Acoustic Wave Multiplexer Resonator Layout for Stable Passband Attenuation
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Solution Overview
Problem
Acoustic wave filter devices in multiband systems face challenges in maintaining consistent attenuation characteristics on the lower-frequency side of the pass band, leading to variations in performance.
Innovation Solution
The design incorporates a series of acoustic wave resonators with specific electrode configurations on a piezoelectric substrate, including comb-shaped electrodes and reflective fingers, where the reflector wavelength is twice the pitch of the reflective electrode fingers, and the IDT-reflector gap is about 0.5 times the reflector wavelength, to stabilize the attenuation characteristic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a reflector wavelength longer than the IDT wavelength is used to shift unwanted higher-frequency responses, then the higher-frequency isolation is improved, but the attenuation characteristic on the lower-frequency side varies largely
Solution Approach 1:
The patent applies parameter changes by precisely controlling the IDT-reflector gap distance and the ratio between reflector wavelength and IDT wavelength. By setting the IDT-reflector gap to approximately 0.5 times the IDT wavelength and the reflector wavelength to 1.5-2.5 times the IDT wavelength, the patent achieves both suppression of higher-frequency unwanted responses and stable attenuation characteristics on the lower-frequency side through optimized geometric parameters.
Solution Approach 2:
The patent applies local quality by creating different structural configurations for series arm resonators and parallel arm resonators. Series arm resonators use reflectors with wavelengths longer than IDT wavelengths to suppress higher-frequency responses, while parallel arm resonators use reflectors with wavelengths closer to IDT wavelengths to maintain stable lower-frequency attenuation, allowing each component to have optimized local characteristics.
2Productivity
If multiple filter devices are disposed in the front end circuit to support multiband systems, then the data transmission speed is improved, but the mounting space is limited and isolation between devices is reduced
Solution Approach 1:
The patent applies merging by integrating multiple resonator functions into a single filter device structure. By combining series arm resonators and parallel arm resonators with specifically designed reflector configurations, the patent achieves multiband filtering capabilities within one compact device, eliminating the need for multiple separate filter devices and thereby reducing mounting space while maintaining high data transmission performance.
Solution Approach 2:
The patent applies universality by designing acoustic wave resonators that can handle multiple frequency bands through configurable reflector structures. The resonators are designed with adjustable parameters (electrode finger pitches, gap distances, reflector wavelengths) that enable a single device to perform multiple filtering functions across different frequency bands, making the device universally applicable to multiband communication systems.
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 prevents large variations in attenuation on the lower-frequency side of the pass band, ensuring consistent performance and reducing unwanted responses on both the lower and higher-frequency sides.
Implementation Method 1
Each of the plurality of parallel arm resonators is provided on a piezoelectric substrate
Implementation Method 2
an IDT electrode including a pair of comb-shaped electrodes facing each other
Implementation Method 3
a reflector adjacent to the IDT electrode in an acoustic wave propagation direction
Data Source
AI summary
An acoustic wave filter device includes series arm resonators and parallel arm resonators. A parallel arm resonator that has the highest resonant frequency has a reflector wavelength that is the same or substantially the same as an IDT wavelength and has an IDT-reflector gap that is about 0.5 times the reflector wavelength. The remaining parallel arm resonators each have a reflector wavelength longer than the IDT wavelength and have an IDT-reflector gap shorter than about 0.5 times the reflector wavelength.