Composite Filter Resonator Layout With Overlap Capacitive Coupling
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Solution Overview
Problem
Existing composite filter devices face challenges in achieving steep attenuation slopes without compromising the flexibility in the layout of resonators, particularly due to the need for capacitive elements connected in parallel to resonators, which restricts design freedom.
Innovation Solution
The composite filter device incorporates a first and second filter, each comprising series-arm and parallel-arm resonators, with a specific arrangement where the second resonator overlaps with a wiring electrode, providing capacitive coupling without dedicated wiring, thus enhancing attenuation steepness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If capacitive elements are connected in parallel to resonators to increase attenuation steepness, then the attenuation slope becomes steeper, but the degree of flexibility in the layout of resonators is reduced
Solution Approach 1:
The wiring electrode that originally served only for electrical connection is given an additional function by positioning it to overlap with the second acoustic wave resonator, thereby providing capacitive coupling. This multi-functionality eliminates the need for separate capacitive elements while achieving steep attenuation slopes.
Solution Approach 2:
The invention merges the wiring electrode and the capacitive element into a single structure. The wiring electrode is positioned to overlap with the second acoustic wave resonator, combining the electrical connection function and the capacitive coupling function into one component, thus maintaining layout flexibility while achieving steep attenuation.
2Manufacturing precision
If capacitive elements are added to increase attenuation steepness, then the filter characteristics are improved, but the device complexity increases
Solution Approach 1:
The wiring electrode is designed to serve dual purposes: electrical connection and capacitive coupling. By positioning it to overlap with the second acoustic wave resonator, it performs both functions simultaneously, eliminating the need for additional capacitive elements and reducing device complexity.
Solution Approach 2:
The wiring electrode serves itself by being positioned to overlap with the resonator, thereby providing the capacitive coupling function that would otherwise require a separate component. This self-service approach reduces the number of parts needed in the device.
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 increases the steepness of attenuation slopes without reducing the flexibility in resonator layout, ensuring effective signal rejection near the passband boundaries.
Implementation Method 1
The second acoustic wave resonator and the wiring electrode overlap each other when viewed in plan
Implementation Method 2
The piezoelectric substrates are each provided with an interdigital transducer (IDT)
Data Source
AI summary
In a composite filter device, a first acoustic wave resonator includes a functional electrode on a first main surface of a first piezoelectric substrate, and a wiring electrode is on the first main surface and is not connected to a signal potential. A support is on the first main surface and surrounds the first acoustic wave resonator. A second piezoelectric substrate is on the support and includes a third main surface closer to the support than a fourth main surface. A second acoustic wave resonator includes a functional electrode on the third main surface. The second acoustic wave resonator is a parallel-arm resonator higher in resonant frequency than any other parallel-arm resonator or a series-arm resonator lower in resonant frequency than any other series-arm resonator. The second acoustic wave resonator and the wiring electrode overlap each other when viewed in plan.