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Recycled polyolefin as dielectric substrate for patch antennas
摘要： High-performance antennas operating at ultra-high frequency (UHF) are typically designed and fabricated using specialized radio frequency (RF) materials with low loss and consistent properties. This paper proposes and investigates the use of recycled polyolefin (high-density polyethylene and polypropylene) which is not specifically manufactured for RF applications and thus with unknown RF properties, as dielectric substrate for high-performance UHF patch antennas. As a demonstrative application, a polarization-reconfigurable patch antenna with dual feeds is designed and fabricated using adhesive copper foil on recycled polyolefin substrate. Depending on the feed’s magnitude and phase, different types of linear and circular polarizations can be achieved. The point of resonance for both ports is centered at 915 MHz with 10 dB return loss and bandwidth of 28 MHz. Port isolation is as low as ?17 dB with peak linear and circular gain of 7.0 dBi, and 7 dBiC, respectively, observed in all polarizations. The resulting antenna not only performs well, but is also lightweight, low moisture absorbent, mechanically sturdy, inexpensive and ecologically friendly arising from its use of recycled materials.
关键词： microstrip antennas,dielectric materials,polarization-reconfigurable,UHF antennas,dielectric measurements,recycled polyolefin
更新于2025-09-12 10:27:22
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Deficient or excessive CuO-TiO <sub/>2</sub> phase influence on dielectric properties of CaCu <sub/>3</sub> Ti <sub/>4</sub> O <sub/>12</sub> ceramics
摘要： The influence of the CuO–TiO2 phase (CT) on dielectric properties of the CCTO ceramic was investigated. CaCuXTiYO12 (CCXTYO) powders were prepared based on the coprecipitated method, where 2.70 ≤ x ≤ 3.30 and 3.25 ≤ y ≤ 4.75. XRD patterns confirmed the presence of CCTO and also the secondary phases as CuO, TiO2 and CaTiO3 for each sample and aided in its quantification. Scanning Electron Microscopy (SEM) shows secondary phases evolution in the grain boundaries, and its influence on size and morphology of the grains. Impedance spectroscopy measurements showed that the ceramics with lower amount of CuO and TiO2 phases (CT/deficient ceramics) exhibited the highest ?′ values (2.1x104 at 1kHz for CC2.9T3.75O ceramic). Also, CT/deficient ceramics showed lower tanδ values (0.090 at 1kHz for CC2.9T3.75O ceramic) than ceramics prepared with excessive CuO–TiO2 phase (0.241 at 1kHz for CC3.1T4.25O ceramics). The deficiency of CuO and TiO2 phases associated with high percentage of CCTO and CaTiO3 phases resulted in ceramics with the higher ?′ values.
关键词： CaCu3Ti4O12,titanates,dielectric materials properties,microstructure
更新于2025-09-10 09:29:36
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Structure development and dielectric properties of Zn-doped Pb([Mg,Fe],W)O <sub/>3</sub> perovskite ceramics
摘要： Ceramic samples of a pseudo-binary system Pb(Mg1/2W1/2)O3-Pb(Fe2/3W1/3)O3 (PMW-PFW) were prepared by solid-state reaction. In addition, their compositions were modified by 20 mol% Pb(Zn1/2W1/2)O3 (PZW) doping in order to investigate the role of zinc in the perovskite formation and dielectric properties. The perovskite contents were ≥95.1% at the overall composition range, except for a significantly low value of 79.0% at 0.8PFW-0.2PZW. The extension of sintering time for PMW accelerated superstructure formation, resulting in the ordering factor increased up to 0.40 after 12 h heat treatment. The maximum dielectric constant values increased with increasing PFW fractions. In comparison, the phase transition temperatures decreased sharply (by up to 161 ℃) at low concentrations of PFW, followed by mild changes (by up to 47 ℃) afterwards. The dielectric constant spectra were analyzed in terms of diffuseness characteristics, which reflected the phase transition modes quite well.
关键词： dielectric materials/properties,perovskites,ferroelectricity/ferroelectric materials,reaction
更新于2025-09-09 09:28:46
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Communication Two-Dimensional Electromagnetic Scattering and Inverse Scattering from Magneto-Dielectric Objects Based on Integral Equation Method
摘要： Efficient two-dimensional (2-D) full-waveform forward and inverse electromagnetic scattering solvers are presented in this paper. The combined field volume integral equation (CFVIE) is formulated in a layered medium. Different from the previous work, the mixed-order basis function is adopted in the discretization of the 2-D CFVIE. Meanwhile, the permittivity and permeability are simultaneously reconstructed in the inversion through the variational Born iteration method (VBIM), which is enhanced with a self-adaptive regularization factor and applied to the multi-frequency data. The proposed forward solver is validated by comparisons with the finite element simulations.
关键词： inverse scattering,magneto-dielectric materials,2-D CFVIE,VBIM
更新于2025-09-09 09:28:46
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Fundamentals of Electroceramics (Materials, Devices, and Applications) || Binding Forces in Solids and Essential Elements of Crystallography
摘要： In this chapter, we will study how the solids are held together in a structure that can be either polycrystalline or single crystal, how solids are classified based on their governing binding forces, the relationship between structures and the properties they acquire when subjected to an external agent such as an electric or a magnetic field, and, finally, how these properties help engineers and scientists develop devices and their applications. We will also study the nature and properties of single crystals and how their unique properties help us in understanding their importance to science and technology.
关键词： Dielectric Materials,Crystal Structures,Symmetry Elements,Crystallography,Binding Forces
更新于2025-09-09 09:28:46
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Characterization of additively manufactured cellular alumina dielectric structures
摘要： Additive manufacturing (AM, also known as 3D printing) can produce novel three-dimensional structures using low-loss dielectric materials. This enables the construction of dielectrics with complex shapes that enable innovative microwave applications such as resonators, filters, and metamaterial lenses. This paper addresses the production and characterization of cellular structures of various designed densities created with a low loss ceramic material, alumina (aluminum oxide), via vat photopolymerization. The permittivity of these printed structures is variable over roughly an octave, with a range of relative permittivites from 1.78 to 3.60, controlled via part geometry.
关键词： electromagnetic metamaterials,dielectric materials,ceramics,printing,design for manufacture
更新于2025-09-09 09:28:46
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On the propagation of Voigt waves in energetically active materials
摘要： If Voigt-wave propagation is possible in a dissipative anisotropic dielectric material characterised by the permittivity dyadic e, then it is also possible in the analogous energetically active material characterised by the permittivity dyadic e? , where e? is the hermitian conjugate of e. This symmetry follows directly from a theoretical analysis of the necessary and suf?cient conditions for Voigt-wave propagation in anisotropic materials. As a consequence of this symmetry, a porous dissipative material that exhibits Voigt-wave propagation can be used to construct a material that allows the propagation of Voigt waves with attendant linear gain in amplitude with propagation distance, by means of in?ltration with an electrically or optically activated dye, for example. This phenomenon is captured by the Bruggeman formalism for homogenised composite materials based on isotropic dielectric component materials that are randomly distributed as oriented spheroidal particles.
关键词： active materials,homogenised composite materials,Bruggeman formalism,anisotropic dielectric materials,Voigt-wave propagation
更新于2025-09-04 15:30:14
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[IEEE 2018 48th European Microwave Conference (EuMC) - Madrid, Spain (2018.9.23-2018.9.27)] 2018 48th European Microwave Conference (EuMC) - Extraction of Relative Permittivity from Measured Reflection Coefficient of Dielectric Materials in the Frequency Range 207 – 247 GHz
摘要： This work describes the use of millimetre wave technology to extract the dielectric constants of different types of dielectric materials. The extraction of the dielectric materials is based on measurements (i.e., monostatic measurements) of the reflection coefficient for various dielectric materials. The measurements are done by utilizing a frequency modulated continuous wave radar with a dielectric lens antenna. The investigated materials are broadly utilized as a part of our everyday life. The fundamental dielectric materials outcomes are done accompanying materials: Polytetrafluoroethylene (PTFE), mainly Teflon, nylon, and. The measurements are done in the frequency range from 207 GHz to 247 GHz.
关键词： reflection coefficient,material characteristics,corner reflector,millimeter wave length,dielectric materials,permittivity,measurement,lens antenna
更新于2025-09-04 15:30:14
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A sol-gel polymerization method for creating nanoporous polyimide silsesquioxane nanostructures as soft dielectric materials
摘要： A sol–gel polymerization method was developed to make polyimide (PI) silsesquioxane (SSQ) nanoparticles as functional, soft dielectric materials. The surface functionalization of the polymer chain backbone and chain ends of poly(trimellitic anhydride chloride-co-4,40-methylenedianiline), PMR-15 resin, with para-(chloromethyl)-phenylethyltrimethoxy silane yielded a novel sol–gel reactive sites functionalized PMR-silane precursor. Upon base-catalyzed hydrolysis and condensation of the PMR-silane precursor, spherical, raspberry-like PMR-SSQ nanoparticles were obtained in considerably good yield. Controlling the particle size distribution was attempted upon adjusting the molar ratio between the silane precursor and the base, as well as in the presence of a catalytic amount of silica sols. Particle composition, thermal stability, and morphology were confirmed from Fourier transform infrared, thermogravimetric analysis, and scanning electron microscopy analyses. Nanoparticles, visualized under transmission electron microscopy exhibit a nanoporous structure. The Brunauer–Emmett–Teller analysis confirmed that the average pore dimension is ranged from 2 to 5 nm. The dielectric constant of PMR-SSQ nanoparticles was as low as 1.95, compared to dielectric constants of 3.05 and 3.13 for PMR-15 and PMR-silane, respectively. Thus, the base-catalyzed sol–gel polymerization of alkoxysilylated PI offers a novel synthetic path to make functional nanoporous PI nanostructures that possess ultralow dielectric constants.
关键词： resin,polyimides,polymer functionalization,soft dielectric materials,thermoplastics
更新于2025-09-04 15:30:14
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Illusion Optics: Disguising with Ordinary Dielectric Materials
摘要： Illusion devices are usually designed using transformation optics. Here, a new method is proposed to achieve optical illusions without external devices by elaborately manipulating the scattering potential of an object. In contrast to the conventional transformation optics method, which completely replaces one object by the image of another object using complementary\restoring media and a superlens, the method described here is more of a cosmetic operation for an object, which modifies the scattering pattern of the object to mimic another object by exchanging their scattering potentials in two symmetrical areas in the wave vector domain. Only positive isotropic non-magnetic materials are introduced in the present method, which is impossible using the conventional method because superlenses require negative-index materials. Both numerical simulations and experimental demonstrations are used to verify the performance of the illusion devices of this method.
关键词： scattering potential,wave vector domains,illusion optics,isotropic dielectric materials
更新于2025-09-04 15:30:14