Modelling and simulation of high-frequency (100 MHz) ultrasonic linear arrays based on single crystal LiNbO3 |
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Authors: | JY Zhang WJ XuJ Carlier XM Ji B NongaillardS Queste YP Huang |
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Institution: | a ASIC and System State Key Lab, Department of Microelectronics, Fudan University, Shanghai 200433, PR China b Département Opto-Acousto-Electronique, IEMN, UMR CNRS 8520, Université de Valenciennes, Mont Houy BP311, 59313 Valenciennes, France c Institut FEMTO-ST, CNRS UMR 6174, Université de Franche-Comté, 25044 Besançon, France |
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Abstract: | BackgroundHigh-frequency ultrasonic transducer arrays are essential for high resolution imaging in clinical analysis and Non-Destructive Evaluation (NDE). However, the fabrication of conventional backing-layer structure, which requires a pitch (distance between the centers of two adjacent elements) of half wavelength in medium, is really a great challenge.Objective and methodHere we present an alternative buffer-layer structure with a silicon lens for volumetric imaging. The requirement for the size of the pitch is less critical for this structure, making it possible to fabricate high-frequency (100 MHz) ultrasonic linear array transducers. Using silicon substrate also makes it possible to integrate the arrays with IC (Integrated Circuit). To compare with the conventional backing-layer structure, a finite element tool, COMSOL, is employed to investigate the performances of acoustic beam focusing, the influence of pitch size for the buffer-layer configuration, and to calculate the electrical properties of the arrays, including crosstalk effect and electrical impedance.ResultsFor a 100 MHz 10-element array of buffer-layer structure, the ultrasound beam in azimuth plane in water could be electronically focused to obtain a spatial resolution (a half-amplitude width) of 86 μm at the focal depth. When decreasing from half wavelength in silicon (42 μm) to half wavelength in water (7.5 μm), the pitch sizes weakly affect the focal resolution. The lateral spatial resolution is increased by 4.65% when the pitch size decreases from 42 μm to 7.5 μm. The crosstalk between adjacent elements at the central frequency is, respectively, −95 dB, −39.4 dB, and −60.5 dB for the 10-element buffer, 49-element buffer and 49-element backing arrays. Additionally, the electrical impedance magnitudes for each structure are, respectively, 4 kΩ, 26.4 kΩ, and 24.2 kΩ, which is consistent with calculation results using Krimholtz, Leedom, and Matthaei (KLM) model.ConclusionThese results show that the buffer-layer configuration is a promising alternative for the fabrication of high-frequency ultrasonic linear arrays dedicated to volumetric imaging. |
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Keywords: | High-frequency Ultrasonic array transducer Finite element calculation LiNbO3 single crystal |
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