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A design for manufacturing (DFM) of a well‐performing wideband coaxial filter line using direct metal laser sintering (DMLS) additive manufacturing is proposed. The demonstrated transmission line is an air‐filled coaxial line chosen for low loss and consistent group delay over the bandwidth. Transmission line theory is used first to account for the impact of the shorted stub needed to support the central conductor. Deviations due to parasitics are described to transition the design from an ideal model to a physical prototype. The constraints inherent in DMLS are discussed and accounted for throughout the DFM. This process is demonstrated with a prototype having return and insertion losses of greater than 10 dB and less than 1.64 dB, respectively, over a 5.3:1 bandwidth from 6.4 to 33.9 GHz with a flat group delay of 129 ps ± 7%. [ABSTRACT FROM AUTHOR]

Current physics is considered to be based on Newtonian mechanics. The existence of electromagnetic waves was demonstrated by the Maxwell equations. It is also possible to assume that the constitution of electromagnetic waves forms the fundamental principles of physics, including the composition of materials. To demonstrate this assumption, we introduced electromagnetic waves in coaxial cables and determined the propagation constant of these waves, as reported in this Session. The result showed that the real part of the propagation constant, known as the attenuation constant, can be set to zero. In this case, by expressing the variable of the electromagnetic waves as angular frequency («), it is possible to treat the variable of the function as an angle (in radians). As a consequence, we are able to introduce a mathematical representation of phase (neighborhood and metric) for electromagnetic waves. Thus, we demonstrate that the mathematical representation of electromagnetic waves is possible. [ABSTRACT FROM AUTHOR]

The empirical frequency variations of the complex dielectric permittivity of Rimamid 200, Ultem PEI 1000 and Rexolite 1422 polymer materials in the range from 0.1 to 32 GHz are presented. The feasibility of employing Rimamid 200 as a microwave material is confirmed by examining S-parameters of the in-series PK2-18-01R-01R and PK2-50-05R-05R-05R coaxial adapters having identical beads fabricated from Ultem PEI 1000 and Rimamid 200. A reflection coefficient of smaller than –24 dB and a loss factor of lower than –0.16 dB in the frequency range of 0.01–50 GHz are achieved using the adapters with Rimamid 200 beads. It is noted that Rimamide 200 is a promising material for manufacturing dielectric beads and other elements of microwave equipment. [ABSTRACT FROM AUTHOR]

Heaviside reformulated the Maxwell equations because he considered that electromagnetic fields and waves have duality. As a result of the reformulation, the Poynting vector was obtained. When the variations of an electromagnetic field propagate in space as waves, this wave is referred to as an electromagnetic wave. The Poynting vector represents the traveling direction of the electromagnetic wave. In this Session, we reexamine electromagnetic fields and waves by focusing on the relationship between the Poynting vector and the duality. According to Wikipedia, no current flows in a vacuum because there are no electrons or electric charges. However, this seems to be incorrect, and the current I(x) given by rotH = I(x) flows in a vacuum. Moreover, a voltage V(x) given by rotE = -V(x) is generated because the magnetic field is the dual of the electric field and the current is the dual of the voltage. As a result, the presence of a coil in a vacuum is expressed by rotE = -V (x) = -∂B I ∂t = - pLI (x). Namely, the Maxwell equations indicate that "self-induction can occur everywhere in the atmosphere", as described by Heaviside in the book written by Nahin. Moreover, a capacitor in the atmosphere, including a vacuum, is also given by an equation because it is the dual of the coil. Thus, electromagnetic waves have physical properties of circuit elements including coils and capacitors, which are different from those of lines of forces, such as lines of electric and magnetic forces. The physics of electromagnetic waves is included in classical physics but is different from Newtonian mechanics and uses complex numbers. [ABSTRACT FROM AUTHOR]

Purpose: Experimental results and numerical simulations are presented, concerning effects of microwave generation in coaxial transmission lines which are fed with unipolar, high voltage electric pulses. The work is aimed at clarifying the relative importance of several mechanisms that could be responsible for the appearance of microwave-frequency oscillations in the course of pulse propagation through the guiding structure. Design/methodology/approach: Dispersive and filtering properties of coaxial waveguides that involve three structural sections are discussed. These latter follow one another along the axis of symmetry. Two identical sections at the input and output are filled with an isotropic liquid dielectric, while the middle part may, in addition, be either partially or fully filled with a non-conductive gyrotropic material. The inserted core represents a set of ferrite rings showing a nonlinear response to the initial high voltage, pulsed excitation. Throughout the series of measurements, the diameters of the inner conductor and of the ferrite core were kept constant. The outer conductor’s diameter was varied to permit analysis of the effect of that size proper and of the degree to which the cross-section is fi lled with ferrite. The gyrotropic properties of the ferrimagnetic material were realized through application of a magnetic bias field from an external coil. The measurements were made for a variety of pulsed voltage magnitudes from the range of hundreds of kilovolts, and magnetic bias fields of tens kiloamperes per meter. Findings: As observed in our experiments, as well as in papers by other writers, a unipolar pulse coming from the radially uniform front-end section, further on gives rise to quasi-monochromatic voltage oscillations. These appear as soon as the pulse has advanced a sufficient distance into the radially nonuniform portion of the guide. The oscillations may consist of a small number of quasi-periods, which suggests a large spectral line width. However, by properly selecting geometric parameters of the wave guiding line and the characteristics of the initial pulsed waveform it proves possible to obtain output frequencies of about units of gigahertz and pulse powers at subgigawatt levels. Conclusions: The frequencies and amplitudes of the appearing oscillations, as well as their spectral widths, are governed by the complex of dispersive and non-linear properties of the guiding structure. The diameters of the inner and outer coaxial conductors in the line, diameter of the ferrimagnetic insert and its intrinsic linear dispersion determine the set of waveguide modes capable of propagating through the line. An oscillating part of the waveform may appear and get separated from the main body of the pulse if it has originated at a higher frequency than the cut-off value for a different mode than the initial TEM.

• New apparatus: a large coaxial cell with a flow through system for high frequency broadband dielectric spectroscopy. • Calibration based on a single measurement made on reference liquid (deionized water) • Computation of complex permittivity performed based on iterative solver or optimization method using a frequency dependent model of the complex permittivity. • High performance obtained for the determination of the real part of the complex permittivity and good performance for the determination of the imaginary part of the complex permittivity. This paper presents a new apparatus: a large flow through coaxial cell designed for broadband dielectric characterization of material under controlled hydraulic and chemical boundaries. The cell is calibrated with a single measurement made on a perfectly known dielectric liquid (deionized water) together with an optimization procedure. Then, two methods are proposed to compute the dielectric characteristics: an iterative solver and an optimization method. These two methods are systematically investigated for two reference liquids: a low loss dielectric material (ethylene glycol) and high loss dielectric liquid (saline solutions with different concentration). Tabulated data were used to perform a quantitative error analysis in terms of estimated complex permittivity. The results have shown high performance in terms of real part and good performance in terms of real part. The measurements on saline solution also highlight the impact of electrode polarization with dramatic effect in the lower part of the frequency range. [ABSTRACT FROM AUTHOR]

In this session, we explain that Heaviside reformulated the Maxwell equations and showed by the vector analysis method that the direction of a flow of power of electromagnetic waves is given by the Poynting vector. Therefore, it was shown that the direction of the flow is perpendicular to the electric and magnetic flux lines. Namely, the direction of the interaction of electromagnetic waves is different from and perpendicular to the directions of the flux lines. Therefore, we examine the arrangement of the electric and magnetic fields of electromagnetic waves. As a result, it is shown that the arrangement of the electric and magnetic fields that form in coaxial transmission lines is highly effective for the transfer and work of electromagnetic waves. [ABSTRACT FROM AUTHOR]

• Scattering matrix measurements on coaxial transmission line, filled with test material. • Algorithm to estimate reflection loss for test material from scattering matrix measurements. • Test material: Ash by-products from Steel Plants – presently dumped in land fills, research on utilizing these ashes as conductive filler for microwave absorber applications. • Targeted Domain: Cement based Microwave Absorber for Low-cost large area absorber deployment. Cement based EM smart structures. • Large area absorber: Required for EMI shielding at structural level for critical infrastructure including data servers from intentional EMI and non-intentional EMI. Coaxial transmission line technique to determine Plane Wave Reflection Loss of dielectric powders is proposed. The technique provides rapid determination of suitability of powders as conductive filler for Microwave Absorbers, specifically cement based Absorber. Ash by-product from steel industry including Argon Oxygen Decarburization (AOD), Acid Recovery Station (ARS) and Electric Arc Furnace (EAF) are considered over frequency range 1–12 GHz. Scattering parameters (S-matrix) of ash filled coaxial lines are measured. Short-Open technique is adopted. Formulation to compute reflection loss from measured S 11 is presented. Teflon, with known reflection loss, is considered for validation. A 10 % error in computed results is observed in range 1–4 GHz, and 10–15 % in range 4–12 GHz. Broadband MAM characterization employing Free Space Methods involve enormous material requirement, frequency dependent prototype dimensions and anechoic chambers. The error percentage notwithstanding, the technique provides rapid estimates, enabling smart selection of conductive fillers, providing cost and time reduction. [ABSTRACT FROM AUTHOR]

The following study investigates the use of a coaxial transmission line for determining the properties of powdery dielectric materials (1–10 GHz). Four powdery materials with dielectric constants ranging from 3.5 to 70 (SiO2, Al2O3, CeO2, and TiO2) were experimentally investigated at varying volume loading fractions. Powder particles were mixed with a paraffin matrix and properties of the powder were analysed using ten mixing equations to verify their accuracy. These powder‐paraffin composites were also modelled 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 applications for new devices that utilised powder‐based dielectric materials. [ABSTRACT FROM AUTHOR]

Using CST Particle Studio, we simulate the evolution of the multipactor, beginning with a single seed electron inside a coaxial waveguide. Upon impact with either the outer or inner metallic wall, the primary electron is removed and the emitted secondary electrons are allowed to have a realistic 3-D velocity distribution. It is found that the single electron evolves very quickly into an axisymmetric distribution. The radial distribution of the multipactoring electrons is broad and very different from the infinitesimally thin multipactor electron sheet that was often assumed in previous models. The simulated threshold voltage for the onset of multipactor was compared with published experiments, and the level of agreement was found to depend on the secondary electron yield model chosen. [ABSTRACT FROM AUTHOR]

• Water is the worst contaminant that affects engine operation. • We illustrate the design of a microwave sensor for detecting water contamination. • Sensor is based on a coaxial transmission line. • Microwave attenuation changes with a sensitivity of 0.6 mdB/ppm at 6 GHz. In this paper the modeling and the design of a microwave sensor is proposed for real-time fuel quality monitoring, with particular regard to water-in-fuel measurement. A mechanical and fluid-dynamic design has been performed, evaluating the stiffness, the robustness of the sensor structure and the pressure field acting on it. Furthermore, an electromagnetic study has been carried out to verify the validity of the physical measurement principle. The adopted procedure involves the modeling of the sensor in CAD and the simulation of its behavior. The sensor, based on microwave transmittance, is attractive because of its simplicity and foreseeable low cost. [ABSTRACT FROM AUTHOR]

This work presents the results of our studies on the electromagnetic interference shielding effectiveness of small-in-size samples of ferrite composition microwave absorber prepared by using the ceramic method. The shielding effectiveness measurement was performed using the complex intrinsic parameters of the material. The coaxial holder method with the well-known test technique based on transmission/reflection measurements was used in the experimental setup. Complex intrinsic parameters were measured in the frequency range of 2-18 GHz by using the Nicholson-Ross- Weir (NRW) method with an automated test setup. First, the shielding effectiveness was measured by conventional test method and then it was calculated using complex intrinsic parameters with the NRW method. Comparison was made between measured and calculated SEs. By using a new method the SE was determined as a function of the complex intrinsic parameters of materials ϵ , μ, and frequency. This method is preferred in order to provide higher accuracy in determining material electromagnetic shielding effectiveness for small-in-size materials. For the first time, the shielding effectiveness of small-sized samples has been measured in the frequency range between 2 and 18 GHz by using the NRW method. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel approach to broadband model relative effective complex permittivity of soils (augmented broadband complex dielectric mixture model). The approach involves a combination of mixture equation and relaxation model. The mixture equation is an extension in frequency domain developed from a volume average approach. The relaxation model aims at integrating polarization effects that would occur over the frequency range under interest. In this framework, the relative effective complex permittivity is computed from a set of parameters including water saturation, porosity, cementation exponent, and relaxation parameters. The proposed model was tested and validated on a new set of data measured over the 1-MHz–3-GHz frequency range on compacted kaolin. The model was fit to the measured spectra with satisfactory agreement in terms of root-square-mean error. Furthermore, the comparison between estimated and experimentally measured water saturation and porosity has shown a good correlation. This indicates the great potential of this new model for monitoring state parameters for applications in geophysics and geotechnics. [ABSTRACT FROM AUTHOR]

We have developed multiple inductively coupled plasma (ICP) sources for large-area processes. These multiple ICP sources are composed of 16 -small ICP sources in parallel. Simulations were performed to design multiple ICP sources that could generate uniform plasma by adjusting the lengths of the coaxial transmission line and the ground-return paths. Plasma distribution was measured with an array of ion saturation probes. We demonstrated that it is possible to generate uniform plasma when equal power is supplied to each source by equalizing the lengths of the coaxial transmission line as well as maintaining the same length for all the ground-return paths. To distribute equal power to each source, the impedance of the ground path is crucial because the total impedance of a small ICP source is strongly dependent on the distance between the power supply and the source. We confirmed that this approach enables multiple ICP sources to generate uniform plasma without the need for additional control equipment. [ABSTRACT FROM AUTHOR]

A generator of high-power high-voltage nanosecond pulses is intended for electrical discharge disintegration of mineral quartz and other nonconducting minerals. It includes a 320 kV Marx pulsed voltage generator, a high-voltage glycerin-insulated coaxial peaking capacitor, and an output gas spark switch followed by a load, an electric discharge disintegration chamber. The main parameters of the generator are as follows: a voltage pulse amplitude of up to 300 kV, an output impedance of ≈10 Ω, a discharge current amplitude of up to 25 kA for a half-period of 80-90 ns, and a pulse repetition rate of up to 16 Hz. [ABSTRACT FROM AUTHOR]

This paper proposes an air-gap applied adiabatic line for a coaxial transmission line. The adiabatic characteristics with excellent microwave transmission were simulated in terms of the S-parameter and the heat transfer of coaxial lines with a finite-element-method-based tool for the adiabatic microwave design. The detailed design scheme of the air-gap adiabatic line is presented and its performance is evaluated. The adiabatic efficiency associated with microwave feature was analyzed by a resistive equivalent circuit model of the line. We made a stainless steel air-gap adiabatic line that had about 11 times greater thermal resistance than that of a gapless coaxial line, a beryllium copper line, with the increment of just 0.4-dB insertion loss. We also propose a solution to improve the low-frequency transmission of an air-gap adiabatic line with a tunable ground wire for broad-band feature. [ABSTRACT FROM PUBLISHER]

In this paper, it is found that the coaxial transmission line between the matching box and the plasma reactor plays an important role in impedance matching of atmospheric-pressure radio-frequency capacitively coupled microplasma discharge characterized by very low capacitance value. The high output voltage across reactor terminal is generated when the external circuit is operating in resonant state driven by power supply. The experimental results show that coaxial transmission line exhibits capacitive characteristics within the working frequency range and its capacitance increases linearly with the length of the transmission lines; the resonant frequency and voltage across the terminal reactor decrease with the length of coaxial transmission line. [ABSTRACT FROM AUTHOR]

This paper describes the design process of a fast pulse generator, based on a transmission line (TL) system and a spark gap, including its experimental validation. Design criteria and expected parameters are described. Simulation results for the pulse generator obtained with a TL model are presented. This model is implemented using the software package Electromagnetic Transient Program—Alternative Transient program (EMTP-ATP). A constructed pulse generator [based on the mentioned design as well as the simulation results using EMTP-ATP and finite-element method (FEM)] is presented and laboratory test results are described. Simulations and experimental results fit well, except for a difference of 15% in the rise time. The proposed design procedure, which combines TL simulations, theoretical models, and FEM simulations, has been experimentally validated and it can be used to design pulse generator systems for different applications. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the electromagnetic shielding effectiveness (EMSE) of thin and lightweight knitted fabrics that are suitable for casual wear like t-shirts. For the purpose of having a low production cost, metal/cotton conductive composite yarns are produced by a yarn doubling technique, involving stainless steel wires (35 μm, 50 μm) or copper wires (50 μm, 70 μm) and Ne30/1, Ne40/1, Ne60/2, Ne80/2 count cotton yarns. Single jersey fabrics are knitted on an E20 circular knitting machine with the same machine settings. Coaxial transmission line and free space measurement (by using an anechoic chamber) techniques are used for the EMSE measurements in the frequency range of 100 MHz–1.5 GHz and 1 GHz–18 GHz respectively. The free space measurement technique test results reveal that single jersey knitted fabrics have EMSE ability for the electric field polarization in the same direction as the main direction of the conductive metal wires in the fabric. It is observed that all single jersey fabric structures have more than 7 dB (80% or better) EMSE for GSM-850 and GSM-900 cellular phone communication bands according to coaxial transmission line equipment test results. SNK test results of both test methods reveal that, while 100% cotton fabrics do not have EMSE ability, cotton yarn count is highly significant on the EMSE of single jersey fabrics with conductive composite yarns. Fabrics with two-ply fine cotton yarns (Ne60/2 and Ne80/2) have higher EMSE values than the fabrics with one-ply cotton yarn of the same yarn count (Ne30/1 and Ne40/1). [ABSTRACT FROM PUBLISHER]

This article is a study of an empirical design of an open-ended coaxial cavity resonator. The coaxial cavity resonator can be designed using the coaxial transmission-line theory. It can be done by using the radius of the inner conductor, the inner radius, and the length of the resonator. However, the basic coaxial transmission-line theory can be seen that the characteristics of the resonant frequency and the Q value are varied by the change of length, regardless of the value of radius of the inner conductor and inner radius of the resonator. We find out the impact of radius of the inner conductor, inner radius of the resonator, and the length of the resonator parameter and propose the optimized empirical resonator design method by reducing the error between the theoretical value and the design value. High frequency structure simulator was used for simulation and the material of the resonator was designed with a copper. Based on the simulation, several resonators are fabricated by the size of 14 mm for the radius of inner conductor, 2, 5, and 10 mm, respectively, for the inner radius of resonator, and 8.5 mm for the length of the resonator. The resonant frequencies of the produced resonators were measured at 6.1, 5.7, and 6.5 GHz, respectively. According to the result of simulation and measurement, we know that we can design the relatively exact open-ended coaxial cavity resonator by applying the basic coaxial transmission-line theory directly when the length of the resonator is less than 10 mm, and adding the correction factor of 0.5 GHz to the calculated resonant frequency in case of more than 10 mm of the length of the resonator. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:606-610, 2014 [ABSTRACT FROM AUTHOR]

A molecule dynamics model and details of a large electrical volume coaxial spectrometer are presented in this paper. The molecule dynamics model gives successful molecular signal decay predictions in coaxial spectrometers and shows that our current design is beyond the wall collision limit. The dimensions of the large electrical volume coax and a solution for practical fabrication of the transmission line that avoids spurious mode coupling are also introduced in this paper. The measured spectrum has an 8-dB improvement in signal-to-noise ratio over previous techniques, and fast detection was achieved with 100 averages. The better performance of this coaxial transmission line spectrometer improves its potential in the application of microwave chemical sensing, and the molecule dynamics model is useful for future coaxial spectrometer designs for higher operation frequency where molecular signals are stronger. [ABSTRACT FROM AUTHOR]

Abstract: The use of a capacitive probe as a non-destructive investigative technique for controlling the post tensioned ducts of bridges has gained increasing acceptance in France since several years. A field campaign measurement made in 2006 has shown the performance of the capacitive probe developed by the IFSTTAR. Nevertheless, some results are not understood, and in particular the behaviour of the probe when cement exudation product are present in the duct. Without an accurate knowledge of the electromagnetic properties of those products it is impossible to quantitatively assess the results of our capacitive probe. This paper reports the development of a coaxial transmission line feature. It was designed to allow the evaluation of a large type of material (liquid, paste or granular) over a large frequency range (50MHz–4GHz at maximum). A calibration scheme developed before at the Fresnel Institute was used. Using a two port S parameter instrument, the complex permittivity and magnetic permeability were evaluated by frequency domain measurement. The electromagnetic characterization of cement paste, cement exudation products and injection wax has brought us some key results in the interpretation of the capacitive probe signal. The results of this characterization were then used in a 3D semi analytical modelling of the problem. The studies of configurations with exudation products are presented and compared to experimental results obtained with our capacitive probe on laboratory duct. [Copyright &y& Elsevier]

We present the measurements performed with a custom coaxial-cage line designed to determine the complex dielectric permittivity of large samples, made of granular and/or liquid materials. The open structure of the cage facilitates the filling of the line, and allows the uniform compactness of the granular materials having large grain size. The electromagnetic parameters of the samples are retrieved using the line scattering coefficients (S-parameters), measured with a vector network analyzer in the frequency range 1 MHz to 3 GHz. The measurements are carried out on water, ethanol, and glass beads using the Boughriet method, which, for non magnetic materials, optimizes the Nicolson–Ross–Weir algorithm. The results confirm that such a device accurately estimates the material complex permittivity in a wide frequency band. However, at very low frequencies and at frequencies multiple of the line half-wavelength resonances, the accuracy significantly reduces. In particular, the accuracy gets worse for materials with high permittivity and low losses. Nevertheless, for natural geo-materials, usually characterized by appreciable losses, the coaxial-cage line can effectively be used to accurately estimate the material electromagnetic properties in a wide frequency band. [ABSTRACT FROM PUBLISHER]

Abstract: There is magnetic force acting on the wall of a square coaxial transmission line when TEM wave propagates in it. The self-inductance can be determined based on a conformal transformation for the field region, which demonstrates that the inductance only depends on the side length ratio of the two walls instead of the length of the walls. The magnetic force on each side of the walls is then calculated by employing the principle of virtual work. It is proved that the magnetic force has the same magnitude and opposite direction to the electric force. And then the electromagnetic force on the wall is zero. The general meaning of this conclusion for all kinds of coaxial transmission line is proposed. [Copyright &y& Elsevier]

In this article, we present a study dealing with the design, optimization, and manufacturing of different versions of a broadband monopole antenna with a convex conical reflector. These antennas are created by a wire monopole that is placed into the axis of a convex conical reflector. The principle of antennas is based on the transformation of the impedance of a coaxial transmission line to the open space impedance via a circular waveguide. The results of simulations performed in CST Microwave Studio are mutually compared. Then, the simulated versions of broadband monopole antennas were optimized with respect to specified objectives. According the available materials, we built selected versions of the antenna and experimentally verified their properties. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1243-1247, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27598 [ABSTRACT FROM AUTHOR]

Abstract: 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 10MHz to 1.5GHz 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 10MHz, 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 0.515g/cm3 to 3.08 at 0.875g/cm3. 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. [Copyright &y& Elsevier]

Abstract: Microwave magnetic performance of thin ferromagnetic films is of interest in view of many technical problems. For measuring the microwave permeability, a shorted stripline technique is in common use. Recently, a coaxial technique has been developed for permeability measurements of films deposited onto a flexible substrate. The coaxial technique is reported to be advantageous over the conventional stripline method in wideband operating range and accuracy. In this paper, measurement results are presented which are obtained with these two techniques for Fe–N films. It is found that the magnetoelastic effect contributes greatly to the measured microwave permeability of the films. With the coaxial measurements under an external magnetic bias, this effect may be accounted for to estimate the permeability of a plane film sample. Additional information on the properties of the film can also be extracted from these data, such as estimations of average magnetic anisotropy field and of the magnetostriction constant of the film. [Copyright &y& Elsevier]

Abstract: At radio-frequencies, measurements of the permittivity of ice are sparse and with unknown or large uncertainty. Coaxial transmission lines have been established for frequency-dependent permittivity determination for a broad variety of materials. Here we present a coaxial transmission line setup originally designed for soil samples, now adapted for measuring ice samples between 10MHz and 1.5GHz. Measured scattering parameters are assessed for artifacts against a forward calculation based on transmission line theory. A Debye-type relaxation function for the complex permittivity is assumed to obtain the permittivity of ice from the measured full set of four scattering parameters by means of a genetic optimization algorithm. The algorithm is successfully validated against quasi-analytical and iterative computation techniques with reference measurements of a low-loss Teflon standard. Based on the forward calculation and the Teflon standard, the total uncertainty for measuring the real part of the permittivity is estimated to be around 1%. Additional measurements of reference materials air, water, ethanol and methanol are used for validation. The real part of the permittivity of eight artificial pure ice samples is found frequency-independent between 10MHz and 1.5GHz at −20°C, with a mean value of 3.18±0.01. [Copyright &y& Elsevier]

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 [ABSTRACT FROM AUTHOR]

Abstract: The occasion of the electromagnetic interference (EMI) is essentially electrical, with unwanted electromagnetic emission being either radiated or conducted. The main goal of this investigation is to develop conductive textile composites with desirable properties of electromagnetic shielding effectiveness (EMSE). The shielding effectiveness properties of the conductive fabrics reinforced thermoplastic composites were investigate in this study. The copper wire and stainless steel wire were wrapping with polyamide filaments to reduce the friction and tenacity during weaving and knitting process, enabling the successful weaving and knitting of hybrid conductive yarn, RTCY namely. The co-woven-knitted fabric and woven fabric were fabricated with RTCY to reach desired electromagnetic shielding properties. The shielding effectiveness of different textile processes and materials are also investigated with various measurement techniques. This investigation tried to evaluate the shielding effectiveness via various measurement techniques and test standards. This investigation carried out with three kind of different coaxial transmission line testing chambers for ASTM 4935, ASTM ES7 and self-constructed one. The various chambers have different wave processing modes on testing. The shielding effectiveness was measured with different test method and test standard to compare the differences between various measurement systems and try to express the contrast between different wave processing modes on testing. [Copyright &y& Elsevier]

Abstract: During the fabricating of extended-PTFE (ePTFE) fabrics, we found that the ePTFE yarn is easy to be collapsed because of excluding each other by electrostatic friction of the ePTFE yarn during warping procedure. Therefore, the single warping was adopted in the experiment and we also added some anti-electrostatic solution and enhanced the humidity of warping to decrease the influence. During weaving process, the small fell of cloth (32mm) was carried out and the warp level angle (312°) was advanced to prevent the crinkle of fabric caused by shrunk weft yarn. In the investigation of the physical properties of ePTFE fabric, we found that both of the acid-resistance and heat-resistance are really excellent. Even if the ePTFE fabric is used in the environment temperature of 300°C for 1h, there is still no change in the mechanical properties. Heat shrinkage has rarely different at temperature of 100 and 200°C, but it changed obviously at the temperature of 300°C. In this study, when the fabric structure was 3/1 right twill and the weft density was 20picks/cm, it will have the optimum breaking strength. [Copyright &y& Elsevier]

Air-filled copper Ka-band resonators with heights between 250–700 μm are demonstrated with measured un-loaded Q factors between 440–829. The low-profile quasi-planar resonators are fabricated using a sequential metal deposition process. Miniaturization of up to 70% with respect to a TE101 quasi-planar resonator is accomplished by reducing the footprint of the resonator while maintaining the height. Finite-element simulations predict the measured resonant frequency within less than 1%. Due to fabrication imperfections, Qun is measured to be approximately 15% less than predicted. The resonators are compatible with air-filled rectangular microcoaxial feed lines fabricated in the same metal-deposition process. [ABSTRACT FROM AUTHOR]

Several low-profile 250-mum-high Ka-band cavity resonators are demonstrated with resonant frequencies near 26 GHz and unloaded quality (Q) factors greater than 400. The air-filled copper cavity resonators are fabricated on a silicon substrate using a photolithographic process. A microrectangular coaxial transmission-line feed is integrated in the same process. Four resonators with different mechanical support structures are demonstrated. The resonators are designed using the finite-element method and simulation of both the resonant frequency and Q factor agree well with measurements [ABSTRACT FROM PUBLISHER]

In this paper, we present a tool for permittivity re-construction. The tool consists of a coaxial transmission line and a novel analytical reconstruction technique. The line is designed for accurate permittivity measurements of soil samples. It allows for single or double phase flow. The full S-parameter matrix is modeled with transmission line theory. We show that for accurate measurements each component of the tool needs careful calibration. We give a method to compute the sensitivity of these measurements to different materials, and we show the accuracy in the determination of the sample permittivity from the measurements based on deviations of the forward model compared to measured results as a function of the error in the sample permittivity. We demonstrate that a maximum error of less than 1% is obtained for the possible permittivity reconstruction from these measurements for wavelengths less than five times the sample holder length. The novel reconstruction technique is based in the propagation matrices method. It consists in rewriting the transmission line model in matrix notation and relating the S-parameters to the total reflection and transmission of the line seen as a two-port network. Thanks to this novel approach, the reconstruction of both permittivity and permeability can be done directly from the measured S-parameters of the line. Due to experimental instabilities the errors are considerable, and we must restrict ourselves to the reconstruction of permittivity. Results on an air sample are within the predicted error of 1%. Computing relative errors for an ethanol sample is not possible due to temperature and purity difference between our experiment and published results; nevertheless, the reconstructed permittivity of ethanol follows the Debye model. [ABSTRACT FROM AUTHOR]

The main goal of this letter is the analysis of the multipactor effect within a coaxial waveguide structure when an external axial dc magnetic field is applied. We have designed and manufactured a coaxial waveguide sample that has been immersed within a long solenoid. Numerical and experimental results confirm a significant change in the RF breakdown behavior with regard to the case without the axial dc magnetic field, as well as the existence of single- and double-surface multipactor regimes. Good agreement between theory and experimental data has been found. [ABSTRACT FROM PUBLISHER]

In this article, we propose a new method to measure the complex relative permittivity (ℇr = ℇr′ - jℇr″) and permeability (μr = μr′ - jμr″) of liquid- or powder-type materials using a two-port probe which is constructed from coaxial transmission lines. The two-port probe is a simple structure that can be easily fabricated with low cost in comparison with conventional probes which are the type of the cavity and waveguide. And we have adopted the Cole–Cole equation and air-filled coaxial cable for calibrating the proposed probe. To verify the performance of the proposed probe, we measured the properties of materials in the form of liquids and powders and compared the results with those measured by the air-filled coaxial cable, which shows good agreement. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2977–2979, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24793 [ABSTRACT FROM AUTHOR]

Background: It is technically challenging to design compact yet sensitive miniature catheter radio frequency (RF) coils for endovascular interventional MR imaging., Methods: In this work, a new design method for catheter RF coils is proposed based on the coaxial transmission line resonator (TLR) technique. Due to its distributed circuit, the TLR catheter coil does not need any lumped capacitors to support its resonance, which simplifies the practical design and construction and provides a straightforward technique for designing miniature catheter-mounted imaging coils that are appropriate for interventional neurovascular procedures. The outer conductor of the TLR serves as an RF shield, which prevents electromagnetic energy loss, and improves coil Q factors. It also minimizes interaction with surrounding tissues and signal losses along the catheter coil. To investigate the technique, a prototype catheter coil was built using the proposed coaxial TLR technique and evaluated with standard RF testing and measurement methods and MR imaging experiments. Numerical simulation was carried out to assess the RF electromagnetic field behavior of the proposed TLR catheter coil and the conventional lumped-element catheter coil., Results: The proposed TLR catheter coil was successfully tuned to 64 MHz for proton imaging at 1.5 T. B 1 fields were numerically calculated, showing improved magnetic field intensity of the TLR catheter coil over the conventional lumped-element catheter coil. MR images were acquired from a dedicated vascular phantom using the TLR catheter coil and also the system body coil. The TLR catheter coil is able to provide a significant signal-to-noise ratio (SNR) increase (a factor of 200 to 300) over its imaging volume relative to the body coil., Conclusions: Catheter imaging RF coil design using the proposed coaxial TLR technique is feasible and advantageous in endovascular interventional MR imaging applications., Competing Interests: Conflicts of Interest: The authors have no conflicts of interest to declare.