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Air-Filled Substrate Integrated Waveguide Fed Magneto-Electric Dipole Antenna Array for Millimeter-Wave Applications
摘要： A substrate integrated magneto-electric (ME) dipole antenna array with an improved radiation efficiency is presented in the 28-GHz band. A novel full-corporate air-filled substrate integrated waveguide (SIW) feed network with low losses is designed and realized by utilizing the low-cost printed circuit board (PCB) facilities. Different from most previous millimeter-wave planar arrays consisting of 2 × 2 sub-arrays, an SIW fed sub-array with a larger size of 2 × 4 is investigated to simplify the configuration of the major portion of the array feed network, which is of importance to the successful realization of the air-filled SIW feed network. An 8 × 8 array prototype with a four-layered geometry is fabricated and measured to verify the design. The array has an impedance bandwidth of 25.9%, a gain up to 26 dBi and stable radiation patterns over the operating band. Benefitted from the absence of the significant dielectric loss in the feed network, a high antenna efficiency of 80% is also achieved. The proposed design provides an effective method to improve the achievable gain and efficiency characteristics of the substrate-integrated arrays with a large size that are attractive for millimeter-wave wireless applications.
关键词： feed network,Antenna array,aperture-coupled magneto-electric (ME) dipole antenna,dielectric loss,millimeter-wave,air-filled substrate integrated waveguide (SIW)
更新于2025-09-11 14:15:04
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Direct Growth of a Polypyrrole Aerogel on Hollow CuS Hierarchical Microspheres Yields Particles with Excellent Electromagnetic Wave Properties
摘要： A current hot topic in polymer science is the development of electromagnetic wave-absorbing materials with desired properties (i.e., proper impedance matching and strong attenuation capability), but it presents a considerable challenge. In this work, solvothermal, and self-assembled polymerization were employed for the controlled fabrication of a uniform polypyrrole (PPy) aerogel coated on hollow CuS hierarchical microspheres (CuS@PPy). The PPy coating thickness of the heterostructure could be tuned by varying the feeding weight ratios of CuS/pyrrole monomer. The electromagnetic wave absorption properties of the CuS@PPy composites were estimated to be in the frequency range 2–18 GHz. The as-prepared Sample B (fabricated by the addition of 35 mg CuS) showed a maximum re?ection loss (RL) of ?52.85 dB at a thickness of 2.5 mm. Moreover, an ultra-wide effective bandwidth (RL ≤ ?10 dB) from 9.78 to 17.80 GHz (8.02 GHz) was achieved. Analysis of the electromagnetic properties demonstrated that the CuS@PPy had a remarkable enhancement compared to pure CuS platelet-based spheres and pure PPy, which can be attributed to the increased relatively complex permittivity and the promoted dielectric loss by the intense interfacial dielectric polarizations. We believe that the as-fabricated CuS@PPy can be a good reference for the fabrication of lightweight and optimal broadband absorbers.
关键词： core–shell,dielectric loss,electromagnetic absorption,polypyrrole
更新于2025-09-10 09:29:36
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Poly(vinylidene fluoride)/Plasma-Treated BaTiO3 Nanocomposites with Enhanced Electroactive Phase
摘要： Functional C=O and C-O groups are successfully fixated onto the surface of a high dielectric constant material barium titanate (BaTiO3) via non-thermal plasma. The strong dipole interaction exists between these functional groups and CH2 or CF2 groups of poly(vinylidene fluoride) (PVDF), resulting in the enhancement of the electroactive γ-phase of PVDF/BaTiO3 nanocomposites on one hand; on the other hand the dispersion of BaTiO3 is enhanced in the PVDF matrix, where the smaller spherulite size and better hydrophilic property are observed in the PVDF/plasma-treated BaTiO3 nanocomposite, comparing with the untreated ones. Therefore, the PVDF/plasma-treated BaTiO3 nanoparticles exhibited higher dielectric constant and lower dielectric loss than the PVDF/BaTiO3 nanoparticles.
关键词： plasma-treated barium titanate nanocomposites,dielectric constant,electroactive γ-phase,dielectric loss,poly(vinylidene fluoride) (PVDF)
更新于2025-09-09 09:28:46
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Electronic transport properties of (Se80Te20)100?xZnx (2?≤?x?≤?6) chalcogenide alloys
摘要： The bulk chalcogenide (Se80Te20)100-xZnx (2≤x≤6) alloys are prepared using melt quenching technique and electronic transport properties are studied in the frequency range 50 Hz–500 KHz and temperature range 400-520 K. The sharp peaks observed in X-ray diffraction pattern indicate the polycrystalline nature of prepared compositions. The measured dielectric properties and a.c. conductivity reveal the significant influence of Zn doping on the properties of the Se-Te matrix. The a.c. conductivity obeys Jonscher power law as ~ w s (s<1). To describe the conduction mechanism, the experimental results are analyzed in the framework of various theoretical models. The correlated barrier hopping (CBH) model successfully describe the observed frequency, temperature and composition response of ac conductivity.
关键词： a.c. conductivity,electronic transport properties,Chalcogenide alloys,dielectric constant,dielectric loss,X-Ray diffraction
更新于2025-09-09 09:28:46
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Investigation on Physical Properties of Semiorganic Nonlinear Optical Glycine Zinc Sulfate Single Crystal
摘要： Nonlinear optical single crystals of Glycine Zinc Sulfate (GZS) were grown by slow evaporation technique. Single crystal X-ray diffraction analysis revealed the crystal system and lattice parameter values. Powder X-ray diffraction analyses have been carried out and the diffraction patterns have been indexed. The optical properties of the crystals were determined using UV-Visible spectroscopy. Optical constants such as band gap, refractive index, extinction coefficient and electric susceptibility were determined from UV-Visible spectroscopy. The refractive index was determined using Brewster’s angle method. Hardness of the GZS crystal was estimated by Vicker’s hardness studies. Second Harmonic Generation (SHG) of GZS crystal was investigated by Kurtz powder technique. The dielectric constant and dielectric loss measurements were carried out for different temperatures and frequencies. The photoconductivity studies confirm that the grown crystal has negative photoconductivity nature. In order to investigate the growth mechanism and surface features, etching studies are carried out for the crystal.
关键词： NLO,single X-ray diffraction,SHG,UV-Vis-NIR spectrophotometer,dielectric loss studies,dielectric constant
更新于2025-09-09 09:28:46
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[IEEE 2018 IEEE 2nd International Conference on Dielectrics (ICD) - Budapest (2018.7.1-2018.7.5)] 2018 IEEE 2nd International Conference on Dielectrics (ICD) - Novel low dielectric loss polyimide film: synthesis and high frequency electrical properties
摘要： The thioether structure was introduced into the poly (N, N’- phenoxyphenyl pyromellitimide) (PMDA-ODA), owing to the extremely low dielectric loss of polyphenylene sulfide (PPS) in high frequency. Novel polyimide film containing 60% sulfide was synthesized through thermal imidization. The properties of these polyimide films morphology, thermal, dielectric characteristics and high frequency surface discharge lifetime, were studied. The films exhibited good thermal stability, having a mass loss less than 50% in decomposition temperature at 800 ?C. The phenyl sulfide containing polyimide films showed a lower dielectric loss tangent and longer lifetime in the effect high frequency high voltage surface discharge. The novel polyimide is more suitable in the insulation application of high frequency power electronic devices.
关键词： lifetime,high frequency,polyimide,phenyl sulfide,dielectric loss
更新于2025-09-09 09:28:46
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Preparation of Ultra-low Temperature Sintering Ceramics with Ultralow Dielectric Loss in Na <sub/>2</sub> O-WO <sub/>3</sub> Binary System
摘要： A series of new microwave dielectric ceramics with ultralow dielectric loss in Na2O-WO3 binary system were prepared by the modified solid-state reaction method at ultra-low sintering temperatures. Three stable phases, namely Na2WO4, Na2W2O7 and Na2W4O13, were formed in the system. Their stability in the air, phase composition, compatibility with metal electrodes, microstructures and microwave dielectric properties were investigated. In this binary system, the cubic structure Na2WO4 ceramic sintered at 565?C exhibited the best microwave dielectric properties with a permittivity of 5.6, a Q × f value of 124 200 GHz and a temperature coefficient of -63 ppm/?C at a frequency of 13.1 GHz. The Na2WO4 ceramic is chemically compatible with Ag and Al electrodes. Besides, the Na2WO4 ceramic has favorable stability in the air. Due to the excellent dielectric properties and favorable stability in the air, the Na2WO4 ceramic is a great candidate for LTCC devices.
关键词： Ultra-low dielectric loss,Microwave dielectric ceramics,Ultra-low firing
更新于2025-09-04 15:30:14
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Dielectric Properties of NaCu <sub/>3</sub> Ti <sub/>3</sub> Nb <sub/>1–x</sub> Sb <sub/>x</sub> O <sub/>12</sub> Ceramics
摘要： In order to investigate the influence of Sb doping on the dielectric properties of NaCu3Ti3NbO12 ceramics, a series of NaCu3Ti3Nb1–xSbxO12 ceramics were prepared by conventional solid-state reaction technique. Their crystalline structure, microstructure, dielectric properties and complex impedance were systematically investigated. All these ceramics show giant permittivity phenomenon, and their low-frequency dielectric loss decrease significantly but permittivity remains large with increased Sb doping. Impedance spectroscopic analysis reveals that NaCu3Ti3Nb1–xSbxO12 ceramics are composed of insulating grain boundaries and semiconducting grains, and their resistance of grain boundary increases with increased Sb doping. According to internal barrier layer capacitance effect, the decrease of low-frequency dielectric loss in NaCu3Ti3Nb1–xSbxO12 ceramics with increased Sb doping should be caused by the increase of grain boundary resistance.
关键词： Internal barrier layer capacitance effect,NaCu3Ti3Nb1–xSbxO12 ceramics,Grain boundary resistance,Low-frequency dielectric loss
更新于2025-09-04 15:30:14