SAW Resonator IDT Segmentation for Smaller Resonance-Antiresonance Gap
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional acoustic wave resonators have a constant electrode finger pitch, which limits the flexibility in adjusting the resonance and antiresonance frequencies, making it difficult to minimize the difference between these frequencies (Δf), thereby affecting the steepness of the attenuation characteristic at the passband boundary.
Innovation Solution
The acoustic wave resonator is designed with multiple areas on the IDT electrode having different electrode finger pitches, including the lowest, highest, and second-highest resonance frequencies, with the second-highest frequency being lower than the intermediate value between the lowest and highest, allowing for a smaller Δf without additional capacitive elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a constant electrode finger pitch is used in the IDT electrode, then the structure is simple and easy to manufacture, but the difference between resonance frequency and antiresonance frequency (Δf) cannot be sufficiently reduced, resulting in poor attenuation characteristic steepness
Solution Approach 1:
The IDT electrode is divided into multiple areas (first area, second area, third area) with different electrode finger pitches. Each area has a constant pitch within itself, but the pitches differ between areas. This segmentation allows independent optimization of different frequency characteristics while maintaining manufacturing simplicity.
Solution Approach 2:
Different areas of the IDT electrode are assigned different electrode finger pitches tailored to specific frequency requirements. The first area has pitch for lowest resonance frequency, the second area has pitch for highest resonance frequency, and the third area has pitch for second-highest resonance frequency. This local differentiation enables precise control of Δf without complicating the overall structure.
2Manufacturing precision
If a capacity element is connected in parallel with the IDT electrode to reduce Δf, then the antiresonance frequency decreases and Δf becomes smaller, but the device complexity increases
Solution Approach 1:
The patent extracts the frequency control function from external capacitive elements and integrates it directly into the IDT electrode structure through multiple areas with different pitches. This eliminates the need for additional parallel capacity elements while achieving the same Δf reduction effect.
Solution Approach 2:
The frequency control function that previously required separate capacitive elements is merged into the IDT electrode itself. The multiple areas with different pitches combine to provide both the resonant and anti-resonant frequency control within a single integrated structure.
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 design achieves a smaller Δf, improving the resonance characteristic and allowing for a more efficient acoustic wave filter with reduced size and improved temperature stability, while maintaining good resonance performance across a broad frequency range.
Implementation Method 1
an acoustic wave resonator having a piezoelectric substrate and an IDT (InterDigital Transducer) electrode provided on a major surface of the piezoelectric substrate
Implementation Method 2
an acoustic wave resonator having a piezoelectric substrate and an IDT (InterDigital Transducer) electrode provided on a major surface of the piezoelectric substrate
Implementation Method 3
The pair of reflectors are located on the two sides of the pluralities of electrode fingers on the piezoelectric substrate in the direction of propagation
Data Source
AI summary
An SAW resonator includes a piezoelectric substrate, an IDT electrode, and a pair of reflectors. The IDT electrode includes pluralities of electrode fingers which are aligned on the piezoelectric substrate in a direction of propagation of a SAW. The pair of reflectors are located on the two sides of the pluralities of electrode fingers on the piezoelectric substrate in the direction of propagation. The IDT electrode includes a plurality of areas which includes pluralities of electrode fingers distributed to them and have different resonance frequencies from each other. The plurality of areas include at least three areas. The second highest resonance frequency among all areas is lower than an intermediate value between the lowest resonance frequency among all areas and the highest resonance frequency among all areas.