease in filter characteristics, maintaining optimal attenuation and isolation performance even with longer path lengths.
Implementation Method 1
a conductive shield layer... to reduce the loop area of the signal path leading to the ground electrode through the first resonator... the electromagnetic coupling between the filters can be reduced or prevented
Data Source
AI summary
An acoustic wave device includes a piezoelectric substrate including an outer terminal electrode and first and second main surfaces, a filter including a resonator on the first main surface, and a conductive shield layer. The outer terminal electrode includes first and second terminals and a ground terminal. The filter is connected to the first and second terminals. The shield layer is above the resonator to overlap with at least a portion of the resonator in a case where the piezoelectric substrate is viewed in a plan view in a thickness direction of the piezoelectric substrate. The resonator includes an electrode electrically connected to the first or second terminal and an electrode connected to the ground terminal with the shield layer interposed between the electrode and the ground terminal.