共查询到19条相似文献,搜索用时 296 毫秒
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与IC标签相比,声表面波标签有其独特的优势.在仿真研究的基础上,对声表面波标签进行了设计、制作和测试.标签设计主要体现在压电基片材料选择、叉指换能器设计、反射栅设计3个方面;实际制作了6组结构各不相同的标签并进行了封装;通过网络分析仪对设计制作的标签进行了测试,包括特征频率测试、反射栅编码测试、叉指换能器激发效率测试3个部分.测试结果表明,标签特征频率与设计要求一致;通过对回波脉冲幅值的判别可实现对标签编码的识别;叉指换能器对数增多和孔径增大都会增加其激发效率. 相似文献
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FBG反射谱展宽效应在轨道传感器中的应用研究 总被引:1,自引:0,他引:1
实验验证了光纤Bragg光栅(FBG)在非均匀应力下的反射谱展宽效应,并将这种展宽效应应用于轨道列车轮重、位置和轴数的监测。将FBG传感器置于铁轨特定位置,当受非均匀应力时,列车轮重的增加会引起FBG反射谱展宽,反映为检测光强增大。利用模型验证了FBG反射谱分别在温度、均匀应力及非均匀应力下的变化,根据有限元分析模拟铁轨模型的应变分布,进而通过模型实验和实际测试验证了这种方案的可行性。 相似文献
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在简述反射栅扩散体工作的基本理论依据后,重点对相位反射栅扩散体的声扩散特性、设计参数进行了分析说明,最后简要介绍了幅度反射栅扩散体。 相似文献
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本文研究电磁波在一类特殊非均匀媒质中的反射问题,首先,根据矩阵分析理论导出了反射系数具有解析形式的一类特殊非均匀媒质剖面--负二次剖面,进行获得了反射系数的具体表达式,它由简单的初等函数给出,最后文中验证了本文公式的正确性。 相似文献
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无源UHF RFID标签的低成本阻抗匹配网络设计 总被引:1,自引:0,他引:1
提出了一种符合ISO/IEC18000-6C标准的无源RFID(射频识别)标签的低成本阻抗匹配网络。该设计基于复功率波反射系数的概念,修正芯片输入阻抗,在片内添加阻抗匹配电路。通过变化芯片阻抗和天线共轭匹配及失配间切换,有效完成信号的调制反射。提出的电路结构简单,易于实现,在读写器、标签天线和芯片之间实现了功率传输的最大化,提高了芯片输入电压以及读写器对标签反射信号的识别率。采用该阻抗匹配网络的芯片基于chartered 0.35μm CMOS工艺实现。测试结果表明,在923MHz频带下,倍压电路输出可达1.47V,标签满足系统设计要求。 相似文献
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Time Domain Analysis of SAW Reflectors 总被引:1,自引:0,他引:1
《Microwave Theory and Techniques》1979,27(2):194-198
A time domain analysis of high-reflectivity SAW reflector arrays is shown to yield values of stripe reflectivity, center frequency, and effective reflections plane penetration. An examination of the approach shows that the results are insensitive to device losses, RF coupling, and transducer response. Experimental results confirm the validity of the technique. 相似文献
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Blood flow can be described by a scattering function, i.e., by the expected distribution of Doppler shifts and delays that are introduced by a collection of moving point scatterers. An equivalent representation is the echo autocovariance function, measured for a sequence of echoes from different transmitted pulses. Tissue structure can be characterized by the frequency dependence of acoustic reflectivity for echoes from large acoustic discontinuities (highlight echoes), and by the "texture" of the echo from a distributed reflector. Highlight structure and frequency dependence of tissue reflectivity can be obtained from the signal-echo cross-ambiguity function, and texture differences are related to differences in echo power spectra and auto-covariance functions. 相似文献
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This paper reports a computationally efficient, grid-independent method for calculating the reflectivity of deep-etch distributed Bragg reflector (DBR) gratings. The method employs Gaussian beam propagation in conjunction with a Fabry-Perot model that includes the effects of multiple reflections in multiple cavities. We include both, grating pitch and number of Bragg pairs in our analysis. We obtain very good agreement with results generated by a Helmholtz equation solver 相似文献
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Physical optics (po) and the method of equivalent currents (mec) are used for the formulation and calculation of the backscatter cross section of both the triangular and square trihedral corner reflectors. Scattering from a trihedral corner reflector is dominated by single, double, and triple reflections by the interior walls. A physical optics integration is performed on the entire surface of each plate for the evaluation of the singly reflected fields. Doubly and triply reflected fields are evaluated by first using geometrical optics (go) at initial reflections to calculate the incident plane wave on the plate where the last reflection occurs. Physical optics is then applied on the illuminated area of that plate. First-order diffractions, which are based on the fringe current expressions for the exterior edges of the trihedral, are also included in the analysis. Predictions compare very well with both experimental and fdtd data. 相似文献
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目前城市地下电力管线错综复杂,迫切需要一种对电力管线快速标识定位的方法。该文提出了一种基于声表面波射频识别(SAW RFID)技术的定位方法,利用SAW RFID的强穿透能力,将SAW标签间隔埋入地下管线上方构造位置网格,与全球定位系统(GPS)/北斗定位技术融合形成快速定位方案;同时,为了提高地下标签的探测距离,研究设计了单相单向换能器(SPUDT),以及适合埋在地下介质中的标签天线;最后完成了实际地下土壤环境的场景测试,验证了SAW RFID地下电力管线定位方法的性能及优势。 相似文献
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为获取光学目标更多的特征信息、达到目标识别的目的,文中利用不同目标回波特征受到湍流大气调制作用的差异性,将目标回波的闪烁效应作为目标识别的手段之一。采用功率谱反演法生成随机相位屏模拟双程湍流大气扰动,利用硬边光阑展开为有限级数和的形式以及Collins衍射积分公式推导角反射器、镜头目标和朗伯漫反射体的反射光的复振幅分布,通过原路返回处的光强分布得到反射光的闪烁指数。分析了湍流强度和目标尺寸对上述三种目标回波的闪烁指数的影响,并进行了实验验证。研究结果表明:光学目标与漫反射目标回波的闪烁指数差别明显,整体相差一个数量级,随着口径的增大,光学目标回波闪烁指数整体上呈现减小的趋势;角反射器和镜头目标回波的闪烁指数在数值上差别不明显,但可以通过多组测试结果绘制回波闪烁指数随时间的变化曲线的方法将二者进行大致的区分。该方法可以快速地从漫反射背景中识别出光学目标,同时也为光学目标的分类识别提供了参考价值。 相似文献
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The reflectivity versus incident angle of a GaP/Au reflector,a GaP/SiO_2/Au triple ODR(omni-directional reflector) and a GaP/ITO/Au triple ODR was calculated.Compared to AlGaInP LEDs with a GaAs absorbing substrate, thin film LEDs with a Au reflector,a SiO_2 ODR and an ITO ODR were fabricated.At a current of 20 mA,the optical output power of four samples was respectively 1.04,1.14,2.53 and 2.15 mW.The Au diffusion in the annealing process reduces the reflectivity of the Au/GaP reflector to 9%.The differe... 相似文献
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V. F. Dmitriev A. S. Koigerov 《Journal of Communications Technology and Electronics》2011,56(10):1256-1265
A realization of the method of correlation signal processing for solving problems of collisions in radio frequency identification
(RFID) systems using RFID tags is considered. The reflecting structures of RFID tags are fabricated in the form of surface
inhomogeneities with typical dimensions of several tens of nanometers. An algorithm for the search of codes for SAW RFID tags
and a method for calculating the SAW RFID tags with phase-shift keyed codes are proposed. Modeling and experimental study
of SAW RFID tags designed for formation of signals with phase-shift keyed codes possessing specified correlation properties
are performed. Oscillograms of signals formed by the RFID tags are presented, and their correlation properties are studied. 相似文献