Surface Acoustic Wave Sensor Layout for Bulk Wave Isolation
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Solution Overview
Problem
Surface acoustic wave sensors face challenges in accurately determining physical characteristics of objects due to signal interference from both surface acoustic waves and bulk waves, leading to inaccurate measurements.
Innovation Solution
An object characteristics measurement apparatus is designed with a surface acoustic wave device featuring an interdigitated electrode on a piezoelectric substrate, a reflector with specific geometric configurations, and a bulk wave propagator, which separates surface acoustic waves from bulk waves based on their propagation paths and reflection times, allowing for precise extraction and analysis of surface acoustic wave signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a single transmitting-and-receiving electrode is used to downsize the surface acoustic wave device, then the device size is reduced, but bulk waves interfere with surface acoustic wave measurements
Solution Approach 1:
The device is segmented into distinct functional regions: a reaction field region for surface acoustic wave measurement and a bulk wave propagator region for bulk wave isolation. This spatial segmentation allows the device to maintain compact size while preventing bulk wave interference with surface acoustic wave measurements.
Solution Approach 2:
The bulk wave propagator is extracted as a separate functional component from the reaction field. By providing a dedicated propagation path for bulk waves that is acoustically isolated from the surface acoustic wave measurement region, bulk wave interference is eliminated while maintaining device compactness.
2Device complexity
If both surface acoustic waves and bulk waves are reflected and input to the electrode, then the device structure is simplified, but signal separation becomes difficult
Solution Approach 1:
The bulk wave propagator acts as an intermediary structure that receives bulk waves from the reaction field and guides them to a separate reflection point. This intermediary path ensures that bulk waves do not directly interfere with surface acoustic wave signals, enabling clear signal separation while maintaining relatively simple device structure.
3Volume of moving object
If the reflector is positioned close to the interdigitated electrode to reduce device size, then the device is compact, but bulk wave reflection interferes with surface acoustic wave detection
Solution Approach 1:
The bulk wave propagator extends in the depth direction (third dimension) of the piezoelectric substrate, creating a separate acoustic path for bulk waves. This dimensional separation allows the reflector to be positioned close to the electrode for compactness while bulk waves travel through a different spatial dimension, avoiding interference with surface acoustic wave detection.
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 approach enables accurate determination of physical characteristics by isolating surface acoustic wave signals from bulk wave interference, resulting in high-precision measurements of objects with a downsized and cost-effective surface acoustic wave device.
Implementation Method 1
a transmitting electrode and a receiving electrode which are constituted by comb-shaped electrode fingers provided on the piezoelectric substrate... when an electrical signal is provided to the transmitting electrode, an electric field is generated between the electrode fingers, a surface acoustic wave is excited due to a piezoelectric effect
Implementation Method 2
the surface acoustic wave propagating along the reaction field from the interdigitated electrode, the surface acoustic wave being reflected by the fourth surface of the reflector
Implementation Method 3
the bulk wave being reflected by the second surface of the piezoelectric substrate, the bulk wave propagating through an inside of the piezoelectric substrate
Data Source
AI summary
An object characteristics measurement apparatus of the invention includes a surface acoustic wave device. The surface acoustic wave device includes: an interdigitated electrode that is formed on a first surface on a piezoelectric substrate, excites an elastic wave, and receives reflection based on the elastic wave; a reflector that has a third surface and a fourth surface between the interdigitated electrode and a second surface orthogonal to the first surface in a propagation direction of the elastic wave; a reaction field that is formed between the interdigitated electrode and the reflector, in which the measured object is to be loaded; and a propagator that is formed between the reflector and the second surface.