基于传输反射法的等离子体相对复介电系数测量

为解决微波激发等离子体参数诊断存在的困难问题,提出利用二端口传输反射法测量微波激励产生的低温等离子体的等效相对复介电系数。使用有限元方法设计了基于BJ22标准波导的样品测试结构,该结构能在较大的介电系数范围内,保证介电系数和端口的|S11|,φS11和|S21|参数保持较好的单调性,避免产生多值问题;通过人工神经网络对计算获得的各介电系数对应的S参数进行训练,达到足够的精确度;最后通过实验,将测量获得的S参数利用神经网络反演获得待测物质的相对复介电系数。该方法对今后测量类似等离子体、复介电系数实部为负的特殊材料的介电常数具有一定的指导意义。     

微波频率下乙酸乙酯皂化反应等效介电系数的实验研究

微波化学研究中的关键问题之一是对化学反应过程中的介电系数进行跟踪和测量.本文采用开槽同轴谐振探头首次测量了乙酸乙酯皂化反应对微波的反射系数,并用遗传算法获得了微波频率下该反应的等效介电系数.结果发现等效介电系数实部随温度的变化趋势符合L Onsager和Debye理论对极性混合溶液的描述;等效介电系数虚部因极化损耗和欧姆损耗随温度变化而相应变化;而等效介电系数实部随时间的变化与L Onsager极性混合溶液等效介电系数理论的描述相反.     

用复合谐振腔法测量介质谐振器材料的介电特性

本文根据Barlow提出的在TE(01n)模谐振腔上耦合一段截止波导构成复合腔的原理，首次在C波段对介质谐振器材料的介电性能进行了测量，并从理论上证明了该方法对相对介电系数有很高的测试灵敏度，本文给出了几种介质谐振器材料的测试结果，最后就样品厚度对测试精度的影响作了分析。     

用复合谐振腔法测量介质谐振器的介电特性

本文根据Ｂａｒｌｏｗ提出的在ＴＥ０１ａ模谐振腔上耦合一段截止波导的构成复合腔的原理，首次在Ｃ波段地介质谐振器材料的介电性能进行了测量，并从理论上证明了该方法对相对介电系数有很高的测试灵敏度，本文给出了几种介质谐振器材料的测试结果，最后就样品厚度对测试精度的影响了分析。     

微波冶金反应器加热效率与均匀性优化

含锆型硅酸铝纤维板(zirconium aluminum silicate fiberboard, ZAF)作为保温炉衬在微波冶金反应器内的设计和安装常常是以经验为主,通常存在加热效率低、加热均匀性差等问题,难以满足实际工业生产要求。文章首先采用谐振腔微扰法测量了ZAF在2450 MHz频率下25～1000℃温度范围内的介电参数;采用激光闪射法测量了其在25～500℃范围内的导热系数;基于数值模拟技术探究了保温炉衬厚度变化对腔体内反射损耗S₁₁、电场、温度场和功率损耗等参数的影响。结果表明：ZAF的介电参数在700℃之后明显增大,导热系数在100℃之后随温度呈线性增加;保温炉衬的结构参数对负载的加热效率和均匀性具有重要影响,当保温炉衬厚度为60 mm时(方式3),谐振腔内负载的加热效率最高,在300 s时的平均温度为751.9℃,总吸收效率高达88.5%。     

无损测定成品带线基片的复介电系数

用谐振腔法无损测定两种进口带线基片成品的复介电系数。本工作的特点是用若干书已知介电系数的材料，制作成形状、尺寸与待测基片一样的标准样片，将待测基片与样片引起的不同频差着作为介电系数微扰，用插值法求得待测基片的介电系数。     

保偏光纤环形谐振腔研究

报道了一种用于角速度测量的光纤谐振式传感器保偏光纤环形谐振腔的研究,给出了测量的原理、实验装置和实验结果.根据计算和实验结果,对影响系统性能的几个重要光学参数进行了设计和优化.该谐振腔已在传感器系统中得到应用.     

基于布里渊和瑞利散射光拍频的方法测量温度

基于光纤非线性效应,设计并搭建出一套布里渊散射光与瑞利光拍频测量温度的实验装置,用布里渊频移量对温度系数进行标定,并采用三种不同方法进行数据处理,结果表明采用频移量均值线性拟合结果较好,得到的布里渊温度频移系数为1.005 MHz/℃,该温度传感系统的测量精度为0.7 ℃。     

铁电材料相变温度自动测试仪

铁电材料相变温度的测量一般采用电桥法,即测量铁电材料介电系数随温度的变化,由介电系数的转折温度来确定相变温度。但电桥法测量常常碰到一些困难:第一,有些铁电材料相变温度较高,在高温时电导较大;有些铁电材料在接近相变温度时损耗已超出电桥测量范围,使电桥无法平衡,不能确定其相变温度。第二,大部分手控电桥不备有线性电压输出,     

一种交联型光学聚合物的电光特性及其稳定性

对一种交联型非线性光学聚合物的电光特性及其稳定性进行了研究.通过交联反应将生色团分散红DR19连接到高聚物纤维素二醋酸酯(CDA)可合成得到该交联电光聚合物,交联反应温度为164 ℃.采用带栅极偏置的电晕极化系统对旋涂制备的聚合物薄膜样品进行极化处理,极化电压为8 kV.极化处理后的样品具有较好的电光特性,采用Mach-Zehnder干涉仪测量系统测得样品在1 550 nm处电光系数为4.80 pm/V.通过电光系数和介电驰豫测量研究了交联体系的稳定性,与掺杂型电光聚合物相比,该交联电光聚合物具有很好的长期稳定性,平均驰豫时间达到5.3 years,二阶非线性驰豫遵循KWW规律.介电分析结果显示驰豫时间的温度特性满足Arrhenius规律.     

Measurement system of complex permittivity of ornamental rocks in L frequency band

The use of ground-penetrating radar (GPR) techniques at high frequencies for historical building investigations requires an accurate knowledge of the material complex permittivity. A new measurement system is presented, which by exploiting a resonance phenomenon, yields accurate values of permittivity and resistivity also in the case of low-loss materials. These parameters are obtained from an amplitude-only measurement of the transmission response curve of a rectangular waveguide cavity, loaded by the sample under test. The setup requires the availability of brick-shaped samples, which can be obtained easily in the case of rock materials. Permittivities and resistivities were measured in the frequency range 1.1-1.7 GHz on samples of marbles, sandstones, and limestones. The measurement method and the experimental results are presented and discussed.     

Dielectric property measurement using a resonant nonradiative dielectric waveguide structure

This letter describes a new dielectric characterization technique, based on the resonant nonradiative waveguide structure described by Yoneyama and Nishida , for permittivity measurements at microwave and mm-wave frequencies. The measurement system is modeled as a resonator comprised of two parallel conducting plates with a rectangular dielectric slab sandwiched in-between. Resonant frequencies of the longitudinal section electric (LSE) modes and the unloaded Q of the cavity are used to determine the permittivity of the dielectric and its loss tangent, respectively. The technique is shown to be accurate for measuring the dielectric properties of a wide array of polymer and oxide materials. For materials with small dielectric loss tangents, an accuracy of better than /spl plusmn/0.4% is attained in the measurement of the relative dielectric constant of the material.     

改进矩形腔微扰法测试微波电介质复介电常数

本文讨论了测试电介质微波复介电常数的矩形腔微扰法。对介质样品加载后的ＴＥ１０ｎ模矩形腔腔内场进行了理论分析。通过对腔内场的数值求解，得出了与微扰公式相似的、已修正的准确计算公式。     

Measurements of Permittivity, Dielectric Loss Tangent, and Resistivity of Float-Zone Silicon at Microwave Frequencies

The complex permittivity and resistivity of float-zone high-resistivity silicon were measured at microwave frequencies for temperatures from 10 up to 400 K employing dielectric-resonator and composite dielectric-resonator techniques. At temperatures below 25 K, where all free carriers are frozen out, loss-tangent values of the order of 2times10^-4 were measured, suggesting the existence of hopping conductivity or surface charge carrier conductivity in this temperature range. Use of a composite dielectric-resonator technique enabled the measurement of materials having higher dielectric losses (or lower resistivities) with respect to the dielectric-resonator technique. The real part of permittivity of silicon proved to be frequency independent. Dielectric losses of high-resistivity silicon at microwave frequencies are mainly associated with conductivity and their behavior versus temperature can be satisfactory described by dc conductivity models, except at very low temperatures     

On RF material characterization in the stripline cavity

We examine the accuracy of the air-filled stripline cavity in measuring the dielectric and magnetic properties of bulk materials in the frequency range of 150-2000 MHz. Measured data on complex permittivity and permeability for several different-sized specimens of dielectric and magnetic materials were compared with reference values obtained using other techniques of known uncertainties. Major differences were noted for both complex permittivity and permeability data, and we largely attribute these to less-than-optimal perturbation of the internal cavity fields by the material specimens under test. The technique is particularly unsuited to measuring the dielectric loss of the higher-permittivity low-loss materials due to energy scatter by the specimen under test. In order to improve measurement accuracy, we suggest guidelines on the range of specimen electric and magnetic volume needed for optimal cavity perturbation     

An automated 60 GHz open resonator system for precision dielectricmeasurements

An automated open resonator system was designed and constructed for precision measurement of the loss tangent and dielectric permittivity of low absorbing materials at 60 GHz. The use of a high-Q hemispherical Fabry-Perot cavity together with highly stabilized synthesized phase-locked Gunn oscillator sources and a superheterodyne receiver made it possible to measure loss tangent values as low as 10 μrad. Both cavity length variation and frequency variation techniques were utilized to provide precise data     

Automatic Digital Method for Measuring the Permittivity of Thin Dielectric Films

One of the most promising techniques for measuring the electric permittivity at microwave frequencies of thin dielectric materials of the order of 0.1 to 10 /spl mu/m, is the cavity perturbation method. For thin films of this type, it is necessary to determine accurately and display small changes in the resonant frequency and Q factor of the cavity in the presence of the material sample. A circuit for the simultaneous measurement and digital readout of the resonant frequency and Q factor of microwave cavity is described. For the resonant frequency measurement, a very efficient automatic frequency circuit, with a homodyne modulation-detection bridge and frequency stabilization loop, is applied. Theoretical analysis and experiments results with this circuit show that an accuracy of 5x10/sup -7/can be achieved in the resonant frequency measurement. For measuring the Q factor, two similar circuits are described. The technique is based on measuring the phase shift of the envelope of an amplitude modulated microwave signal when this signal is transmitted through a resonant cavity at resonance. Although an accuracy of 0.5 percent in the Q factor can be achieved, it is shown that the main limiting factor in both circuits is the accuracy of phase shift determination at RF frequencies.     

Extended cavity perturbation technique to determine the complexpermittivity of dielectric materials

An improved measurement technique to determine the complex dielectric properties of materials has been developed that extends the validity of the conventional cavity perturbation technique for circular cylindrical rod-shaped samples in circular cylindrical cavities resonating in TM_0n0 modes. The method is particularly useful for the dielectric characterization of fragile, low-loss materials that are difficult to machine to typically required thin dimensions. The method further allows for multi-frequency measurements using higher-order radial modes and somewhat alleviates the very small cavity dimensions typically required by the conventional perturbation technique at higher microwave frequencies. A validity criterion for the extended method is given. Measurements of the complex permittivity of NaCl single crystals are presented, showing excellent agreement with theory     

A simple method for accurate loss tangent measurement ofdielectrics using a microwave resonant cavity

A simple yet rigorous method has been developed to enable the loss tangent of dielectrics, having a known relative permittivity, to be accurately measured using a waveguide resonant cavity. The novel method eliminates the need for any physical measurement, either on the cavity or dielectric sample under test. The only electrical parameters that need to be measured are resonant frequencies and Q-factors of a reference cavity and those of the same cavity loaded with the dielectric sample. One of the advantages of the new technique is that dielectrics, of arbitrary shape, can be characterized at very high microwave frequencies. The new method has been verified through measurement over X-band     

Open Resonator System for Automatic and Precise Dielectric Measurement at Millimeter Wavelengths

As low loss dielectric materials, ZnS, MgF₂, MgAl₂O₄ and quartz ceramic have a very important application at millimeter frequencies. However, there is little information about their dielectric properties in the millimeter wavelength band. To obtain their dielectric properties, an automatic open resonator measurement system at Ka-band is designed and constructed. The importance on the precision determination of cavity length over a broad band and the checking of a measurement system are emphasized and their solutions are put forward in this paper for the first time so far as we know. The solutions of above problems ensure the credibility and high accuracy of our measurement system. The certified measurement system after a series of checking is used to measure the above materials. Lots of measurement results show that the standard deviation of measurement error is less than 0.154% in permittivity and 20.42% in loss tangent. Meanwhile, some experimental summaries on the open resonator technique are provided. Software that controls the measurement system is developed and it improves the testing efficiency greatly.