共查询到19条相似文献,搜索用时 200 毫秒
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介绍了一种测量低损耗天线罩材料的开腔高温自动测量系统。该系统采用扫频方式程控标量网络分析仪对开腔进行扫频测量,得到介质加载前后腔体的谐振频率与Q值,并由此计算出被测材料的介电常数和损耗角正切;介质采用特制硅碳管加热,由温度控制器对其控制,最高温度可达1 000 ℃以上。用此系统对聚四氟乙烯和一种低损耗天线罩材料进行测量对比。结果表明,测得的聚四氟乙烯结果与文献结果相近,天线罩材料相对介电常数的实部随温度升高而增加。 相似文献
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针对NaCl水溶液(0.001–0.5 mol/L)介电特性, 实验调查了频率(200–6.25 GHz), 温度(293–353 K)、 浓度相关复介电常数. 结果表明: 频率增大的过程中虚部呈逐渐减小的趋势, 高温使离子扰动增大, 破坏了溶液内部水分子四面体结构和氢键构象而使介电常数实部减小. 与纯水相比, 溶液的损耗角正切在高温353 K低频区下降明显. 同时发现2.45和5.8 GHz的复介电常数随温度变化的温度窗效应, 温度窗效应导致微波加热时耗散功率的振荡变化, 温度分布不均匀现象在实验中得以证实.
关键词:
微波
复介电常数
介电特性
高温探头 相似文献
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Dielectric-filled waveguides may be advantageous for heating reactor-grade tokamak plasmas, due to their compactness and power-handling capability. We present a theoretical analysis of coax excitation and plasma impedance for a dielectric-filled rectangular waveguide. The plasma reflection coefficient is obtained by matching plasma and waveguide fields at the interface. The numerical results show that the reflection coefficients can be made small by careful tailoring of the waveguide dimensions to the density profile for heating at the second or third harmonic of deuterium. We present a scattering matrix approach for the design of a coaxial feed to match the waveguide in the presence of a wide range of plasma loading. For a waveguide filled with a high permittivity dielectric, a shorted probe gives better coupling than an open-ended probe. 相似文献
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Diego González-Herrero Jose María Muñoz Carlos Torres Pablo Hernández-Gómez Óscar Alejos Carlos de Francisco 《Applied Physics A: Materials Science & Processing》2013,112(3):719-725
A new method for measuring the electromagnetic properties (permittivity and permeability) of nanopowder materials in a wide microwave region is presented. Unlike previously developed systems, our experimental setup is based on reflection measurements over a short-circuited transmission line combined with the application of a uniform magnetostatic field. When this field is sufficiently high to saturate the material, the effective permeability of the sample equals the permeability of free space, without modifying its electrical properties. Hence, for each frequency, the permittivity can be obtained through the measurement of a single scattering parameter, such as the reflection coefficient. After this first measurement, and once the external field is removed, the reflection coefficient can be used again to obtain the permeability by means of the permittivity value obtained before. As the major advantage, this procedure allows the recording of the experimental data in just one sweep, using one-port measurements, and without modifying the geometrical characteristics of the sample holder. Hence, the measurement process can be easily automated. 相似文献
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V. Tamo?iūnas V. Shugurov M. Tamo?iūnien? K.-F. Berggren L. Knishevskaya 《International Journal of Infrared and Millimeter Waves》2000,21(7):1113-1117
In this paper we present a method to solve Maxwell's equations that enables to compute waveguide structure containing a semiconductor triangular prism. The numerical study has showed that the triangular prism in the waveguide has a wider frequency band in comparison with a square rod under equal conditions. The reflection coefficient dependencies on frequency, prism size and its permittivity have been computed. The algorithm and computer programme have been tested and compared with the numerical results and experimental data of the paper [1] with good agreement. 相似文献
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The propagation of electromagnetic waves in an antiferromagnetic material with the magnetoelectric effect is theoretically studied. The frequency dependences of the wavenumbers, dynamical permeability and permittivity, and reflection coefficient of electromagnetic waves for various energy parameters of the antiferromagnetic material have been obtained. It has been shown that there is a frequency range where the dynamical permeability and permittivity, as well as one of the wavenumbers, are simultaneously negative in the antiferromagnetic material with the magnetoelectric effect. In this case, the antiferromagnetic material is an example of a so-called left-handed medium. The reflection coefficient of electromagnetic waves from the surface of the antiferromagnetic material decreases anomalously in this frequency range. 相似文献
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The possibility of measuring the ultrasound attenuation coefficient and its frequency dependence in a one-side accessible
medium is considered under the assumption that the medium contains reflectors with unknown reflection coefficients and the
measurements are performed in the reflection geometry. The possibility of measuring the reflection coefficients themselves
is indicated. All the above parameters can be measured even when the reflector has the form of a layered structure. 相似文献
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介绍了一种简易测定柔性材料线胀系数的实验装置和测量方法.利用原有FD-LE线膨胀系数测定仪,使用圆珠笔中的弹簧、笔芯和笔头制作了材料和千分表的连接装置,并利用改进后的仪器测量了几种柔性材料的线胀系数. 相似文献
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D. A. Usanov A. V. Skripal A. V. Abramov A. S. Bogolyubov M. Yu. Kulikov D. V. Ponomarev 《Technical Physics》2010,55(8):1216-1221
Computer simulation and experimental study of the frequency dependences of the transmission and reflection coefficients of
photonic crystals based on a microstrip structure are carried out in the case when the periodicity of the structure is violated
by a change in the permittivity of the substrate of one of the alternating segments of the microstrip line. A method is developed
for measuring parameters of the material playing the role of inhomogeneity in the open microwave photonic structure. The complex
permittivity is determined for a number of polar and nonpolar liquids. 相似文献