SAW Sensor Waveguide Positioning to Suppress Bulk Waves
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Solution Overview
Problem
Current sensor devices face challenges in accurately detecting changes in the state of a surface acoustic wave (SAW) propagation path due to diffusion into the substrate, leading to unnecessary bulk waves that introduce noise and reduce detection sensitivity.
Innovation Solution
The sensor device incorporates a waveguide positioned between the first and second IDT electrodes on the substrate surface, with the distance between the electrodes and the waveguide optimized to be shorter than the interval between the reference and signal electrodes, minimizing bulk wave generation and enhancing detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the distance between the IDT electrode and the waveguide is increased, then the SAW propagation path is lengthened for better detection, but bulk wave generation increases causing noise and reduced sensitivity
Solution Approach 1:
A reflector electrode is introduced as an intermediary component between the IDT electrode and the waveguide. This reflector electrode serves as a mediator that reflects bulk waves away from the waveguide, preventing them from reaching the detection region and causing noise, while allowing the SAW propagation path to be extended for improved detection sensitivity.
Solution Approach 2:
The electrode structure is segmented into multiple functional parts: the IDT electrode for generating SAWs, the reflector electrode for blocking bulk waves, and the waveguide for signal transmission. This segmentation allows each component to perform its specific function optimally, with the reflector electrode specifically tasked with eliminating bulk wave interference.
2Object-affected harmful factors
If the distance between the IDT electrode and the waveguide is decreased, then bulk wave generation is reduced, but the SAW propagation path is shortened reducing detection capability
Solution Approach 1:
The reflector electrode acts as a mediator that enables the system to overcome the limitation of short propagation paths. By placing the reflector between the IDT and waveguide, the system can extend the effective detection path while the reflector continuously manages bulk wave interference, maintaining low noise levels throughout the extended path.
3Area of stationary object
If the interval between reference and signal electrodes is decreased, then device size is reduced, but detection accuracy is compromised
Solution Approach 1:
The reflector electrode serves as a mediator that protects the compact electrode configuration from bulk wave interference. This allows the reference and signal electrodes to be positioned closer together without sacrificing detection accuracy, as the reflector blocks bulk waves that would otherwise contaminate the measurement signal in the reduced-size configuration.
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 reduces sensitivity variation and improves detection accuracy by minimizing the conversion of SAW energy into bulk waves, allowing for more precise measurement of changes in the waveguide's surface state.
Implementation Method 1
an elastic wave sensor including a sensitive film having adsorptivity to a measurement target substance on a propagation path of a surface acoustic wave
Implementation Method 2
The first IDT electrode and the second IDT electrode are positioned on the substrate surface
Implementation Method 3
The waveguide is positioned on the substrate surface and between the first IDT electrode and the second IDT electrode
Implementation Method 4
a sensitive film having adsorptivity to a measurement target substance on a propagation path of a surface acoustic wave
Data Source
AI summary
A sensor device includes a substrate having a substrate surface, a first IDT electrode, a second IDT electrode, and a waveguide. The first IDT electrode and the second IDT electrode are positioned on the substrate surface. The waveguide is positioned on the substrate surface and between the first IDT electrode and the second IDT electrode. At least one of the first IDT electrode and the second IDT electrode includes a reference electrode and a signal electrode each including a plurality of electrode fingers, the plurality of electrode fingers being arranged in a juxtaposed manner in one direction. A distance between the at least one of the first IDT electrode and the second IDT electrode and the waveguide is shorter than an interval between the reference electrode and the signal electrode in the one direction.