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The following study investigates the use of a coaxial transmission line for determining the properties of powdery dielectric materials (1-10GHz). Four powdery materials with dielectric constants ranging from 3.5 to 70 (SiO$_2$, Al$_2$O$_3$, CeO$_2$, and TiO$_2$) were experimentally investigated at varying volume loading fractions. Powder particles were mixed with a paraffin matrix and properties of the powder were analyzed using ten mixing equations to verify their accuracy. These powder-paraffin composites were also modeled at varying volume loadings for comparison with experimental data to gain a better understanding of the interactions between the different phases. The optimal volume loading fraction was determined to be 10% for all powders tested. A metric for selecting the most well-suited mixing equation was proposed that involved taking the ratio of the particle dielectric to that of the matrix. This study ultimately provides guidance for experimentally measuring the dielectric properties of unknown powdery materials that have application for new devices that utilized powder-based dielectric materials.

This article describes a method for measuring the dielectric constant and magnetic permeability of alumina powder (corundum) in the frequency range of 8-12 GHz. The results of studies of permeability and permittivity using a segment of a coaxial transmission line depending on the size of corundum particles are presented.

Two coaxial transmission line methods have been compared in terms of precision in determining the dielectric properties of moist porous kaolinite samples. Equivalent measurement setups have been established to carry out analysis in the frequency range of a few MHz to 3 GHz. Results have been compared for samples ranging from 0% moisture content to 15% moisture content. The two methods show similar results for identical moisture contents. The four types of samples have constant dielectric values throughout the explored frequency range. A linear increase in permittivity has been found with increasing moisture content and sample density with both methods, as referenced in the literature.

In recent years, several papers have been published dealing with enclosed or surface-waveguides of elliptical cross section. Examples have included hollow metal waveguide, enclosed waveguide filled with one or more dielectrics, coaxial transmission lines, dielectric surface waveguides, and waveguides employing anisotropic media. Some of these types have been investigated experimentally, and several have been used in practical microwave-frequency applications, such as in feed lines for antenna installations.

The necessity to improve common electronic production technology and therefore meeting the trend to higher frequencies leads in the meantime to disproportional efforts. A promising disruptive technology to overcome these rising challenges are 3D printing processes. Despite the enormous availability of printable materials like varnishes or silicones, many of them are not yet specified concerning their radio frequency properties. Thus this work presents a simple and cheap coaxial transmission line method for an explorative screening of many different substances. Moreover the proposed method overcomes the problems of mechanical handling and chemical hardening of these materials. As a result it provides an accurate value for the relative permittivity and gives an estimation of the loss tangent at the same time for frequencies up to 8 GHz.

A novel method for complex permittivity and permeability measurements of dielectrics has been shown. The method is based on a previously developed transmission-line technique, however, has been modified to allow for dielectric properties estimation with measurements of reflections only. The analysis of measurement errors, resulting from: sample length uncertainty, vector network analyzer uncertainty, and open-end inaccuracy, has been shown in the article. The calibration method using open/short/offset-short standards has been described. The method has been experimentally tested by measurements of three different reference liquid samples. A good agreement between measured values and previously published ones has been obtained. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:727–732, 2014

Broadband dielectric measurement methods based on vector network analyzer coupled with coaxial transmission line cell (CC) and open-ended coaxial probe (OC) are simply reviewed, by which the dielectric behaviors in the frequency range of 1 MHz to 3 GHz of two practical geomaterials are investigated. Kaolin after modified compaction with different water contents is measured by using CC. The results are consistent with previous study on standardized compacted kaolin and suggest that the dielectric properties at frequencies below 100 MHz are not only a function of water content but also functions of other soil state parameters including dry density. The hydration process of a commercial grout is monitored in real time by using OC. It is found that the time dependent dielectric properties can accurately reveal the different stages of the hydration process. These measurement results demonstrate the practicability of the introduced methods in determining dielectric properties of soft geomaterials.

We present a methodology for characterization of soil relative dielectric permittivity in the frequency range 0.05–3 GHz. Soil samples are placed in a measurement cell constructed out of a EIA 1-5/8" coaxial transmission line, and then measured with a calibrated vectornetwork-analyzer. From these measurements the relative dielectric ermittivity is obtained by use of a modified Boughriet algorithm. In order to calibrate the vector-network-analyzer directly at the EIA 1-5/8" coaxial-transmission-line measurement lanes, we use the multiline through-reflect-line method. This method, while providing superior vector-network-analyzer calibration accuracy, is also easy to implement since it uses only transmission lines with known lengths and a single unknown highly-reflective termination. The implemented calibration method was compared to a simplified approach that uses the standard SOLT calibration in Type-N reference planes, and then accounts for the Type-N/EIA 1-5/8" adapters by removing their electrical delay. Experimental results for teflon and soil samples with different moisture content and salinity confirmed the validity of our approach. journal_title: Measurement Science and Technology article_type: paper article_title: 0.05–3 GHz VNA characterization of soil dielectric properties based on the multiline TRL calibration copyright_information: © 2017 IOP Publishing Ltd license_information: cc-by Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. date_received: 2016-07-20 date_accepted: 2016-10-26 date_epub: 2017-01-12 ispartof: Measurement Science & Technology vol:28 issue:2 pages:1-7 status: published

Precise knowledge of the absolute value and frequency dependence of the dielectric permittivity of ice is the basis for interpretation of radio echo sounding data on glaciers and ice sheets. However, in the range of radio-frequencies, data from direct measurements of the permittivity are sparse, and partially lacking uncertainty estimates. Here, we present new results for artificial and natural ice samples obtained by means of frequency-dependent measurements from 10 MHz to 1.5 GHz with a coaxial transmission line cell. Measurements on eight artificial ice samples grown from ultra-pure water within the cell yield a mean value for the real part of the relative permittivity of 3.18 ± 0.01 at − 20 °C. Sole evidence for dispersion is detected for frequencies below 10 MHz, possibly attributed to the Debye-type relaxation behavior. Investigation of the crystal orientation of the artificial ice samples reveals the c-axes to be predominantly parallel to the electric field inside the cell and allows to calculate a value representative for isotropic crystal orientation of 3.16 ± 0.01. Measurements on acid-doped artificial ice show a linear dependence of the real part with acidity with a gradient of (21.1 ± 3.9) [1/M]. The real part of the relative permittivity of natural firn and ice samples from a high Alpine glacier range from 2.02 at a density of 0.515 g/cm 3 to 3.08 at 0.875 g/cm 3 . Quasi-continuous measurements with the present setup on an alpine firn core are now possible, with resolution depending on the coaxial cell's length, for direct comparison with the established dielectric profiling method.

This paper presents the measurement technique that allows to determine the relative permittivity and permeability of powdered materials. Measurements are realized in a coaxial transmission line which guarantees the broad band frequency characterization. Calculations utilize the scattering matrix parameters of the two-port formed by the sample of powdered material supported by two dielectric walls. The proposed measurement procedure is demonstrated in the example of ferrite powder - Yiitrium Garnet YIG class ferrite for which the relative permittivity (@e^',@e^'') and permeability (@m^',@m^'') are determined in the frequency range of 200-1200MHz.

Time domain reflectometry (TDR) is commonly used for several monitoring applications, particularly in hydrology and soil science for soil water content evaluation. Furthermore, significant advantages of TDR methodology, such as its relevant performance characteristics in terms of high flexibility and high sensitivity, as well as a non-destructive detection approach, render this technique an appealing candidate for a variety of environmental and industrial applications. In a previous paper [A. Cataldo, L. Tarricone, F. Attivissimo, A. Trotta, Simultaneous measurement of dielectric properties and levels of liquids using a TDR method, Measurement, doi:10.1016/j.measurement.2006.11.006 ] the authors demonstrated that TDR can be successfully used for a simultaneous real-time qualitative and quantitative monitoring of liquids. In this paper, a rigorous metrological characterization of the proposed method is formulated, and the uncertainty contributions are identified. The obtained results, confirm that the system is definitely adequate for simultaneously measuring dielectric constants and levels of liquids, with the associated relative uncertainties of 2% and 3%, respectively, for all the considered liquid samples. This way, challenging perspectives for several monitoring applications are open, especially in the processing of industrial liquids.

In this article, mixtures of water and ethylene glycol, in which the concentrations of ethylene glycol are about 37%, 50%, 60%, and 70%, were used as the dielectric of coaxial transmission lines. The pulse breakdown strength, effective time to breakdown, relative permittivity, resistivity and freezing temperature of the mixture have been studied experimentally.

Time-domain-reflectometry (TDR) measurements, which were originally used to locate and diagnose faults in transmission lines, have been widely applied in geology and soil science for accurate and flexible measurements of soil moisture and water content. Furthermore, the most attractive advantages of TDR rely on the possible determination of the spatial location and nature of various objects, both in real time and with a nondestructive approach. This makes the TDR technique an appealing candidate for a variety of environmental and industrial applications. Although the TDR instruments are commonly used to date, particularly for the aforementioned purposes, the state of the art is rather lacking in liquid-monitoring applications. This paper describes how the suitable combination of TDR detecting functionalities can lead to a simultaneous monitoring of quantitative and qualitative properties of liquid samples. In fact, the proposed TDR method allows, in one shot, the measurement of liquid levels, the determination of multiple interfaces in layered media, and the evaluation of dielectric properties such as dielectric permittivity or electrical conductivity. Some applications to real cases are proposed, which are referred to petrol–chemical mixtures or water-based liquids, thus validating the approach on a wide range of materials.

In recent years, several calibration-independent transmission/reflection methods have been developed to determine the complex permittivity of liquid materials. However, these methods experience their own respective defects, such as the requirement of multi measurement cells, or the presence of air gap effect. To eliminate these drawbacks, a fast calibration-independent method is proposed in this paper. There are two main advantages of the present method over those in the literature. First, only one measurement cell is required. The cell is measured when it is empty and when it is filled with liquid. This avoids the air gap effect in the approach, in which the structure with two reference ports connected with each other is needed to be measured. Second, it eliminates the effects of uncalibrated coaxial cables, adaptors, and plug sections; systematic errors caused by the experimental setup are avoided by the wave cascading matrix manipulations. Using this method, three dielectric reference liquids, i.e., ethanol, ethanediol, and pure water, and low-loss transformer oil are measured over a wide frequency range to validate the proposed method. Their accuracy is assessed by comparing the results with those obtained from the other well known techniques. It is demonstrated that this proposed method can be used as a robust approach for fast complex permittivity determination of liquid materials.

In this paper, we compare analytical and optimizing reconstruction methods for the electrical permittivity of materials. The reconstruction is done from the measured S-parameters of a coaxial transmission line. We compare the different reconstructions on materials of known electromagnetic properties, air, and ethanol. We conclude that two methods, one analytical (propagation matrices) and an optimization (L/sub 1/ norm), are the most appropriate for the reconstruction of permittivities, whether these are low-loss and constant over the frequency range or highly lossy and frequency dependent.

In this article, we present a very simple toolkit for permittivity and permeability measurement in the microwave region in real time. This kit contains a coaxial cell and a dedicated software compatible with any Vector Network Analyzer (VNA) for the reconstruction of permittivity and permeability data. The customizing design of the coaxial cell depends on the applications and material forms. The dedicated software for overall cells reconstructs directly in real time the permittivity and the permeability from the S-parameters measured. The Nicolson & Ross-Weir algorithm is using after a de-embedding process done by modeling our cell with an identity card (IC). The novelty of our method is that, after calibration process of the VNA to remove the cable effect, the measurement of the permittivity and permeability were done directly after only one measurement in real time. To validate the accuracy of this new measurement process for new applications, we reconstruct the permittivity of two material forms (dielectric or/and magnetic solids, semisolid). This new toolkit is called EpsiMu (www.epsimu.fr). © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2643–2648, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25570

In this letter, we comment on the applicability of the derived characteristic equation (Eq. (7)) in a recently published article of Guoxin [Rev. Sci. Instrum. 86, 014704 (2015)]. To validate our comment, we first derive another characteristic function for determination of complex permittivity of dielectric materials for the configurations considered in the above article using calibration-independent uncorrected S-parameters for transmission-line measurements (coaxial-line, waveguide, free-space, etc). Unlike the characteristic equation in this article, the characteristic equation derived here for determination of the complex permittivity of liquid samples does not require any knowledge about the complex permittivity of plugs, used for holding liquid samples in place. We then performed 3-D full-wave simulations for the measurement configurations presented in Guoxin’s article for substantiation of the characteristic equation derived in this letter.

The complex permittivity of water is measured at 2.45 GHz and 10 GHz over the temperature range 10°C to 80°C using short circuited coaxial transmission line method. Water has high dielectric consta...

High-permittivity dielectric samples have been measured employing a transmission/reflection method in 7 mm coaxial transmission lines with an air-gap correction implemented that is based on a single-frequency measurement of these specimens using a TE01delta mode dielectric resonator technique. This allows an improvement of systematic uncertainties for high-permittivity materials.

In an electrically large square coaxial transmission line, we demonstrated preservation of a narrow impulse during propagation through a relatively tight 90° bend compensated by a layered approximation of a CID lens. By use of a non-linear global optimization algorithm, we established that the layered dielectric design was essentially optimal. In terms of the observed, raw impulse response, the compensated bend increased the pulse width by only 15 ps, to 70 ps, from the 55 ps observed for an equivalent length of straight transmission line. In contrast, without compensation, the transmission line bend distorted the impulse into a bipolar signal spread over a 500 ps time interval.

A 60 GHz mixer compatible with beam lead diodes using a novel circuit configuration incorporating dielectric loaded waveguide, stripline and coaxial transmission lines has been designed and fabricated. The mixer was developed for low-cost, high volume applications.

Presents the results from an analysis of a Martian soil simulant over the frequency range of 10 MHz to 1 GHz. The motivation is to provide an estimate of the electrical properties, complex permittivity and permeability, of a soil that can be expected on the surface of Mars. The test procedure involves measuring the reflection and transmission properties of the soil using a slotted section of coaxial transmission line. With the soil acting as the dielectric of the coaxial transmission line, four sets of measurements were collected using a network analyzer. These measurements include transmission through the soil and three sets of reflection measurements with the attached loads: short, open, and 50 /spl Omega/. Next, these measurements are compared to analytic values; these are calculated by representing the coaxial transmission line by a signal flow graph and assuming initial values of the permittivity and permeability. An iterative approach is then used to minimize the root-mean-square error and determine approximate values of the permittivity and permeability. Finally, the results are presented over the frequency range of interest.

The methodology developed by Siddiqui and Drnevich (1995) for measuring soil water content and density using Time Domain Reflectometry (TDR) was extended for routine use in the quality control testing of compacted soils. The objectives of the study were to develop computer software to automate data interpretation and data reduction, develop prototype equipment for field use, compare the results of the TDR method with the sand cone and nuclear density methods on actual construction sites and develop draft specifications for ASTM and AASHTO. New prototype equipment was developed for compaction quality control testing. Waveform interpretation and data reduction were automated by incorporating developed algorithms into a WindowsTM based computer program that is used on a palm top computer connected to the TDR apparatus. Over 150 laboratory and field tests were performed to evaluate the TDR equipment and procedure for use in the determination of moisture content and density of compacted soil.Under field conditions it was shown that the TDR method is more accurate than the nuclear density gage in estimating water content when compared to oven drying, with standard errors of 1.1% and 1.8%, respectively. The ability to assess the accuracy of the TDR method for determining density was limited because the true density of the compacted soil is not known. The sand cone test was used as a basis for comparing the TDR and nuclear density tests on several sites while accepting that the sand cone test is not an exact method. The time required to perform the TDR test under field conditions is approximately 15 to 20 minutes. The sand cone test can also be performed in approximately 15 minutes, while the nuclear density test can be performed in approximately two minutes. The time required to complete the TDR test relative to the nuclear density test, is viewed as its greatest limitation. In general, the nuclear gage provides estimates of density and water content much more rapidly than the sand cone or TDR tests, is less accurate than the TDR test in estimating water content, and must be calibrated for a specific soil using sand cone tests. Moreover, the nuclear gage uses a hazardous source requiring operators to take safety training and leading to expenses associated with equipment maintenance and disposal. The sand cone test is time consuming, and can not provide estimates of water content. The TDR test is also time consuming, but does provide accurate estimates of water content. At the present stage of the research, the TDR test has not shown great advantage in the measurement of water content and density relative to the nuclear density test. However, progress is being made in the development of an approach to use other features of the reflected waveform, in addition to the apparent dielectric constant, within the interpretation process. It is anticipated that the additional information that can be obtained from the reflected waveform will allow a more accurate estimate of density to be obtained while eliminating the need to...

Dielectric properties of grapes at 2.45 GHz were measured at moisture contents varying from 80 to 15% (wet basis) at temperatures ranging from 25-80 degrees C using the Open Ended Coaxial Transmission Line Technique. Both dielectric constant and loss factor decreased with decreasing moisture content. In low moisture samples these properties were found to be considerably influenced by higher temperatures. Dielectric properties of sugar solutions of varying concentrations (20-250% by weight in water) were also determined at different temperatures, and these values were compared to those of grapes of corresponding moisture concentration. Predictive models of the dieletric properties as functions of moisture content and temperature were generated using response surface methodology. The results are useful in estimating the volumetric heating of grapes by microwave energy, and these methods can be extended to sugar-based foods in general.

An attempt was made to confirm previous reports of resonant-like dielectric absorption of plasmid DNA in aqueous solutions at 1–10 GHz. The dielectric properties of the sample were measured using an automatic network analyzer with two different techniques. One technique used an open-ended coaxial probe immersed in the sample; the other employed a coaxial transmission line. No resonances were observed that could be attributed to the sample; however, resonance-type artifacts were prominent in the probe measurements. The coaxial line technique appears to be less susceptible to such artifacts. We note two important sources of error in the calibration of the automatic network analyzer using the probe technique.

The complex dielectric constant of highly purified nitrobenzene in the region of anomalous dispersion has been determined by measuring the input impedance of a variable length of a coaxial transmission line filled with the liquid. The measurements were carried out at frequencies from 0.65 kmcps to 3.00 kmcps in the temperature range between 15°C and 50°C. Good agreement was observed with an expression suggested by Cole and Cole, and the critical frequencies in this temperature region were found to be between 3 and 6 kmcps.

The theory and design of dielectric beads in a coaxial transmission line are discussed. At first the theory of many dielectric beads in a transmission line are discussed briefly. It is shown that by proper choice of the spacing between the adjacent beads the overall reflection produced by all the beads can be minimized. The case of an optimum bead producing minimum reflection is discussed in detail. Broadband characteristics of such a bead is also studied. Finally, the actual design of a bead is carried out.

A microwave instrument for non-destructive testing of the homogeneity of supercalendar rollers used in paper mills is described. The sensor consists of a flat coaxial transmission line a half wavelength long. A sensitivity of more than 0,1% is achieved in measuring small changes in the dielectric constant. Measurement of absolute values of the dielectric constant is also possible.

A theoretical expression is derived for the relative error on e′ and e′ when measured with the method of Roberts-von Hippel using coaxial transmission lines. This expression is shown to depend on the experimental accuracy of the measureable quantities but also on the characteristic parameters of the sample e′, e″ and its thickness h. Numerical calculations show how in various cases these errors change with h. It is also demonstrated that for polar samples the choice of the thickness of the sample may become critical. Some experimental results are given to illustrate this effect.

Measurements of the dielectric constant of soil containing different known percentages of moisture were made at a fixed frequency of 430 Mc/s. The method adopted involved the use of a coaxial transmission line terminated with a sample of the soil under test The line consisted of a central rod with a concentric tube about 2½ metres in length. Measurements were made with soil samples containing from 4.1% to 47.7% moisture The dielectric constant was found to vary from 4.0 to 31.4 The values are shown graphically and compared with those obtained by nine other authors. The conductivity could not be measured accurately with the method used, but it was estimated to vary from about 1 5 × 109 e.s u with 4% moisture to 4 × 1010 e.s u with 50% moisture

Numerical "shooting" methods are employed in obtaining the dispersion curves of a coaxial waveguide loaded with a radially inhomogeneous dielectric. The utility of this technique is tested by comparing results with known analytical solutions. The method is also used to find the dispersion curves of a coaxial waveguide loaded with a radially Gaussian-distributed plasma.

The theory underlying the measurement of dielectric constants and power Iactors, by means of resonant lengths of coaxial transmission line, is developed, apparatus used for such measurements is illustrated and the measurement routine described. A table of typical results is appended together withan “X tan X” table for aid in the calculations.

In a system where a number of transmission lines are fed from a common source, the phase relationship at the far end of the lines is determined by the electrical length of the transmission lines. This length is a function of the physical length and the dielectric constant of the line. Any variation in the dielectric constant or the physical length of the transmission line will cause a change in the electrical length and result in changed phase relationship at the far end of the line.

The recently introduced concept of one-dimensional subwavelength resonator, which comprises a combination of forward-wave material and backward-wave material, is investigated experimentally. The rectangular evanescent waveguide filled with negative permeability uniaxial meta-material based on capacitively loaded loop was used as backward-wave meta-material in 350 MHz band. The waveguide was interfaced with an ordinary (forward-wave) coaxial transmission line terminated with a sliding short. The overall length of this waveguide-coaxial structure was much shorter than the wavelength. The distribution of the phase of the magnetic field along the structures was measured with the help of a small loop antenna and network analyzer, for different settings of the sliding short. The measurement results proved that is possible to meet resonant conditions on the structure whose overall length is much smaller than a wavelength, as it was previously theoretically predicted.

Steel Fiber Reinforced Concrete (SFRC) is increasingly being used in civil constructions, especially precast tunnel segment linings. Fibers are mixed with fresh concrete, which results in a more or less random distribution of fibers within the concrete matrix. Because of this, SFRC demonstrates a great challenge when it is being investigated using GPR. In order to investigate the frequency-dependent dielectric parameters of SFRC; (I) PET/CT scans of concrete were conducted to understand the nature of orientation and density of fibers being distributed within the concrete sample and (Π) a two-port coaxial transmission line technique developed for the determination of dielectric spectra of undisturbed soil samples was used to investigate the concrete's complex permittivity with and without steel fibers in the frequency range from 1 MHz to 5 GHz.

An instrument is described with which the relative permittivity and loss of disc samples of dielectric materials may be measured over the frequency range 100?300 Mc/s. The measuring cavity is essentially a short-circuited coaxial transmission line, terminated by the sample capacitance. The line length is adjustable, so that each sample may be measured at a number of different frequencies. All measurements are based upon audio-frequency calibrations of the measuring capacitors, and the design allows these to be used with only small corrections at 300 Mc/s. The corrections are analysed, and a comparison is made of different methods used for the excitation of measuring cavities. The accuracy is estimated to be ±1% in relative permittivity, and ±1?% ±0.00002 in tan ?.