Electromagnetic Characterization Research Articles

Responses to comments on assessment of polarization dependence of body shadow effect on dosimetry measurements in the 2.4 GHz band.

Sub-Directorate-General for Research Assessment and Promotion (Carlos III Health Institute) for the project “Electromagnetic Characterization in Smart Environments of Healthcare, and their involvement in Personal, Occupational, and Environmental Health”; grant number: DGPY-1285/15 (PI14CIII/ 00056); Human resources of the project “Assessment of Exposure to NonIonizing Radiation from Wireless Communication Technologies and its Relation to the Health of Humans”; grant number: DGPY-1064/13 (CA12/00038)

Electromagnetic analysis of a superconducting transformer for high current characterization of cable in conduit conductors in background magnetic field

A large cable-in-conduit-conductor (CICC) test facility has been designed and fabricated at the High Magnetic Field Laboratory of the Chinese Academy of Sciences (CHMFL) in order to meet the test requirement of the conductors which are applied to the future fusion reactor. The critical component of the test facility is an 80kA superconducting transformer which consists of a multi-turn primary coil and a minor-turn secondary coil. As the current source of the conductor samples, the electromagnetic performance of the superconducting transformer determines the stability and safety of the test facility. In this paper, the key factors and parameters, which have much impact on the performance of the transformer, are analyzed in detail. The conceptual design and optimizing principles of the transformer are discussed. An Electromagnetic-Circuit coupled model built in ANSYS Multiphysics is successfully used to investigate the electromagnetic characterization of the transformer under the dynamic operation condition.

Influence of the aspect ratio of magnetic metallic additives on the microwave absorbing performance

This work aims to show the behavior of radar absorbing materials (RAM) based on magnetic metallic additives with different aspect ratios. For this, two materials, carbonyl iron, constituted of spherical iron particles, and carbon-steel filaments were used. These additives were characterized considering their morphological and structural features. X-ray diffraction analysis shows that the two additives have the same crystallographic structure, but their morphologies are quite different in micrometer scale. Epoxy resin/metallic additive composites using the neat additives and their mixtures were prepared. The electromagnetic characterization of the composites evaluated the permittivity, permeability and reflectivity behaviors in the frequency range of 8.2–12.4 GHz. The results show that the samples obtained with the mixture of the two additives resulted in composites with high complex parameters of permittivity and permeability. Better RAM performance is observed for samples based on metallic filaments and for more concentrated mixtures containing the two additives (values up to −14 dB or ~96% of attenuation). The influence of specimen-thickness on the RAM performance is also observed.

A wideband terahertz high-Tc superconducting Josephson-junction mixer: electromagnetic design, analysis and characterization

This paper presents a wideband terahertz (THz) mixer based on a thin-film antenna-coupled high-temperature superconducting (HTS) YBa2Cu3O7−x (YBCO) step-edge Josephson junction. The HTS mixer enables the flexible harmonic mixing operation at multiple THz bands with the same microwave local oscillator (LO) source, and features very wide intermediate-frequency or instantaneous bandwidth. In order to optimize the frequency down-conversion performance of the mixer, systematic electromagnetic design and analysis have been carried out to improve the power coupling of THz radiation as well as wideband transmission of microwave signals. Experimental characterization of a fabricated device prototype has demonstrated that the mixer exhibits good performance at both the 200 GHz and 600 GHz bands. Detailed measurement results including the DC characteristics, LO pumping requirement, frequency response, mixing linearity and conversion gain are presented in this paper.

Characterization of resonant impedances of CERN-SPS gate valves

For the CERN High Luminosity LHC project, a doubling of bunch intensity is foreseen. However, this intensity increase is currently limited by the LHC injector chain, in part due to longitudinal multi-bunch instabilities in the SPS. Therefore, the implementation of an accurate SPS impedance model was started some time ago in order to obtain a better understanding of instability sources and develop mitigation measures. In this paper, we present the electromagnetic characterization of commonly used all-metal gate valves with respect to their contribution to the SPS longitudinal impedance. The valve impedance was evaluated with commercially available EM-field simulation programs and verified with RF-bench measurements. Using this input, it was possible to obtain in particle simulations the dependence of the multibunch stability threshold on the number of these valves. The threshold can be increased by using commercially available impedance shielded valves. Consequently, we present the associated reduction in beam coupling impedance and the expected gain in beam stability if all existing unshielded valves are replaced by shielded ones.

Structural and electromagnetic characterization of Co-Mn doped Ni-Sn ferrites fabricated via micro-emulsion route

Ni0.5Sn0.5CoxMnxFe2−2xO4 ferrites with x=0.0–0.8 have been prepared by the micro-emulsion method, using CTAB as a surfactant material. X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR) and vibrational sample magnetometer (VSM) were used to investigate the effects of Co and Mn substitutions on cationic distribution, crystallite size, lattice constant, spectral, magnetic and dielectric properties. Lattice constant and crystallite size were found to increase from 7.4 to 9.25Å and from 11.8 to 19.7nm respectively with increasing substitution of Co and Mn ions. Saturation magnetization (MS) gradually increased from 20.5 to 47.6emu/g with increase in the value of x. However, Coercivity increased from 152.7 to 462.4Oe up to x=0.4 and then it decreased thereafter. The dielectric constant, complex dielectric constant and tan loss (tanδ) were observed to decrease with increase in frequency, depicting the semiconductor behavior of the ferrites. Dc resistivity was observed to decrease considerably upon addition of Co and Mn content. The outcome for the tunable magnetic properties and achieved modification of the synthesized nanocrystallites may be chosen for tremendous applications; such as miniaturized memory devices that are based on the energy storage principles and capacitive components.

Electromagnetic Performance Estimation of UHF RFID Tags in Harsh Contexts

Radio-Frequency Identification (RFID) technology is a consolidated example of electromagnetic system in which passive labels equipped with flexible antennas, called tags, are able to use a portion of the electromagnetic energy from the reader antennas, power-up their internal circuitry and provide the automatic identification of objects. Being fully-passive, the performance of RFID tags is strongly dependent on the context, so that the selection of the most suitable tag for the specific application becomes a key point. In this work, a cost-effective but accurate system for the over-the-air electromagnetic characterization of assembled UHF RFID tags is firstly presented and then validated through comparison with a consolidated and diffused measurement systems. Moreover, challenging use-cases demonstrating the usefulness of the proposed systems in analyzing the electromagnetic performance of label-type tags also when applied on materials on different shape or embedded into concrete blocks have been carried out.

Synthesis and electromagnetic property of Li0.35Zn0.3Fe2.35O4 grafted with polyaniline fibers

Li0.35Zn0.3Fe2.35O4 (LZFO) grafted with polyaniline (PANI) fibers was synthesized by in-situ polymerization. FTIR, XRD, SEM and electromagnetic characterization were used to investigate chemical composition, micro-morphology, electromagnetic properties and microwave absorbing properties of the composite. The results show that PANI fibers were grafted on the surfaces of LZFO particles. The reflection loss exceeds 10dB in the frequency range from 2.5 to 5GHz and from 15 to 17GHz, and the maximum reflection loss reaches −33dB at 15.9GHz. The enhanced microwave absorption properties of the LZFO/PANI-fiber composites are mainly ascribed to the combined effect of the dielectric and magnetic loss and the improved impedance matching.

Electromagnetic characterization of cola drinks

The electromagnetic characterization of liquids could be of great interest to manufacturing companies, as it could provide information about the quality of beverages. They could use this knowledge to optimize production processes. Using the probe reflection system, dielectric properties of different varieties of Coca-Cola and Pepsi products in cans have been examined. Measurements have been performed at several temperatures between 0 and 60 degrees Celsius and at periods after opening of 0, 6, 24 and 48h. The applied frequency range goes from 0 to 20GHz in steps of 200Hz. Both experimental and theoretical approaches have been used to model the results. Although all varieties follow the same trend, the results clearly show that differences exist in the electromagnetic behavior of the two brands and of the different varieties.

Inhomogeneous media characterization: a hybrid method of state space and frequency diversity

This paper presents an analytical method for the reconstruction of permittivity profile of an inhomogeneous slab. The proposed method which is based on state transition matrix combines state space formulation and frequency domain data. This methodology and formulation lead to an accurate inversion of complex inhomogeneous profiles. Comparing with other analytical methods, the proposed approach avoids solving the nonlinear integro-differential equation, which consequently yields mathematical implementation. In order to validate the algorithm, some inhomogeneous profiles with different levels of complexity are considered and analyzed. The results show that the proposed method can be considered as a robust technique for one-dimensional inverse scattering problems. The results are valuable for the study and electromagnetic characterization of inhomogeneous and planar layered media.

Electromagnetic Characterization of Aircraft Composite Materials and its Effects on the Antenna Performance

This paper presents an electromagnetic characterization of aircraft composite materials, as well as numerical and experimental analyses of its effects on the antenna performance. Two uncalibrated S-parameters characterization methods have been applied for retrieving the complex electrical permittivity in the L- and C-band, namely: Air-region method and Sample-shifted method. Dielectric constants of 4.6 and 1.84 and loss tangent of 2.0x10 -2 and 6.1x10 -2 have been obtained for fiberglass and honeycomb composite materials, respectively. A 3.0-meters prototype of an Embraer light jet aircraft dorsal fin was fabricated and used in the experiments in a semi-anechoic chamber in order to evaluate the impact of installing aeronautical VHF and L-band antennas on a fuselage made of composite materials.

Electromagnetic simulation and experimental characterization of RF interaction structure of an S-band magnetically insulated line oscillator

An S-band RF interaction structure of a magnetically insulated line oscillator operating at fundamental-mode was designed using analytical formulations, and simulated using 3-D electromagnetic code CST Microwave Studio for its dispersion characteristics and RF output performance. The slow-wave structure was fabricated using precision CNC machining and characterized for its dispersion characteristics. The measured value of pi-mode frequency was found to be in close agreement (2.6%) with that from the simulation.

Electromagnetic characterization of advanced nanostructured materials and multilayer design optimization for metrological and low radar observability applications

In this work the electromagnetic characterization of composite materials reinforced with carbon and metallic nanoparticles is presented. In particular, the electric permittivity and the magnetic permeability as a function of the frequency are used to evaluate the electromagnetic absorption capability of the nanocomposites. The aim is the study of possible applications in advanced coating able to tune the electromagnetic reflectivity of satellite surfaces in specific frequency ranges, in a special way for those surfaces that for some reason could be exposed to the antenna radiation pattern. In fact, the interference caused by the spurious electromagnetic multipath due to good electric conductive satellite surface components could in turn affect the main radiation lobe of TLC and Telemetry antennas, thus modifying its main propagation directions and finally increasing the microwave channel pathloss. The work reports the analysis of different nanostructured materials in the 2–10GHz frequency range. The employed nanopowders are of carbon nanotubes, cobalt, argent, titanium, nickel, zinc, copper, iron, boron, bismuth, hafnium, in different weight percentages versus the hosting polymeric matrix. The materials are classified as a function of their electromagnetic losses capability by taking into account of both electric and magnetic properties. The possibility to design multi-layered structures optimized to provide specific microwave response is finally analyzed by the aid of swam intelligence algorithm. This novel technique is in general interesting for metrological purpose and remote sensing purposes, and can be effectively used in aerospace field for frequency selective materials design, in order to reduce the aircraft/spacecraft radar observability at certain frequencies.

Development of a multi-linear quadratic experimental design for the EM characterization of concretes in the radar frequency-band

This study is focused on the electromagnetic characterization of concretes within the ground-penetrating radar frequency band. The evaluation of the complex dielectric properties is carried out in laboratory on 36 different concrete specimens defined by a specific experimental design. The composition parameters of the concrete mix design are the aggregate nature, the aggregate content, the cement nature, the cement content and the water to cement ratio (W/C).The model of relative permittivity associated to the experimental design is a multi-linear polynomial of the 5 chosen material parameters. The exploitation of this set of data consists in a calculation level of the coefficients of this model independently for the real and the imaginary parts of the relative permittivity. This reveals the significant relationship between the dielectric properties and the composition parameters.Raw results in terms of the real and imaginary parts of the dielectric permittivity along frequencies are presented for 36 different concretes in dry and saturated conditions and the sensitivity of the parameters are discussed.

Electromagnetic characterization of nonevaporable getter properties between 220–330 and 500–750 GHz for the Compact Linear Collider damping rings

Due to its effective pumping ability, nonevaporable getter (NEG) coating is considered for the vacuum chambers of the Compact Linear Collider (CLIC) electron damping rings (EDR). The aim is to suppress fast beam ion instabilities. The electromagnetic (EM) characterization of the NEG properties up to ultra-high frequencies is required for the correct impedance modeling of the damping ring (DR) components. The properties are determined using rectangular waveguides which are coated with NEG. The method is based on a combination of complex transmission coefficient ${S}_{21}$ measurements with a vector network analyzer (VNA) and 3D simulations using CST Microwave Studio\textregistered{} (CST MWS). The frequency ranges discussed in this paper are 220--330 and 500--750 GHz.

High-performance near-field electromagnetic wave attenuation in ultra-thin and transparent graphene films

Ultra-thin and transparent electromagnetic interference (EMI) shielding and absorbing materials are in increasing demand for near-field electromagnetic wave attenuation in transparent electronic devices that get thinner and lighter. Here, we report chemical-doped and undoped graphene as the thinnest and transparent shield for high-performance near-field electromagnetic wave attenuation. The electromagnetic loss characterization demonstrate that a single layer graphene film exhibits a giant magnetic field transmission loss normalized to the film thickness that is at least two orders of magnitude higher than those of conventional EMI shielding and absorbing materials, which is attributed to the outstanding magnetic field mirroring in graphene. The doped and double-layer graphene films exhibit superior power and transmission losses than the commercial transparent indium tin oxide shield over the frequency range from 0.1 GHz to 6 GHz. The high-performance near-field electromagnetic wave attenuation in graphene enables broad range applications such as futuristic transparent display devices.

Miniaturization and Bandwidth Enhancement of a Microstrip Patch Antenna Using Magneto-Dielectric Materials for Proximity Fuze Application

The exact calculation of height of burst has always been a challenge in the design of proximity fuzes. Radio frequency-based sensors can be designed for this purpose but the size and bandwidth of the antenna increases the design complexity; hence, miniaturization of the patch antenna using barium hexaferrite (BaFe12O19) as substrate material is proposed in this paper. The nanohexaferrite substrate material was prepared using a wet chemical method and characterized for structural and electromagnetic properties. An average crystallite size of 60 nm was obtained from x-ray diffraction. Scanning electron microscopy and transmission electron microscopy also confirms the formation of homogenous nanoferrites. Complex permittivity (ɛ* = 6.2 − 0.04 j) and complex permeability (μ* = 1.9 − 0.18 j) were obtained from electromagnetic characterization. The antenna structure fabricated and simulated confirms that, with the obtained electromagnetic parameters of synthesized magneto-dielectric material, the size of antenna can be reduced up to 42.5%. It also increases the bandwidth from 68 MHz to 166 MHz with respect to antenna on FR4 substrate. Therefore, BaFe12O19 is proposed as a suitable candidate for a high-bandwidth, miniaturized antenna for proximity fuzes.

Electromagnetic, Morphological, and Electrical Characterization of POMA/Carbon Nanotubes-Based Composites

This study involves the preparation of conducting composites based on poly(o-methoxyaniline) (POMA) and carbon nanotubes (CNT) and the evaluation of them as radar absorbing materials (RAM), in the frequency range of 8.2–12.4 GHz (X-band). The composites were obtained by synthesis in situ of POMA in the presence of CNT (0.1 and 0.5 wt% in relation to the o-methoxyaniline monomer). The resulting samples—POMA/CNT-0.1 wt% and POMA/CNT-0.5 wt%—were incorporated in an epoxy resin matrix in the proportion of 1 and 10 wt%. FT-IR analyses show that the POMA was successfully synthesized on the CNT surface. SEM analyses show that the synthesized POMA recovered all CNT surface. Electrical conductivity measurements show that the CNT contributed to increase the conductivity of POMA/CNT composites (1.5–6.7 S·cm−1) in relation to the neat POMA (5.4 × 10−1 S·cm−1). The electromagnetic characterization involved the measurements of complex parameters of electrical permittivity (ε) and magnetic permeability (µ), using a waveguide in the X-band. From these experimental data reflection loss (RL) simulations were performed for specimens with different thicknesses. The complex parameters show that the CNT in the composites increased ε and µ. These results are attributed to the CNT network formation into the composites. Simulated RL curves of neat POMA and POMA/CNT in epoxy resin show the preponderant influence of POMA on all RL curves. This behavior is attributed to the efficient CNT recovering by POMA. RL results show that the composite based on 10 wt% of POMA/CNT-0.5 wt% in epoxy resin (9 mm thickness) presents the best RL results (≈87% of attenuation at 12.4 GHz).

Wideband Negative Permittivity and Double Negative Fishnet-Mushroom-Like Metamaterial in X-Band Waveguide

A Fishnet-Mushroom-like metamaterial electromagnetic behaviour is represented in S-parameters numerically and experimentally for X-band frequencies arena. The design has introduced a dielectric substrate as a host with metallic parts. The proposed design is predicted to provide the electromagnetic band gap characterization with desired reiterative characteristic parameters, negative permittivity, and negative permeability exhibiting a double negative left-handed region, which is identified with the X-band regime with good agreement between the simulated and the measured results.

Assembly-Line-Compatible Electromagnetic Characterization of Wearable Antenna Substrates

Electromagnetic characterization of materials applied in wearable components is of paramount importance for the design and production of reliable devices. Therefore, we propose a novel approach that compares simulations and measurements performed by a resonance-perturbation method. An inset-fed patch antenna operating in the vicinity of the 2.45-GHz Industrial, Scientific, and Medical frequency band enables us to quickly estimate the properties of a given substrate sample. First, the two frequency values at which the simulated return loss peak of the fixture crosses a given threshold value are modeled as polynomial functions of the material's relative permittivity and loss tangent. Then, the comparison between modeled and measured frequencies yields the electromagnetic properties of the material. The approach is validated by characterizing the high-frequency laminate on which the antenna is implemented. Next, the method is applied to several textile materials of interest. It is shown that the proposed technique is fast, precise, and nondestructive. As such, it is suitable for integration into an assembly line, where substrate samples are first quickly characterized before being used in the production of the actual antennas.