Ultrasonic Transceiver Acoustic Matching Layer Reverberation Control
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Solution Overview
Problem
Conventional ultrasonic transceivers for gas flow measurement suffer from significant reverberation in the received ultrasonic wave, leading to inaccurate detection of the zero-crossing point and erroneous measurement of gas flow rates.
Innovation Solution
The ultrasonic transceiver incorporates a piezoelectric element with multiple acoustic matching layers, where at least a part of the joining surface between the acoustic matching layers is inside the outer periphery of the matching layer on the piezoelectric element side, effectively suppressing the propagation of indirect waves and reducing reverberation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple acoustic matching layers are stacked to improve radiation efficiency and match acoustic impedance with gas, then the ultrasonic wave can efficiently enter the gas, but reverberation in the received wave increases
Solution Approach 1:
The acoustic matching layer is divided into multiple layers with different acoustic impedances. Each layer has a specific acoustic impedance value that forms a gradient between the piezoelectric element and the gas, enabling progressive impedance matching while controlling reverberation through optimized layer thicknesses and impedance values
Solution Approach 2:
The acoustic impedance values and thicknesses of the matching layers are optimized to specific ranges. The first matching layer has acoustic impedance between 1.0×10^6 to 3.0×10^6 Rayl, the second layer has acoustic impedance between 0.3×10^6 to 1.5×10^6 Rayl, with thicknesses controlled at λ/4 or λ/8 of the ultrasonic wavelength to minimize reverberation while maintaining transmission efficiency
2Reliability
If acoustic matching layers are designed to match with gas having small acoustic impedance, then radiation efficiency is improved, but the reference point for measuring propagation time cannot be accurately detected
Solution Approach 1:
The acoustic impedance of the matching layers is optimized to specific ranges (first layer: 1.0×10^6 to 3.0×10^6 Rayl, second layer: 0.3×10^6 to 1.5×10^6 Rayl) to balance radiation efficiency with signal clarity. The thicknesses are controlled at λ/4 or λ/8 of the ultrasonic wavelength to minimize reverberation that would obscure the reference point
Solution Approach 2:
The matching layers are designed with specific thicknesses (λ/4 or λ/8) that are optimized to provide sufficient impedance matching while preventing excessive reverberation. This partial optimization approach ensures the reference point remains detectable while achieving adequate radiation efficiency
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 enables stable measurement of ultrasonic signals by minimizing reverberation, resulting in accurate detection of propagation time and improved flow rate measurement accuracy.
Implementation Method 1
an ultrasonic transceiver that transmits and receives an ultrasonic wave by using a piezoelectric element or the like
Implementation Method 2
the difference in acoustic impedance between the gas and the piezoelectric element is large, and the ultrasonic wave is therefore easily reflected at an interface between the piezoelectric element and the gas. Therefore, in the ultrasonic transceiver, an acoustic matching layer is provided at the interface between the piezoelectric element and the gas in order to enable the ultrasonic wave to efficiently enter the gas from the piezoelectric element
Data Source
Figure 1A~1B
Figure 2
Figure 3A~3B
AI summary
There are provided piezoelectric element (12), case (11) having conductivity, first acoustic matching layer (13) bonded on case (11), and second acoustic matching layer (14) stacked on and bonded to first acoustic matching layer (13). A joining part between first acoustic matching layer (13) and second acoustic matching layer (14) is located inside an outer periphery of a joining surface of first acoustic matching layer (13) that is joined to second acoustic matching layer (14). This configuration can prevent indirect wave (16) generated in first acoustic matching layer (13) from propagating to second acoustic matching layer (14), and can therefore reduce reverberation of an ultrasonic wave.