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SH型声表面波在栅阵中传播特性的变分原理研究 总被引:1,自引:1,他引:1
提出了一个研究SH型声表面波在金属短路栅中传播时频散特性的理论方法,即根据陈东培和H.A.Haus理论,利用压电晶体中的变分原理和SH型表面波COM模型分析了栅阵中SH型声表面波的传播特性。该方法的最大优点是不需要使用复杂的Green’s function,其理论分析结果与Hashimoto有限元程序运算结果相一致。Hashimoto的程序在计算ST-90°X石英等一些晶体切向上短路栅的频散关系时是无解的。而这个新方法能很好的计算这些晶体上短路栅的频散关系。 相似文献
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声表面波耦合模模型参量的快速计算 总被引:1,自引:0,他引:1
根据分层介质理论精确求解压电基片和金属膜中的声波,计算了声表面波传播速度、机电耦合系数、静电容。结合陈-Haus理论,分析了短路栅阵的声表面波的传播特性,得到新的单电极栅阵栅条反射系数计算公式。计算了X-112°Y LiTaO_3上镀铝和ST石英上镀金两种情况下的耦合模模型参量,理论计算结果和国际上通用的Hashimoto程序计算结果吻合较好。实验测定了ST石英上镀金的反射系数,测试结果和理论结果更加符合。 相似文献
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基于有限元理论,给出了基于ANSYS提取单相单向换能器(Single Phase Unidirectional Transducers,SPUDT)耦合模参数的方法。首先,结合声表面波在压电介质中的传播原理,给出了压电有限元分析方程和对应的ANSYS分析步骤。然后针对SPUDT结构,给出了周期性近似分析的理论模型,利用耦合场分析对其进行模态分析和谐响应分析,最后结合两者的结果来计算SPUDT的耦合模参数。本文给出基底材料为压电晶体128°YX-LiNbO3和YZ-LiNbO3,电极材料为铝的三种不同SPUDT的计算结果,理论结果与Hashimoto和Hartmann文献报道的结果相吻合,并且和实验测试的结果基本一致。从而给出了提取SPUDT耦合模参数的一种通用、有效的方法。 相似文献
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利用声表面波(SAW)磁致伸缩效应可以实现一种快速、高灵敏度的电流检测方法,但磁致伸缩薄膜内部矫顽力导致了明显的磁滞误差。磁致伸缩薄膜的栅阵化设计可以减小磁致伸缩时薄膜内部矫顽力,抑制磁滞现象,从而实现高灵敏和低迟滞误差的SAW电流检测。结合有限元和耦合模理论对沉积铁钴(FeCo)薄膜栅阵的声表面波电流传感器中的磁致伸缩效应进行分析,对传感响应进行仿真,确定优化的传感结构参数。为验证理论分析,实验研制了频率为150 MHz的声表面波电流传感器件,并结合差分振荡电路及亥姆霍兹线圈,建立传感器测试系统.实验结果表明,磁致伸缩薄膜的栅阵设计大幅降低了迟滞误差,并显著提升了传感器灵敏度。 相似文献
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本文给出一个变分表达式,它适用于自由表面和金属化表面上声表面波传播与散射分析。然后应用此表达式导出压电晶体材料声表面波机电耦合系数K~2作为材料常数函数的近似解析表达式。并进一步求解了短路金属栅阵在同步频率附近的波表面反射系数,给出其作为基底与金属膜材料常数和金属条几何参数函数的解析表达。结果特别指出了导致上述效应的各种物理机制间的相互关系。数值结果与实验结果相符,变分处理简化了数学过程而突出了其中物理规律。 相似文献
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研究了谐振器指条厚度对质量型声表面波传感器灵敏度的影响.利用耦合模方程推导出耦合模参量与周期栅阵禁带边界频率的关系,结合有限元及P矩阵模型,获得了声表面波传感器灵敏度随指条厚度的变化关系。制备3种不同铝指条厚度(1600?,1900?,3100?)的声表面波谐振器,通过对其表面中心区域沉积SiO_2层验证了计算结果。结果表明:采用ST-X石英基底的声表面波谐振器对SiO_2负载检测时,传感器的灵敏度随铝指条厚度的增加先变大后减小,最优归一化指条厚度为1.9%。分析表明,指条厚度对传感器灵敏度的影响主要来自于传播速度和耦合系数的共同作用,通过优化指条厚度的方法可改善传感器的灵敏度. 相似文献
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Based on D.P. Chen and Haus' theory, a theoretical method was presented to analyze dispersion characteristics of SH-type surface acoustic waves (SAWs) propagating on periodic metallic grating structures with a variational principle and coupling-of-modes equation. Without using complicated Green's function, the calculating results of the method agree well with those of Hashimoto's theory. On the other hand, Hashimoto's method is helpless for calculating the dispersion relation of short-circuited gratings on ST-90°X quartz etc. However, the method developed in this paper can successfully calculate it. 相似文献
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The effect of a metal layer over an elastic substrate on surface acoustic wave propagating in the structure can be evaluated precisely for semi-infinite solids and infinite plates, but there is no accurate analytical solution if the finite size of the plate has to be considered. By expanding displacements with eigensolutions of surface acoustic waves in a semi-inifite solid, a set of two-dimensional equations similar to the Mindlin plate theory are obtained. Then for a thin electrode layer, the effect is considered through the approximation of displacements in the metal layer with the ones in the substrate, and an integration over the thickness incorporated the properties of the metal layer into equations through the modification of material properties with the decaying indices of surface acoustic waves and the thickness of the metal layer. Using AT-cut quartz crystal as the substrate, we present the effect of silver electrode layers of finite thickness on the phase velocity of propagating surface acoustic waves. 相似文献
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In this review, we present our recent work on making structured metals transparent for broadband electromagnetic waves and acoustic waves via excitation of surface waves. First, we theoretically show that one-dimensional metallic gratings can become transparent and completely antireflective for extremely broadband electromagnetic waves by relying on surface plasmons or spoof surface plasmons. Second, we experimentally demonstrate that metallic gratings with narrow slits are highly transparent for broadband terahertz waves at oblique incidence and high transmission efficiency is insensitive to the metal thickness. Further, we significantly develop oblique metal gratings transparent for broadband electromagnetic waves (including optical waves and terahertz ones) under normal incidence. In the third, we find the principles of broadband transparency for structured metals can be extended from one-dimensional metallic gratings to two-dimensional cases. Moreover, similar phenomena are found in sonic artificially metallic structures, which present the transparency for broadband acoustic waves. These investigations provide guidelines to develop many novel materials and devices, such as transparent conducting panels, antireflective solar cells, and other broadband metamaterials and stealth technologies. 相似文献
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Efficient outcoupling of surface-plasma waves to radiation modes by use of dielectric diffraction gratings on a flat metallic surface is discussed. The dielectric gratings, which have a surface-relief structure with only several tens of nanometers in peak-to-trough height on a flat metal surface, can efficiently extract radiation modes propagating in free space from the surface-plasmon modes. An outcoupling efficiency of 50% is estimated with the rigorous coupled-wave diffraction theory, and it is confirmed by the experiment. 相似文献
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Jijun Wang Zhonghua Shen Xiaowu Ni Baiqiang Xu Jianfei Guan Jian Lu 《Optics & Laser Technology》2007,39(1):21-28
The optimum finite element model in the system consisting of a transparent coating and an opaque substrate is established based on the analysis of two important parameters: meshing size and time step, and the stability of solution. Taking into account the temperature dependence of material properties, the transient temperature and temperature gradient field are obtained. According to the thermoelastic theory, this temperature gradient field can be taken as a buried bulk source to generate ultrasonic wave. The surface acoustic waves (SAWs) are obtained. The influence of the coating thickness on the SAWs is analyzed. The model provides a useful tool for the determination of modes which are generated by a laser source in transparent coating on opaque substrate. The surface skimming longitudinal wave exists for the multiple oscillations and it charges from unipolar waveforms to dipolar. 相似文献
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Reflection of zero-order normal acoustic waves excited in a thin piezoelectric plate from a set of conducting strips of a finite thickness is studied both theoretically and experimentally. The analysis shows that the effects produced by the short-circuiting of the plate surface and by the elastic load on the impedance ratio of adjacent plate segments are in opposition to each other. These effects can be commensurable, and, hence, for each wave type, there is a certain value of the strip thickness at which the reflection coefficient becomes equal to zero. The experimental results obtained for a shear horizontal normal wave (an SH 0 wave) propagating in a lithium niobate plate are in good agreement with the theory and justify the use of the equivalent-circuit model in analyzing the properties of reflectors of the type under study. 相似文献
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本文利用严格数值仿真研究了550~700 nm波段的可见光通过金属光栅耦合方式激发的表面等离激元(SPP)波在金属表面的光栅衍射行为与现象。研究结果表明:SPP波在金属表面的衍射行为与自由空间光相比有极大不同,由于SPP波的近场属性,经金属光栅衍射后在近场可表现出明显的光栅分光现象,但经过一段传输距离后则分光现象消失而表现为不同级次的光合为同一束光;在近场衍射情况下,其情况与自由空间光衍射行为类似,对SPP亚波长金属光栅来说同样只有零级透射光;而当金属光栅周期大于SPP波长时,高级衍射级次则开始出现。研究结果对下一步在金属表面上实现微米级片光谱仪器具有重要借鉴意义。 相似文献
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Considering a piezo-plasma-like layer with finite thickness and hexagonal symmetry whose main symmetry axis is parallel to the z axis and approximating it by an isotropic medium, we study the coupling of the elastic wave with plasma properties of the medium with and without spatial dispersion and collisions. In this case we investigate the coupled surface quasi elasto-electromagnetic wave propagating on the interface of piezoelectric layer with vacuum. Furthermore, the coupling of elasticity and ion-acoustic waves is investigated. 相似文献
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D. Cerniglia A. Pantano C. Mineo 《Applied Physics A: Materials Science & Processing》2011,105(4):959-967
The different ultrasonic fields generated in metallic materials by a laser beam with flat and Gaussian profile are investigated
experimentally and using the finite element method (FEM). A high power laser beam irradiating a solid surface produces elastic
waves with a mechanics that depends on many parameters, including the profile of the laser beam. The influence of the beam
profile is investigated with the FEM analysis, considering the temperature dependence of material properties. 相似文献