Acoustic Wave Filter Layout for Individual Resonator Frequency Tuning
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Solution Overview
Problem
Existing acoustic wave devices, particularly those used in ladder filters, face challenges in separately adjusting the frequency of individual resonators, limiting their flexibility and efficiency.
Innovation Solution
The proposed filter design includes a piezoelectric film with an acoustic wave resonator and a capacitor connected in parallel, featuring a functional electrode with busbars and electrodes arranged to allow easy adjustment of resonator frequencies through capacitance variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the thickness of the piezoelectric substrate is adjusted to change frequency, then the frequency of the acoustic wave resonator is adjusted, but it becomes difficult to separately adjust the frequency of individual resonators in a ladder filter
Solution Approach 1:
The invention divides the frequency adjustment function into two independent parts: (1) global frequency adjustment through piezoelectric substrate thickness, and (2) individual resonator frequency adjustment through separate capacitors connected to each resonator. This segmentation allows each resonator's frequency to be independently tuned without affecting others, resolving the contradiction between frequency adaptability and adjustment complexity.
Solution Approach 2:
The invention introduces capacitance as an additional adjustable parameter for frequency control. By connecting capacitors to individual resonators, the resonant frequency can be adjusted through capacitance value changes without requiring physical modification of the piezoelectric substrate thickness for each resonator, thereby enabling separate frequency adjustment while maintaining device simplicity.
2Adaptability or versatility
If a capacitor is added to each resonator for frequency adjustment, then individual resonator frequency can be adjusted, but the device complexity increases
Solution Approach 1:
The invention merges the capacitor with the resonator structure by connecting them in parallel at the resonator terminals. This integration allows the capacitor to become an inherent part of the resonator circuit, enabling frequency adjustment without adding separate, complex adjustment mechanisms. The merged structure achieves individual frequency control while minimizing additional 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 enables easy adjustment of the frequency of individual resonators, improving the flexibility and efficiency of the acoustic wave device, particularly in ladder filter applications.
Implementation Method 1
an acoustic wave resonator that includes a functional electrode on the piezoelectric film
Implementation Method 2
a capacitor on the piezoelectric film and connected in parallel to the acoustic wave resonator
Data Source
AI summary
A filter includes a piezoelectric film, an acoustic wave resonator including a functional electrode on the piezoelectric film, a capacitor connected in parallel to the acoustic wave resonator, and a resonator electrically connected to the acoustic wave resonator. The functional electrode includes first and second busbars facing each other and first and second electrodes respectively connected to the first and second busbars. The filter further includes a connection electrode on the piezoelectric film and electrically connecting the capacitor and the second busbar to each other. The capacitor includes the first busbar, an insulation film on the first busbar, and a capacitance electrode on the insulation film and that is electrically insulated from the first busbar.