Acoustic Wave Filter Layout for Low-Loss Sharp High-Side Selectivity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing acoustic wave filter devices face challenges in achieving low loss within the pass band and improving sharpness on the high-frequency side due to limitations in resonator Q values, which restricts their ability to handle multi-band operations effectively.
Innovation Solution
The acoustic wave filter device incorporates a series-arm resonant circuit and parallel-arm resonators with IDT electrodes having specific duty ratios and aspect ratios, where the second parallel-arm resonator has a higher duty ratio and lower aspect ratio than the first, to enhance Q values at resonant and anti-resonant frequencies, thereby reducing loss and improving high-frequency side sharpness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional resonators with uniform duty ratios are used, then the device structure is simple, but the Q values at resonant and anti-resonant frequencies are limited, resulting in high loss and poor sharpness on the high-frequency side
Solution Approach 1:
The patent applies local quality by assigning different duty ratios to different resonators within the filter circuit. Specifically, the first parallel-arm resonator has a first duty ratio while the second parallel-arm resonator has a second duty ratio that is higher than the first. This local differentiation optimizes the Q values at specific frequencies (resonant and anti-resonant) to reduce energy loss within the pass band, while maintaining overall structural simplicity through the use of standard IDT electrode configurations.
2Manufacturing precision
If conventional resonators with uniform aspect ratios are used, then the manufacturing process is simple, but the sharpness on the high-frequency side of the pass band is insufficient
Solution Approach 1:
The patent implements local quality by varying the aspect ratios of different resonators to optimize the sharpness of pass band edges. The first parallel-arm resonator has a first aspect ratio while the second parallel-arm resonator has a second aspect ratio that is lower than the first. This local optimization enhances the steepness of attenuation slopes on the high-frequency side, improving manufacturing precision for frequency-selective applications while maintaining relatively simple rectangular IDT electrode geometries.
3Reliability
If resonators with higher Q values are used, then low loss and improved sharpness are achieved, but the device complexity increases due to varied duty ratios and aspect ratios
Solution Approach 1:
The patent applies parameter changes by systematically varying the duty ratios and aspect ratios of parallel-arm resonators to achieve higher Q values. The first parallel-arm resonator has a first duty ratio and first aspect ratio, while the second parallel-arm resonator has a second duty ratio (higher than first) and second aspect ratio (lower than first). These controlled parameter variations improve selectivity and anti-interference capability for multi-band operations, while the variations remain within manufacturable ranges to limit complexity increases.
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 achieves low loss within the pass band and improved sharpness on the high-frequency side, enabling better selectivity and reduced interference with adjacent bands, suitable for multi-band operations.
Implementation Method 1
an acoustic wave resonator including an IDT electrode
Data Source
AI summary
A filter includes a series-arm resonator connected on a path connecting input/output terminals, and first and second parallel-arm resonators connected between the same node on the path and ground. A resonant frequency of the second parallel-arm resonator is higher than a resonant frequency of the first parallel-arm resonator, and an anti-resonant frequency of the second parallel-arm resonator is higher than an anti-resonant frequency of the first parallel-arm resonator. Each of the first and second parallel-arm resonators includes an acoustic wave resonator including an IDT electrode. The IDT electrode in the second parallel-arm resonator has a higher duty ratio than the IDT electrode in the first parallel-arm resonator, where the duty ratio is the ratio of the width to the pitch of electrode fingers.