薄膜材料的微波复介电常数测量

为了精确测量厚度在以1 μm以下薄膜材料的微波复介电常数,提出一种基于金属谐振腔微扰理论的测量方法和装置,对该方法进行了理论分析和实验验证,实验样品采用0.81μm厚度的MC-91(BaO-(SmNdLa)2O3-Bi2O3-TiO2)介质陶瓷薄膜,测试频率在2.4 GHz左右,对测量结果进行了误差分析,其相对误差＜7%,其中3%的误差是由薄膜厚度的测量误差引起的.     

六端口反射计测量复介电常数的改进方法

提出了六端口反射计测量介质材料复介电常数的一种改进方法,新的算法使测量面与参考面分离,消除了传统测量方法中测量面与参考面无法完全重合引入的误差.给出超越方程的简单准确的数值解法,得到了相对介电常数多值间隔与测量频率和样品长度的关系.实际测量结果表明本文方法的有效性和实用性.     

毫米波频段材料介电特性计量研究

系统地开展了毫米波频段材料复介电常数的测量方法研究.基于自由空间法采用两步校准方法和时域选通技术,实现了 75～110 GHz宽频范围内材料介电特性的测量表征,并基于准光Fabry-Perot谐振原理,研制具有高品质因数的开放式谐振腔,利用高斯波束理论建立了材料介电特性的反演模型,尤其适用于低损耗介质材料的准确测量.通...     

基于VC++的介质复介电常数带状线法自动测试系统的研究

随着微波技术的迅猛发展,对微波介质材料提出了新的要求,对介质材料的各种性能的测量有了更多的需求,复介电常数是介质的一个主要参数,本文就微波介质复介电常数测量的带状线法进行了一个简单的介绍,并重点就基于VC++所编制的自动测量程序做了相关的论述。自动化测量可以大大提高我们的工作效率。     

手性材料手性参数的圆波导测量方法

本文提出了用普通微波圆波导测量系统测量了手性材料复手性参数的方法。该方法还能同时测量手性材料复介电常数和复磁导率。为了得到手性参数,首先需要测量短路和开路时的复反射系数,及电磁波通过手性材料后的偏转角和轴比。测量结果与自由空间法的测量结果一致。     

测量介质材料复介电常数的准光腔法

针对介质材料,介绍了在毫米波段和亚毫米波段能够准确测量其复介电常数的准光学谐振腔法。准光学谐振腔具有高Q值、使用简便、样品放置容易等许多优点,能够有效地完成介质材料电介质参数精密测量的任务。这种谐振腔为半球型并由一个平面镜和一个凹面铜镜组成,采用固定腔长法或固定频率法进行测量。另外,还介绍了准光学谐振腔的测试系统和最新的研究成果及改进方法,例如测量多层薄膜及在更高频段的测量方法。     

微扰和标定技术测量薄膜微波介电常数

提出了一种测量介质薄膜微波段介电常数的方法.该方法基于金属空腔谐振器微扰理论,用已知介电常数的基片作为标样,标定测量系统的有关参数,然后分别测量空腔、基片插入空腔、镀有介质薄膜的基片插入空腔三种情况下的谐振腔谐振频率,计算出镀覆于基片上介质薄膜的微波复介电常数.本文SiO2和MgTiO3-CaTiO3(MCT)介质陶瓷薄膜作了实验测量验证,结果表明该方法具有良好的测量精度(小于6%).     

谐振法测量圆管状样品复介电常数典型结构的解析模型

针对圆环形介质元件制作在线监测的需要,提出用谐振法直接测试圆管状绝缘介质复介电常数的思路。提出4种可能的谐振结构形式,其中推演介质加载圆柱腔TM010模式谐振的解析模型,深入分析国外文献关于介质加载圆柱腔TE011模式谐振问题的理论结果,并对介质加载圆形同轴腔的特性方程用于复介电常数测量的问题进行探讨。对各个解析模型进行计算,并相应地与文献的实验结果进行对照,吻合良好。结果表明:TM010模式的解析模型正确;谐振特性参数对加载介质复介电常数(εr=1~80,tanδ=10~(-5)~10~(-4))的敏感性随结构的不同而不同。最终得出:圆柱腔TM010模式可用在谐振法测试圆管状绝缘介质元件的复介电常数中。     

基于谐振法测试微波介质材料的介电参数

介电常数是介质材料的主要性能参数之一,该文讨论了微波介质的介电参数的理论计算,分析了谐振法的模型,研制了基于谐振法测量微波介质材料介电参数的测量系统.通过对多个样品进行实测,结果表明与参考值比较吻合,评价了该测量系统测量结果不确定度,从而建立了微波频段内微波介质材料介电常数测量平台.     

传输/反射法测量固体复介质材料介电常数

介绍/传输反射法测量固体介质材料复介电常数等关键技术难点,通过建立固体介质材料的介电谱和磁谱测量装置,开展复介电常数、复磁导率、复损耗角正切测量技术研究,在30 MHz～18 GHz采用空气线同轴传输的方法、在18～50 GHz采用三段波导传输的方法,实现了30 MHz～50 GHz全频段固体介质材料电磁参数的测试能力,提出了复介电常数、复磁导率、复损耗角正切测量的数学模型,编制了材料测试软件,实现了同轴和波导的全频段测量。     

A methodology for determining complex permittivity of construction materials based on transmission-only coherent,wide-bandwidth free-space measurements

An integrated methodology for determining the unique combination of complex permittivity based on measured transmission coefficient and time difference of arrival (TDOA) information in free-space measurements is proposed. The methodology consists of an estimation procedure of the real part of complex permittivity based on TDOA, and a root-searching procedure based on parametric system identification (SI) together with an error sum of squares (SSE) criterion. Generally, non-unique combinations of dielectric constant and loss factor are encountered when lossy or low-loss materials are measured and the proposed methodology is aimed at the determination of unique combinations of dielectric constant and loss factor for such materials. The proposed methodology is validated by measurements of several materials with known dielectric properties. The estimated complex permittivity values for Teflon, Lexan, Bakelite, and concrete are in good agreement with those reported in the literature. The method has potential for in-situ measurement of dielectric properties for construction materials. Applicability and limitations of the methodology are discussed.     

A Quasi-Optical Free-Space Measurement Setup Without Time-Domain Gating for Material Characterization in the W-Band

In this paper, a new free-space measurement setup at millimeter waves for material characterization is presented. Using specific Gaussian optics lens antennas and a thru, reflect, and line calibration, the setup provides the free-space four S-parameters over the W-band of planar dielectric slabs without time-domain gating. An efficient optimization procedure is implemented to extract complex permittivity from the four S-parameters of homogeneous dielectric materials. Nonhomogeneous materials can also be tested, and measurements are presented. Very good agreement is observed between simulated and measured four S-parameters of various dielectric plates. Thanks to this new specific calibration and measurement procedure, automation of the test bench is easily achieved     

Reliable method for material characterisation using quasi-optical free-space measurement

An extension to the Nicolson?Ross?Weir (NRW) algorithm to retrieve complex permittivity and permeability from both reflection and transmission coefficients is presented. This new numerical retrieval approach solves the phase ambiguity problem associated with the NRW algorithm. A free-space quasi-optical two-port measurement setup is employed to obtain the scattering parameters of different samples in the W-band frequency range. The results of different samples with various thicknesses are presented. The advantages and limitations of the method are also discussed.     

Lossy multilayer channel optical waveguides analyzed by the transmission line matrix method

We demonstrate that the three-dimensional vectorial transmission line matrix (TLM) method is applicable to the analysis of lossy multilayer optical waveguiding structures. Any lossy multilayer waveguide geometry, including sharp discontinuities in the transverse plane, can be treated taking into account the coupling between all optical field components. The complex propagation constants (propagation constants and the attenuation coefficients) for the fundamental TE-like and TM-like modes can be determined. These parameters of the fundamental TM-like mode of a typical lossy multilayer rib dielectric waveguide are obtained as functions of free-space wavelength. Calculation of the electric-field pattern is also included. Numerical comparisons with the argument principle method (for the case of lossy multilayer slab waveguides) and the spectral-index technique (for the case of lossy multilayer rib waveguides) are also included, and it is shown that the application of the TLM method to lossy multilayer optical waveguides is accurate.     

Free-space measurement of complex permittivity and complexpermeability of magnetic materials at microwave frequencies

A free-space measurement system operating in the 8.2-40-GHz frequency range is used to measure the reflection and transmission coefficients, S₁₁ and S₂₁, of planar samples. The complex electric permittivity and the magnetic permeability are calculated from the measured values of S₁₁ and S₂₁. The measurement system consists of transmit and receive horn lens antennas, a network analyzer, mode transitions, and a computer. Diffraction effects at the edges of the sample are minimized by using spot-focusing lens antennas. Errors due to multiple reflections between antennas via the surface of the sample are corrected by using a free-space TRL (thru, reflect, line) calibration technique. For thin, flexible samples, the sample had to be sandwiched between two half-wavelength (at mid-band) quartz plates to eliminate sagging. Results are reported in the frequency range of 8.6-13.4 GHz for materials such as Teflon, sodium borosilicate glass, and microwave-absorbing materials     

自由空间法测量复合材料复电磁参数

自由空间法可以方便地改变入射电磁波的角度和极化方向, 适用于测量复合材料的电磁参数。对自由空间法测量复合材料电磁参数进行了初步研究, 探讨了测量结果在计算过程中产生的多值问题, 并通过理论分析给出了一些有效的解决方案。用自由空间法测量了4种聚合物复合材料样品在X波段(8.2~12.4GHz)的复电磁参数, 并用波导测量法进行了验证。研究结果表明自由空间法测量复合材料电磁参数具有较高的精确度。      

Nondestructive Measurement of Materials Using a Waveguide-Fed Series Slot Array

The reflection from an array of narrow series slots on the broad face of a rectangular waveguide is used to determine the permittivity of lossy materials. The theoretical study of the electromagnetic field in the vicinity of the slots yields a system of integral equations which takes into account the internal and external coupling between slots. The numerical solution is discussed and an optimization procedure for the array is presented, which provides a simple relationship linking the reflection coefficient to the complex permittivity over a specified range. Computed results are compared to experimental values for air and a lossy dielectric at 10 GHz, showing good agreement. Interpolation from computed data is provided by a polynomial expansion: this allows one to determine the complex permittivity once the reflection factor has been measured.     

Permittivity determination of liquid materials using waveguide measurements for industrial applications

There is a need for a simple and relatively inexpensive microwave method for complex permittivity, ?, determination of liquid materials in industrial applications. Measurement cables that connect the measurement cell to the measuring instrument (usually a vector network analyser) may be either subject to severe phase instability particularly if they are long or metrology-grade cables are not available, or subject to thermal variation. In these instances, calibration techniques based on complex scattering parameter measurements may drastically suffer from extension of the reference plane to the boundaries of the measurement cell or sample end surfaces. In such situations, amplitude-only methods based on simplified calibration techniques such as response calibration are appropriate and very feasible. These methods have applications in industry such as thickness measurement and disbonding and delamination detection. The motivation of this study is to investigate a suitable method for ? determination of liquid materials using amplitude-only waveguide measurements. The analysis is restricted to lossy dielectric materials, which possess large enough attenuation such that the multiple reflections between their two end surfaces can be neglected. We derived an equation in terms of the loss tangent of these materials for selecting a suitable material thickness. We presented two approximations (frequency-independent and power-series representation) for ? determination of these materials. For validation of the method, we measured the ? of methanol and commercially available antifreeze solution by our method using a simple (frequency response) calibration and by another waveguide method using the thru-reflect-line calibration.     

A grounded coplanar waveguide technique for microwave measurement of complex permittivity and permeability

We present a method for extracting the complex permittivity and permeability of dielectric/magnetic thin films in a grounded coplanar waveguide configuration. The technique is applicable for extraction of these material parameters for lossy and lossless materials over a broad frequency range with high accuracy. For validation, we extracted complex permittivity and permeability, using the scattering parameters obtained from the full-wave electromagnetic simulation for two test cases over a frequency range of 5 to 15 GHz. Accuracy for both dielectric as well as magnetic materials is within 2% error.     

A free-space bistatic calibration technique for the measurement ofparallel and perpendicular reflection coefficients of planarsamples

A free-space bistatic measurement system suitable for operation in the frequency range of 5.85-40 GHz is calibrated to measure the parallel and perpendicular reflection coefficients of metal-backed planar samples for obliquely incident waves. The measurement system consists of transmit and receive antennas in the bistatic configuration, mode transitions, precision coaxial cables, and the network analyzer. Diffraction effects of the edges of the sample are minimized by using spot-focusing horn lens antennas, which focus most of the energy on a one-wavelength-diameter circular section of the sample. A new free-space bistatic calibration technique is developed to eliminate errors due to multiple reflections between transmit and receive antennas via the surface of the sample. The effect of defocusing due to the obliquely incident plane wave with focused antennas is minimized by introducing correction factors which modify measured reflection coefficients. Details of the calibration procedure and a discussion of the experimental results obtained for planar samples of Teflon and Eccogel 1365-90 in the frequency range 12.4-18 GHz are presented