Microwave Measurement of Dielectric Properties of Low-Loss Materials by the Dielectric Rod Resonator Method

Improvements both in accuracy and speed are described for the technique of measuring the microwave dielectric properties of low-loss materials by using a dielectric rod resonator short-circuited at both ends by two parallel conducting plates. A technique for measuring the effective surface resistance R/sub s/ of the conducting plates is proposed to allow the accurate measurement of the loss tangent tan delta. By means of the first-order approximation, the expressions are analytically derived for estimating the errors of the measured values of relative permittivity epsilon/sub r/, tan delta, and R/sub r/, for measuring the temperature coefficient of epsilon/sub r/, and for determining the required size of the conducting plates. Computer-aided measurements are realized by using these expressions. It is shown that the temperature dependence of R/sub s/, should be considered in the tan delta measurement. The copper plates used in this experiment have the relative conductivity of 91.0+-2.7 percent at 20°C, estimated from the measured R/sub s/ value. For a 99.9-percent alumina ceramic rod sample, the results measured at 7.69 GHz and 25°C show that epsilon/sub r/,= 9.687+-0.003 and tan delta = (1.6+-0.2)x 10/sup -5/. The temperature coefficients measured between 25 and 100°C are 112x10/sup -6//°C for epsilon/sub r/, and 23x10/sup -4//°C for tan delta.     

微波介质陶瓷材料介电性能间的制约关系

微波介质陶瓷材料的三个主要参数相对介电常数εr、品质因数Q和谐振频率温度系数之间存在一定的关系。采用一维双原子线性振动模型,分析了微波介质陶瓷材料的εr、Q影响因素和它们之间的相互制约关系;采用Clausius-Mosotti方程,分析了谐振频率温度系数的影响因素以及它和εr之间的相互制约关系。讨论了提高高介微波介质陶瓷材料性能的途径,发现采用同电价质量较轻的离子取代,在基本不影响介电常数的情况下具有提高材料的Q·f值的可能性。     

Circuit Properties of Microwave Dielectric Resonators

The purpose of this paper is to present experimental data on the circuit properties of dielectric resonators which do not have conducting boundaries. The resonators are constructed of single-crystal rutile and strontium titanate, which, as has been shown by several authors, can form resonators of miniatnre size and high unloaded Q. We consider the lowest-order H mode, give measured values of resonant freqnency (for rectangular parallelepipeds), mechanical frequency tuning, control of coupling to microwave circuits, and discuss the measurement of, and typical values of, external Q of resonators mounted in waveguides. We also consider periodic propagating circuits consisting of linear arrays of mutually coupled resonators.     

微波介质材料与器件的发展

详细论述了微波介质材料与器件国内外现状和技术发展趋势, 分析了应用前景和国内市场需求,对我国“十一·五”发展方向和重点研究课题提出了建议。     

The Dielectric Properties of Wet Materials

In microwave remote sensing, knowledge of the dielectric properties of the materials observed (vegetation, soils) is important for the interpretation of the recorded reflection or emission and for the design of models for this reflection or emission. Although there exists no simple law which describes the properties of a heterogeneous system when the properties of its components are known, boundaries can be indicated for the permittivity of such a system. Heterogeneous systems containing water, such as wet soils and plant material, have very complex dielectric properties due to the role of the conductivity. However, at the higher microwave frequencies, in particular above the S-band, these conductivity effects play only a minor role and the free water is most important. When knowing the permittivity of wet materials the penetration depth can be determined. In all practical cases this depth is smaller than the wavelength used for the observations.     

微波陶瓷介电性能自动测试系统设计

开路型微波陶瓷材料介电性能自动测试系统的设计包括系统的测试原理、系统硬件和软件组成。利用操作界面友好的自动测试程序,可在程序面板上控制网络分析仪,实现测试数据的实时采集、分析计算与显示存储,从而提高测试效率与精度。实测表明,利用该系统能对高介电常数、低损耗的微波陶瓷材料复介电常数进行快速、准确、无损的自动测试。     

BiVO4掺杂对CLST介质陶瓷介电性能的影响

采用传统陶瓷工艺制备了BiVO4掺杂的CaO-Li2O-Sm2O3-TiO2(CLST)介质陶瓷,用X-射线衍射仪、扫描电镜及电感-电容-电阻测试仪等对其烧结特性、相结构及介电性能进行了系统研究.结果表明,BiVO4掺杂能显著降低CLST陶瓷的烧结温度,由1 300 ℃降至1 200 ℃.BiVO4掺杂量为1%,烧结温度为1 200 ℃时,CLST陶瓷具有较好的综合介电性能:εr＝88,tan δ＝0.018,τ f =-30×10-6/℃.     

LTCC材料介电性能的影响研究

文章研究了La2O3-B2O3和SiO2作为添加剂对钙硼硅系LTCC材料的烧结和介电性能的影响。实验结果表明,La2O3-B2O3添加剂促进了CaSiO3的析晶,从而极大增强了钙硼硅玻璃陶瓷的抗弯强度。Si用于调节样品的收缩率以满足实际生产要求。CaO-B2O3-SiO2-6wt%La2O3-B2O3-7wt%Si样品性能较好：εr=6.13,tanδ=12.34×10-4（10 GHz）,弯曲强度σf≥160 MPa,收缩率为14.9%。     

BBS玻璃掺杂对CLST陶瓷介电性能的影响

采用传统陶瓷工艺制备了BaO-B2O3-SiO2(BBS)玻璃掺杂的CaO-Li2O-Sm2O3-TiO2(CLST)介质陶瓷,用X-射线衍射仪,扫描电镜及电感-电容-电阻测试仪等对其烧结特性、相结构及介电性能进行了系统研究.结果表明,BBS掺杂能显著降低CLST陶瓷的烧结温度,由1 300℃降至1 100℃.BBS掺杂量为7%(质量比),烧结温度为1 100℃时,CLST陶瓷具有较好的综合介电性能:介电常数εr=62,介电损耗tan δ=0.007,频率温度系数τf=0.82×10-6/℃.     

Helical Resonators for Measuring Dielectric Properties of Materials

A theoretical and practical investigation is given of superconducting helical resonators with quality factors greater than 10/sup 8/ which allow the determination of dielectric loss tangents in the frequency range of 0.1 to 5 GHz and below 15 K with high accuracy. The underlying measurement theory is an extension of perturbation theory. They are evaluated for the fields in a shielded multiple quarter-wave helical resonator with a cylindrical dielectric specimen inside the helix. Measurement results on optimized resonators made from superconducting Nb and Nb/sub 3/Sn are reported as well as further applications.     

钛酸锶钡电介质材料的显微结构和基本性能

钛酸锶钡（BSTO）铁电材料在微波和信息等领域具有很大的优势和潜力，该文综述了该材料的结构和基本介电性能方面的研究情况，并重点讨论了BSTO材料中的晶粒尺寸效应，最后对在电场和频率作用下材料的特殊性能进行了简单介绍。     

CNT对BST陶瓷微波介电性能的影响

采用XRD及SEM研究(Ca0.61Nd0.26)TiO3对微波介质陶瓷Ba4Sm9.33Ti18O54的结构和微波介电性能的影响。获得了一些性能较好的微波介质陶瓷(1–x)Ba4Sm9.33Ti18O54-x(Ca0.61Nd0.26)TiO3,其微波介电性能如下:εr=75,Q·f为8985GHz,τf为–8.2×10–6℃–1(x?=0);εr为75,Q·f为9552GHz,τf为–14.4×10–6℃–1(x?=0.2)。     

MnCO3掺杂对BMT陶瓷介电性能的影响

采用传统电子陶瓷工艺合成了MnCO3掺杂的Ba(Mg1/3Ta2/3)O3(BMT)微波介质陶瓷,并研究了MnCO3掺杂量对陶瓷微波介电性能的影响.实验结果发现,添加少量的MnCO3能改善BMT陶瓷的烧结性能,当w(MnCO3)=2%时,陶瓷致密化烧结温度由纯相时的1 650℃以上降至1 350℃,且表观密度提高到7.482 g/cm3以上,烧结体密度可达理论密度的98%,材料的微波性能达到最佳值:介电常数εr=25.09,品质因数与频率之积Q·f=99 000 GHz(8 GHz),谐振频率温度系数τf=0.5×10-6/℃.     

微波复合介质板的介电性能验证研究

以国外某公司的微波复合介质基板测试数据为参考,采用50Ω阻抗匹配电路测试了介电常数为2.94的某国产微波复合介质板在10 GHz下的驻波、插入损耗。测试结果表明,国产微波复合介质板的介电性能满足电路使用要求。高低温环境下的性能测试结果表明国内板材的一致性略逊于国外产品,仍需对制备工艺的稳定性、一致性进行改善优化。     

微带线法测量微波材料的复介电常数

电磁波传输介质的电磁参数的准确测量,对材料的实际应用十分重要。研究微波材料介电常数的微带线测量方法,通过正演和反演过程的求解分析,对不同介电常数的材料进行了实际计算,同时还对测试误差进行了简要分析。结果表明,微带线测试微波材料的复介电常数方法可行,测量过程较为简单,测量结果准确。     

结构参数对微波介质滤波器电性能的影响

利用Ansoft-HFSS仿真软件对微波介质滤波器进行建模及仿真,总结了结构参数对其电性能影响的变化规律,并提取了最优的器件结构参数.采用传统的电子陶瓷生产工艺制备样品,利用此规律指导器件的后期调试工作.结果表明,中心频率f0=2 493.0 MHz,插入损耗IL=1.539 dB,3 dB带宽BW3 dB=30.2 MHz,带内波动小于0.1 dB,在f0- 125 MHz外带外抑制Ls＞45 dB;在f0 +125 MHz外Ls＞65 dB,电压驻波比VSWR＜1.2.测试结果与仿真结果吻合,验证了该规律的可行性和正确性.     

Microwave Dielectric Properties of Ceramic and Nanocomposite Titanates of Transition Metal

Ceramic and nanocomosite samples of the titanates of transition metals have been synthesized and their microwave dielectric properties have been investigated. Frequency and magnetic field dependences of the transmission and reflection coefficients in centimeter and millimeter wavebands were measured. It is established for most of studied ceramic titanates that transmission coefficient increases and reflection coefficient decreases when frequency increases. An absorption maximum has been found for ceramic sample made of Co_0.9Fe_0.1TiO₃. The real and imaginary parts of complex dielectric permittivity were determined from measurements of transmission and reflection coefficients. On the whole, real part of dielectric permittivity of nanocomposite titanates based on an opal matrix is less than for ceramic titanates.     

MgO-TiO_2-CaO系统介电性能的研究

首先研究了不同组成的MgO-TiO2-CaO(MTC)系统的介电性能。偏钛酸镁(MgTiO3)具有正温度系数。钛酸钙具有较大的负温度系数,用它来调整钛酸镁系统的温度系数以使其趋近于零。同时向系统中加入玻璃,玻璃在烧结中形成液相,加速MTC系统的烧结并改善其介电性能。获得了一种性能良好的零温度系数陶瓷材料。     

Substitution Method for Swept-Frequency Measurements of Dielectric Properties at Microwave Frequencies

A solid-state computer-controlled system has been used to make swept-frequency measurements of the insertion loss and reflectance of biological specimens and other media. A substitution procedure was used for direct comparison of samples to allow determination of small differences (on the order of 0.1 dB) in insertion loss and reflectance.     

甘氨酸硝酸盐法合成LaAlO3及其微波介电性能

采用甘氨酸-硝酸盐法(GNP)合成了LaAlO3钙钛矿氧化物,并采用差热-失重(DTA-TG)分析、X-射线衍射仪(XRD)和粒度分析等方法对产物的形成过程和粉体性能进行了研究,用阿基米德排水法和网络分析仪分别研究了烧结体的烧结性能和微波介电性能。结果表明,采用GNP可在700℃的低温下合成单相LaAlO3粉体钙钛矿氧化物,其晶格常数为:a=b=0.536 4 nm,c=1.311 6 nm,α=β=90°,γ=120°。合成粉体的晶粒尺寸(一次粒径)小于100 nm,二次粒径约为2μm。1 500℃烧结12 h可获得相对密度达95.1%的LaAlO3陶瓷,具有良好的微波介电性能:rε=23,Qf=38 000 GHz。