Permittivity Of Material Research Articles

A modified AMC-based antenna sensor for contactless measurement of complex permittivity

The paper proposes a modified artificial magnetic conductor (M-AMC)-based antenna sensor for retrieving the complex permittivity of material under test (MUT). The antenna sensor measurement system is composed of a coplanar waveguide (CPW) antenna and a M-AMC structure. The M-AMC structure consists of a 3×3 array, and each unit cell is fabricated by two-layer dielectric substrates. The M-AMC unit cell is evolved from the traditional square unit one, and in each cell, four bent microstrip lines are embedded in the middle plane of M-AMC structure to connect the top square metallic patch through metallic holes. Compared with traditional AMC structure, the added bent microstrip line can increase the current path. Besides, four complementary split-ring resonators (CSRRs) are etched on the top plane of each unit to improve the density of electrical field. A large metallic patch covers the bottom plane of M-AMC. The resonant frequency of M-AMC structure is reduced a lot than the traditional one, which is beneficial to realize miniaturization. In measurement, the antenna is placed on the upper surface of M-AMC structure with an appropriate distance, and the MUT is placed on top plane of M-AMC. The MUTs with different thicknesses and complex permittivity will alter the resonant frequency and quality factor of the antenna sensor. Experiment is carried out to demonstrate the performances of proposed antenna sensor. An average sensitivity of 1.89 % is achieved and the maximum error is less than 3.516 % in extracting the real permittivity. All in all, the proposed antenna sensor has a potential superiority in the scope of material characterization.

Field-Based Circuit Model of Acoustically Actuated Piezoelectric Antenna for Characteristic Evaluation and Array Applications

A field-based circuit model (FBCM) is proposed to reveal impedance, near-field, and far-field performance of acoustically actuated piezoelectric (PE) antenna by introduction of electromagnetic induction into PE equations and impedance analysis at the boundary. To make the model more practical, induced current on the PE antenna body is analyzed and near-field compression by the large permittivity of PE material is formulated. Closed-form expressions are built to conveniently evaluate model parameters. Furthermore, the FBCM method is validated by precise vehicles, and calculation results agree with the measurement with a maximum frequency error of 0.15% and a near-field magnitude error of 3.9 dB; all measured impedance and near-field components follow the characteristic described by FBCM. Finally, the radiation efficiency of a demonstrated PE antenna is calculated by FBCM to be 1.3e−9 for a single unit and 2.0e−9 for a PE antenna array, which is 5–67 times higher than that of a metallic electrical small antenna of the same size. The FBCM method can be an effective and convenient way for researchers to design and evaluate PE antennas in a short time.

Влияние наполнителя на деформацию полидиметилсилоксановых композитов под действием электрического поля

The study considers some aspects of the development of new stimuliresponsive materials capable to reversible deformation under an electric field due to the Maxwell pressure. To increase the response of the material to an external stimulus, an approach of polymer composites formation was chosen. Particles of various nature and shape were considered as fillers: powders of iron, montmorillonite and cellulose. Composite elastomeric materials based on polydimethylsiloxane with a low filler content of 5 wt% have been obtained. The morphology of the filler particles was confirmed by electron microscopy. Mechanical properties of the materials in uniaxial tests were studied. The Young’s modulus and constants for the 3-parameter Yeoh model in the range of deformations up to 800 % were determined. The electrophysical properties of the materials, as well as their response to an electric field at different strengths of 0.84 and 2.5 kV/mm have been studied. The effect of the filler nature on the conductivity and permittivity of composite materials was revealed. The data of mechanical and dielectric studies indicate that the filler concentration is below the percolation threshold for all composites. The composite with cellulose exhibits the greatest response to an external stimulus over the considered materials, which is determined by the balance of two factors: the value of Young’s modulus and the values of electrophysical characteristics. Directions for further research were determined and the prospects for the dielectric elastomers creation with predetermined properties were briefly discussed

A Miniaturized Wireless Passive Frequency Selective Surface Sensor for High-Temperature Applications

A passive and wireless sensor based on frequency selective surface (FSS) is presented for high-temperature applications. The sensor consists of a bent square loop array deposited in an alumina dielectric substrate. By inserting four symmetrical slots in the square loop structure, the dimension of the FSS unit cell is as compact as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.13 \lambda _{{0}}$ </tex-math></inline-formula> . The results show that the resonant frequency of the sensor decreases from 13.96 to 13.172 GHz with an average sensitivity of 0.81 MHz/°C when the temperature rises from 25 to 1000 °C. It was found that the resonant frequency shift is mainly attributed to the variations in permittivity of the substrate material. The sensor has a stable resonant frequency for both TE and TM polarizations under incident angles with a range of 0°–30°. The proposed sensor, which has the advantages of miniaturization, low profile, high sensitivity, and excellent angular stability, can be potentially applied in various harsh environments.

Imaging the Permittivity of Thin Film Materials by Using Scanning Capacitance Microscopy

Recently, great advances had been made by using scanning probe microscopy (SPM) to quantify the relative permittivity of thin film materials on a nanometer scale. The imaging techniques of permittivity for thin film materials with SPM, especially for photoelectric materials, have not been fully researched until now. Here, we presented a method to image permittivity of thin film materials by using a scanning capacitance microscope (SCM). This method combined the quantitative measurement by using SCM with the capacitance gradient–distance fitting curve to obtain the two-dimensional (2D) permittivity image at room temperature under atmospheric conditions. For the demonstration, a 2D permittivity image of film of molybdenum oxide (MoO3), a kind of photoelectric material, was acquired. From the image, it could be found that the average values of permittivity of MoO3 film and of MoO3 film-doped NaCl were about 8.0 and 9.5, respectively. The experimental results were quantitatively consistent with other experimental results of the same material. The reported technique here could provide a novel method for imaging the relative permittivity with nanometer resolution and be helpful for the study of photoelectric materials.

Investigating Imbert–Fedorov shift at a planner interface of dispersive–dissipative dielectric–magnetic metamaterial

The main objective of this paper is to analyze the spatial Imbert-Fedorov shift (IFS) on a planar interface of dispersive-dissipative dielectric-magnetic metamaterial. Spatial IFS is calculated by utilizing the energy flux method. The Lorentz–Drude Model is used to calculate the complex permittivity and permeability of frequency-dependent material. The behavior of spatial IFS is examined in both lossy and lossless mediums of transmission. Furthermore, spatial IFS is analyzed by varying the losses of dispersive–dissipative dielectric–magnetic metamaterial. The impact of the resonance frequency is also observed in this manuscript. DPS metamaterial behaves like an ordinary material and highest positive IFS with value of 33λ is observed for lossless case. ENG and MNG metamaterials behave like the metal and negative shifts are observed with the order of −0.014λ and −2λ respectively for lossy case. Because of the backward travelling wave, the DNG metamaterial has a negative shift. IFS observed for Lossless DNG metamaterial is −15λ, which is larger than the ENG and MNG metamaterials.

Deep neural network for retrieving material's permittivity from S‐parameters

AbstractThis research proposed a deep neural network (DNN) model employing a multilayer feedforward artificial neural network to characterize the relative permittivity and loss tangent of a solid sample in a broad frequency range from 1 to 10 GHz. The method exploited a grounded coplanar waveguide as a measurement fixture, and a vast amount of data was obtained from full‐wave simulations. The latter was used to train the proposed DNN model. We performed parametric studies to examine optimal DNN hyperparameters and improve the efficiency of the material property retrieval process. The proposed model was validated by retrieving the relative permittivity and loss tangent of a known substrate. The results show good agreement with the known reference values with a slight error of 1.2%.

Microwave Sensor Loaded With Complementary Curved Ring Resonator for Material Permittivity Detection

In the field of microwave measurement, how to miniaturize devices and improve measurement sensitivity is a major challenge. In this article, a planar microwave sensor loaded with a complementary curved ring resonator (CCRR) is proposed to measure the permittivity of substrate materials. The current forms a magnetic field along the path of the curved ring, which acts on the capacitance between the rings of the curved ring and makes the circuit resonate. At this time, the curved ring structure stores a huge amount of energy. When the substrate materials with different permittivity are loaded into the measurement area of the sensor, the resonant frequency of the sensor will change. By establishing a mathematical model between the permittivity and the resonant frequency and conducting a full-wave electromagnetic simulation, it can be seen that the CCRR combined with the substrate integrated waveguide (SIW) structure can effectively enhance the electric field intensity in the measured region. Compared with the conventional planar microwave resonator. The sensitivity, resolution, and size of the proposed sensor are 3.51%, 133 MHz, and 52 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 34 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 0.508 mm3, respectively. After optimizing the structural parameters of the sensor, the actual sensor was manufactured. Four kinds of substrate materials commonly used in microwave circuits are used as samples to test the sensor. The results show that the sensor has the characteristics of high sensitivity, high resolution, and high measurement accuracy, which confirms the promising application of the sensor in the field of permittivity measurement.

High-Contrast Low-Loss Antenna: A Novel Antenna for Efficient Into-Body Radiation

We present a biocompatible high-contrast low-loss antenna (HCLA) designed for efficient into-body radiation for applications as diverse as medical telemetry, sensing, and imaging. The HCLA is wearable with a compact size of 2.62 cm3 and operates across the 1 to 5 GHz bandwidth. The quasi-bowtie antenna is loaded with a high-contrast (i.e., alternating layers of high and low permittivity materials) and low-loss dielectric to improve directivity and gain into the biological tissues. Measurement results at 2.4 GHz are in good agreement with simulations and show 5.72 dB improvement in transmission loss over the most efficient into-body radiator reported in the past. At the high end of the frequency bandwidth, simulation results for two antennas placed across each other with tissue in between show ~12.5 dB improvement in transmission loss. The HCLA is fabricated with stable, low-loss materials that allow for repeatability and consistency in the fabrication process, thus, addressing limitations of the current state-of-the-art. It is also made from biocompatible materials that enable it to be placed directly on the skin for real-world implementation. In this paper, we discuss the operation principle and design of the HCLA, its transmission performance, radiation patterns, and specific absorption rate.

A Physical Framework to Interpret the Effects of High Permittivity Materials on Radiofrequency Coil Performance in Magnetic Resonance Imaging.

We propose a framework to interpret the effects of High Permittivity Materials (HPM) on the performance of radiofrequency coils in Magnetic Resonance Imaging (MRI). Based on a recent formulation of the scattering and propagation properties of spheres, we expanded the field in a layered sphere as a superposition of ingoing and outgoing travelling waves, which allowed us to study the field components with a non-homogeneous transmission line model. We investigated the effects of a layer of HPM surrounding a head-mimicking uniform sphere at 7 tesla. Through the analysis of impedance and reflection coefficients, we show that by adjusting the properties of the HPM, it is possible to selectively amplify individual modes, or combination of them, modifying the overall field distribution in the sample and increasing signal-to-noise ratio at specific locations. Our results demonstrate that the observed enhanced MRI performance is not merely due to secondary fields generated by displacement currents in the HPM. Our formulation explains the effect of HPM in terms of matching, enabling the optimization of the electrical properties of the HPM with a simple mode-matching formula. The proposed method could guide the design of novel radiofrequency coils with integrated HPM.

Transmittance properties of one-dimensional metamaterial nanocomposite photonic crystal in GHz range

We have theoretically demonstrated and explored the transmittance characteristics of a one-dimensional binary photonic crystal composed of metamaterial (MM) and nanocomposite (NC) layers. The NC layer was designed from silver nanoparticles (Ag-NPs) in a host material as Yttrium oxide (Y2O3). Using the transfer matrix approach (TMM), the optical properties of a one-dimensional binary periodic structure having MM and NC layers in the Giga Hertz (GHz) range were examined. The filling fractions of nanoparticles have been explored to see their effect on the effective permittivity of NC materials. Furthermore, the transmittance properties of the suggested structure were investigated at various incident angles for the transverse electric (TE) polarization. In addition to that, different parameters, such as the thickness of the MM layer, the permittivity of the host dielectric material, the filling fraction, and the thickness of the NC layer are also taken into account. We also discussed the effect of these parameters on the width of the photonic bandgap (PBG). With the optimum values of the optical parameters of NC layer, this research could open the way for better photonic crystal circuits, splitters, switches and others.

Optical, rheological, dielectric, and electrical properties of multiple oxides nanosuspended glycerol based semiconductor hybrid nanofluids

Semiconductor hybrid nanofluids (SHNFs) of multiple hybrid nano oxides (TiO2 + ZnO, TiO2 + Al2O3, TiO2 + SiO2, ZnO + Al2O3, and ZnO + SiO2) dispersed at fixed concentration (0.01 wt/wt%) in glycerol (Gly) fluid were prepared through solution mixing and probe ultrasonic cavitation process. These formulated SHNFs (i.e., TiO2 + ZnO/Gly, TiO2 + Al2O3/Gly, TiO2 + SiO2/Gly, ZnO + Al2O3/Gly, and ZnO + SiO2/Gly) were characterized by employing an ultraviolet–visible (UV–vis) spectrophotometer (wavelength range 200 – 800 nm), rheometer (shear rate range 1.32 – 5.28 s−1), and precision inductance–capacitance–resistance (LCR) meter (frequency range 50 Hz – 1 MHz). The dependency of UV–vis absorbance on the equal weight amount combinations of semiconductive and insulating nanosuspended hybrid oxides for these SHNFs was explored and analyzed for energy band gaps which showed strongly ruled by the wide band gap semiconductor TiO2 and ZnO materials. Dielectric permittivity, electrical conductivity, impedance, and electric modulus spectra of these SHNF materials were reported at 298.15 K and confirmed the influence of nanosuspended hybrids on the dielectric polarizations and relaxation behaviour. Dynamic viscosity and shear stress study with the shear rate explained the Newtonian behaviour of these SHNF materials. The multi-functionality of these novel SHNFs for the advances in soft condensed matter device/system technologies including optoelectronic, photovoltaic, UV-blocking, sensing, wavelength filtering, nanodielectric, electrical insulator, and thermal energy and mass transporter were demonstrated.

Transition of the colossal permittivity related dielectric relaxation in V-doped CaCu3Ti4O12 ceramics

The co-achieving of stable colossal permittivity (CP) and low dielectric loss in dielectric materials has been a challenge. In this paper, a transition in CP was observed in V-doped CaCu3Ti4O12 (CCTO) ceramics. The fast high-frequency dielectric relaxation that mainly contributed to CP of CCTO ceramics was greatly suppressed in V-doped CCTO samples. Its relaxation activation energy remained ∼0.10 eV, while its magnitude dropped from thousands in CCTO to dozens in V-doped CCTO. Instead, CP of V-doped CCTO ceramics mainly arose from another slow dielectric relaxation, which appeared in a much lower frequency range. Moreover, this dielectric relaxation gradually turned from a “carrier-dominated” relaxation into a “dipole-dominated” one with the increase in temperature. Its relaxation activation energy also changed from ∼0.06 to 0.42 eV in the meanwhile. These results indicated important roles of multiple point defects and their relating charge transport in CP behaviors. It supported that CP arose from electron trapping behaviors at the edge of double Schottky barriers at grain boundaries. On this basis, suppression of any deep-level point defects was concluded to be a potential clue to achieve both stable CP and sufficiently low dielectric loss in CCTO ceramics and other CP materials.

Double-ridged waveguide for efficiently heating ultrafine filament fibers

Microwave heating has attracted wide attention in fiber dyeing, refining, drying and modification due to its energy saving and environmental protection. However, effectively heating ultrafine filament fibers is difficult to achieve using conventional microwave heating devices because of their low power density and rapid heat dissipation at their surfaces. Thus, we designed a double-ridged waveguide operating at 2.45 GHz, facilitating rapid heating of ultrafine structure by increasing the electric field strength, subsequently causing higher power absorption by the ultrafine materials. First, the proposed waveguide was compared with other types of cavities by building a multiphysics model, incorporating electromagnetics and heat conduction of the heated filament fiber with a relative permittivity of 5.7–0.2j and a diameter of 0.008 times of the wavelength of vacuum. The electric field strength and power absorbed of the filament fiber located in the proposed ridged waveguide were approximately 13.3 and 180 times higher than that in WR430, a commonly used rectangular waveguide in system designs. Additionally, we built an experimental system to demonstrate that the design can efficiently heat a single filament fiber at low input power of 70 W. Furthermore, the effects of the filament fiber size, material permittivity, and cavity temperature on heating were investigated based on the constructed model.

Frequency reconfigurable dielectric lens antenna with graphene nano-antenna feed for THz applications

This paper proposes a frequency reconfigurable dielectric lens antenna (DLA) to compensate high attenuation due to atmospheric losses in the THz region. An aperture coupled graphene plasmonic nanoantenna has been designed and used to feed DLA. Frequency tuning has been introduced by varying the chemical potential of graphene. A lumped elements equivalent circuit for graphene-based feed antenna has also been proposed. The values of the lumped elements are obtained using the vector fitting algorithm. The proposed DLA has high gain, narrow beamwidth, broadside radiation pattern and stable input impedance. Directivity achieved through simulation is up to 7.3 dBi with radiation efficiency of 70 % and 21.2 dBi with radiation efficiency of 65 % for feed antenna and DLA respectively. The performance of DLA has also been studied as the function of feed element, relative permittivity of lens material, radius of lens and off-axis displacement tolerances.

New insight into the colossal dielectric permittivity and AC conductivity behavior of polycrystalline non-ferroelectric ceramics

The correlation of polarization with AC conductivity behavior of polycrystalline non-ferroelectric ceramics is more satisfied to be interpreted by three zones indicated in permittivity and AC conductivity spectra. These three zones concerning the dielectric and conductivity processes governing the response to an AC field have been identified in terms of the cluster model within the framework of percolation theory. Colossal dielectric permittivity of non-ferroelectric materials can be attributed to hopping polarization aligned via developing percolation clusters with high electron concentrations. The physical origin of the correlation between dielectric permittivity and AC conductivity of polycrystalline ceramics with respect to the effect of grain boundary has been clarified.

A Dielectric Sensor Based on Differential Microstrip Lines Coupled With Multiple Magnetic-LC Resonators

A differential microstrip lines-based microwave microstrip sensor loaded with multiple magnetic-LC (MLC) resonators is proposed in this manuscript. The proposed microstrip sensor is evolved from a traditional microstrip sensor, which has a single resonator unit excited by a single microstrip line. Based on the traditional one, the differential microstrip lines are added, which can improve the level of common-mode (CM) suppression. In the MLC resonator structure, a meander slot is embedded into the resonator to enhance the electrical field intensity. Three MLC resonators are etched on the bottom layer of the substrate, which can produce three transmission zeros (TZs) of differential mode (DM) due to the mutual coupling between these resonators and their own RLC equivalent circuit models. The three TZs can be regarded as three modes, the TZ in low-frequency band is the first odd-mode, the middle frequency TZ is even-mode, and the high-frequency TZ is the second odd-mode. As the resonance strength of the second odd-mode is relatively low; thus, it is ignored and the first odd-mode and even-mode are considered. Odd- and even-modes can be utilized to retrieve the permittivity of material under test (MUT). In the measurement, the error removal model is established to guarantee the experimental accuracy of MUT. The proposed microstrip sensor has average sensitivities of about 5.53% and 4.55% for odd- and even-modes, respectively. The proposed sensor has some superiorities to previous designs in terms of design structure, CM suppression, and multimode detection.

Ultralight N-doped platanus acerifolia biomass carbon microtubes/RGO composite aerogel with enhanced mechanical properties and high-performance microwave absorption

Biomass-derived carbon material, an ideal lightweight and sustainable electromagnetic wave (EMW) absorption material, has adjustable dielectric properties, which is one of its greatest advantages. However, how to comprehensively control its composite dielectric constant to achieve strong microwave absorption (MA), wide effective absorption bandwidth (EAB), light mass, and thin thickness is still challenging. In this study, the N-doped biomass carbon microtubes/RGO composite aerogel (N-BCMT/RGO) with a three-dimensional multistage pore network structure was prepared by using the waste Platanus acerifolia tree fruit-derived biomass microtubes as the base, through heteroatom doping and composite conductive material. Among them, the doping of nitrogen atoms introduces numerous defects and promotes the formation of a heterogeneous interface, which plays an important role in regulating conduction and polarization loss. Secondly, the introduction of conductive material effectively promotes the hopping and migration of electrons, which further enhances the conduction loss. Moreover, the close binding of BCMT and RGO causes N-BCMT/RGO aerogel to exhibit enhanced mechanical properties. The special multistage hole structure allows N-BCMT/RGO to exhibit good impedance matching and ultra-low density (0.0121 g/cm3), which also exhibits an ultra-wide EAB of 8.36 GHz and a minimum reflection loss (RLmin) of −55.45 dB at an ultra-low filler loading of 2 wt%. This opens up an avenue for the realization of novel microwave absorbers with light weight and high performance, and the proposed comprehensive control strategy for the composite permittivity of biomass-carbon materials provides new ideas for activating the MA behavior of metal-free carbon-based absorbers.

(Invited) The Long Reach of Impedance Measurements: From Flow Cells and Dielectrics to Experimental Artifacts

The motivation for this presentation is to bring into perspective experience in collecting and interpreting impedance data and put this in interesting and relevant form in front of specialists in electronic materials and processing.Impedance spectroscopy became very popular among electrochemists ever since most modern potentiostats started incorporating hardware for collecting impedance and software, for interpretation of putative equivalent circuits. The popularity stems both from usefulness of the method, when judiciously applied, and from the ease to obtain graphs suitable for pondering their meaning. In fact, the method became so commonplace that it acquired the acronym EIS which electrochemists somewhat vainly explain as the electrochemical impedance spectroscopy even though in many situations, it is spectroscopy just electrical as there may not be electrochemical processes even going on.The current turnkey potentiostats give capable electronic instrumentation to hands of people who do not need to be experts in electronic circuitry. This can lead to overinterpretation of data, particularly at higher frequencies. We will show on a case study how real-life input impedance of the instrument, which is typically and often successfully, ignored in data interpretation, can contribute to appearance of additional elements in fitted equivalent circuits.With the turnkey hardware is also provided powerful software as a tool for assignment of physical or chemical properties of the studied sample. On a case study of a dielectric electronic material with a leakage we will show how interpretation with overlooked leakage contribution leads to incorrect interpretation of material permittivity, indicating its frequency dependence.The attached figure shows impedance response of an active mass in a lead-acid battery studied for purpose of modern application for energy recuperation. This is one data set for an active lead acid mass 80 % discharged from a series of a full set of 0-100% discharged and 0-100% charged steps. The interpretation complication arises from the high frequency data (emphasized in the inset), where an inductor as an element in equivalent circuit might be called for. We will demonstrate how this response can be contributed to the real-life behavior of the impedance analyzer itself. Figure 1

Design Analysis of 5G Microstrip Antenna

5G communication network has three distinct characteristics, although not limited to; enhanced network coverage, low latency and massive device connectivity. 5G mobile system has broad spectrum to support high data rates. Such device must deploy corresponding radiating structures to meet the changing technological advancement. In this paper therefore, a microstrip patch antenna operating at 3.6GHz frequency is designed and simulated for 5G application. The choice of frequency of operation is influenced by the broad prospects for 5G. The substrate is the flame resistant four (FR4) with a dielectric constant of 4.6 and a loss tangent of 0.023. The results include; plots of the voltage standing wave ratio, radiation pattern, return loss and radiation efficiency. The result further showed that, the parameters influencing the radiation characteristics of the patch antenna are the relative permittivity of the dielectric material, the position of the slot on the patch, the ground plane, substrate type as well as the dimensions of the feed and patch. The microstrip antenna thus can be effectively deployed for 5G application.