SAW Band-Pass Filter Layout for Easier Frequency Adjustment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Elastic wave devices with multiple surface acoustic wave elements on the same piezoelectric substrate face manufacturing variations in electrode line width and film thickness, leading to inconsistent frequency characteristics and complex frequency adjustment processes, particularly for band-pass filters.
Innovation Solution
The elastic wave device incorporates a piezoelectric substrate with first and second band-pass filters, each with IDT electrodes and dielectric films of the same or similar thickness and material, where the duty ratios of the first IDT electrodes are larger than those of the second, allowing for easier frequency adjustment by ensuring |Tx1−Rx1|/f1>|Tx2−Rx2|/f2, facilitating simultaneous frequency adjustment of both filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If separate frequency adjustment is performed for each surface acoustic wave element, then frequency characteristics can be optimized for each element, but the manufacturing process becomes complex
Solution Approach 1:
The patent applies local quality by making the first IDT electrodes have a larger duty ratio than the second IDT electrodes. This local differentiation in electrode geometry allows each band-pass filter to have distinct frequency characteristics while being fabricated using the same general process, thus optimizing frequency performance without requiring completely separate manufacturing procedures for each element.
Solution Approach 2:
The patent changes the duty ratio parameter of the IDT electrodes to control frequency characteristics. By adjusting the duty ratio (the ratio of electrode finger width to period) rather than requiring separate manufacturing processes, the invention achieves frequency optimization through a controllable geometric parameter that can be set during a unified fabrication process.
2Manufacturing precision
If manufacturing variations in line width or film thickness occur, then frequency characteristics vary between elements, but maintaining strict control increases manufacturing difficulty
Solution Approach 1:
The invention uses duty ratio as a design parameter that compensates for manufacturing variations. By carefully selecting different duty ratios for the first and second IDT electrodes, the patent ensures that even with normal manufacturing tolerances in line width and film thickness, the frequency characteristics remain within acceptable ranges without requiring ultra-precise manufacturing control.
Solution Approach 2:
The patent introduces asymmetry in the duty ratios of the IDT electrodes between the two band-pass filters. This asymmetric design makes the frequency characteristics inherently different and more robust to manufacturing variations, as the frequency difference is primarily determined by the duty ratio difference rather than by precise control of absolute dimensions that are subject to manufacturing tolerances.
3Productivity
If multiple band-pass filters are provided on the same piezoelectric substrate, then device integration is improved, but frequency adjustment becomes more complex
Solution Approach 1:
The patent applies local quality by differentiating the duty ratios of IDT electrodes for different band-pass filters on the same substrate. This allows each filter to have its own frequency characteristics through local geometric variation rather than requiring separate substrates or complex post-fabrication adjustments, thus achieving high integration while keeping frequency adjustment relatively simple.
Solution Approach 2:
The invention uses a universal fabrication process for multiple band-pass filters on the same piezoelectric substrate, with frequency differentiation achieved through geometric parameter (duty ratio) control rather than requiring separate manufacturing procedures. This multi-functional approach allows simultaneous fabrication of multiple filters with different characteristics using the same base process.
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 simplifies the frequency adjustment of band-pass filters, reduces manufacturing complexity, and improves productivity by maintaining consistent filter characteristics across different communication bands.
Implementation Method 1
an elastic wave device includes a piezoelectric substrate, a first band-pass filter including a plurality of first IDT electrodes disposed on the piezoelectric substrate
Implementation Method 2
two surface acoustic wave elements having different frequency characteristics are provided on the same piezoelectric substrate
Data Source
AI summary
An elastic wave device includes a first band-pass filter on a piezoelectric substrate and including first IDT electrodes and a first dielectric film, and a second band-pass filter on the piezoelectric substrate and including second IDT electrodes and a second dielectric film. At least one pair among a pair of the first and second IDT electrodes and a pair of the first and second dielectric films has the same or substantially the same film thickness and is made of the same material. A relationship |Tx1−Rx1|/f1>|Tx2−Rx2|/f2 is satisfied. A weighted average of duty ratios of the first IDT electrodes is larger than a weighted average of duty ratios of the second IDT electrodes.