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- 2018
- arbitrary coupling coefficients
- Dielectric resonator
- filtering
- coupler
- filtering balun
- dual-band
- dual-mode dielectric resonator (DR)
- Electronic Science and Technology
- Nantong University
- Sun Yat-Sen University
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A high gain 60 GHz antipodal Fermi-tapered slot antenna based on robust synthesized dielectric
摘要： A high performance antipodal Fermi taper slot antenna based on unique synthesized dielectric is presented for ultra-wideband radar applications at 60 GHz band. Specifically, the synthesized dielectric is implemented based on machined holes concentrates only at aperture area to improve its mechanical robustness for lengthy antenna. Further, it is able to suppress back lobe level by 2.5 dB through curving tapered end of the antenna. Concurrently, sine corrugations and dielectric loading are adopted to improve radiation pattern and gain of the antenna for over 20 dB.
关键词： corrugation,dielectric,beamforming,ultra-wideband,tapered slot antenna
更新于2025-09-04 15:30:14
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Transport and complex modulus study of La0.7Ca0.3MnO3 perovskite manganite nano-compound with polypyrrole as host
摘要： The paper focuses on the facile synthesis of polypyrrole/La0.7Ca0.3MnO3 perovskite magnetic nano-composites synthesized by in situ chemical oxidation method using ammonium persulfate as oxidant. The morphology and crystal phase of the prepared samples were analyzed using SEM, TEM and XRD, respectively. Electrical conductivity, dielectric constant, dielectric loss, complex electric and impedance modulus studies were invested in the frequency range of 100 Hz–5 MHz at room temperature using AC impedance analyzer. The composites show frequency dependence with relaxation mechanism. The electric and impedance modulus analysis reveals the presence of non-Debye-type relaxation process and the effect of both grain and grain boundary on the transport properties of the composites.
关键词： Dielectric constant,Perovskite,Non-Debye relaxation,Electrical conductivity
更新于2025-09-04 15:30:14
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Enhanced dielectric strength and energy storage density in BaTi0.7Zr0.3O3 ceramics via spark plasma sintering
摘要： Barium zirconate titanate (BaTi0.7Zr0.3O3) ceramics were prepared via spark plasma sintering (SPS) and conventional solid-state sintering (CS). Both samples exhibited single phase nature as confirmed from the X-ray diffraction analysis. Compared with CS sample, more homogeneous microstructure with smaller grain size was observed in the SPS sample, which greatly improved the dielectric strength of BaTi0.7Zr0.3O3 ceramics from 40 (CS) to 170 kV/cm (SPS). Although the polarization of SPS sample was lower than that of CS sample under the same applied electric field, the maximum energy storage density was improved to 0.51 J/cm3, which was about 4.5 times higher than that of the CS sample (0.12 J/cm3). Moreover, finite element simulation on the local dielectric field distribution was carried out, and the effects of microstructure on the dielectric strength were further confirmed.
关键词： BaTi0.7Zr0.3O3,energy storage density,spark plasma sintering,dielectric strength
更新于2025-09-04 15:30:14
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Microwave cavity perturbation of nitrogen doped nano-crystalline diamond films
摘要： Non-contact and non-destructive electrical conductivity measurements of nitrogen doped nano-crystalline diamond films have been demonstrated using a microwave cavity perturbation system. The conductivity of the films was controlled by simply varying the CH4 gas concentration during microwave plasma assisted chemical vapour deposition, thereby promoting the formation of sp2 carbon at the grain boundaries. The presence of sp2 carbon is verified through Raman spectroscopy, x-ray photoelectron spectroscopy and electron energy loss spectroscopy, while scanning electron microscopy confirms an increasing surface area for sp2 to form. The microwave cavity perturbation results show that the measured cavity quality factor varies with CH4 concentration. The extraction of conductivity is achieved through a depolarisation model, which must be considered when the sample is smaller than the cavity and through both electric and magnetic field perturbations. The microwave measurements are comparable to contacting and damaging measurements when the film conductivity is greater than the substrate, thus demonstrating an invaluable method for determining conductivity without the need for depositing any electrodes on the film.
关键词： non-contact,microwave dielectric spectroscopy,nano-crystalline diamond,electrical conductivity
更新于2025-09-04 15:30:14
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Modeling Spin Coating over Topography and Uniformity Improvements through Fill Patterns for Advanced Packaging Technologies
摘要： An empirical model is proposed for predicting surface variations following dielectric spin coating (DSC) as applied to existing underlying topography in redistribution layer (RDL) fabrication. Test structures that represent a wide range of underlying feature widths, spacings, and heights are designed and fabricated. These are coated with multiple thicknesses of polyimide, and their surfaces are profiled and analyzed. An empirical model based on spatial filtering over underlying features is developed, with model parameters fit to coatings over a single feature for each set of process parameters. The model predicts post-coating thicknesses at the chip-scale. Comparisons between predictions and experimental results show an RMS error of 4.4% of the feature heights when averaged over each region profiled. Finally, fill patterns are designed and new test structures are simulated using these patterns. Simulation results suggest that global variations can be substantially reduced using such fill patterns, and these results are confirmed experimentally.
关键词： Process Modeling,2.5D Integration,Polyimide,Spin Coating,Fill Patterns,Dielectric Spin Coating,Re-Distribution Layers,RDLs,Packaging
更新于2025-09-04 15:30:14
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Structural, dielectric, and impedance study on ZnO doped Sr(Fe0.5Nb0.5)O3 ceramics
摘要： SrFe0.5Nb0.5O3 (SFN) ceramics doped with ZnO were synthesized via a conventional mixed oxide technique. Phase formation investigation by X-ray diffraction technique (XRD) revealed that all ceramic samples exhibited pure perovskite phase. Grain size as observed by an electron microscopy (SEM), was found to decrease with increasing the additive concentration. Dielectric properties and other related properties of the ceramics were also investigated. Very high dielectric constants > 3.3×105 (at temperature 250 °C and 1 kHz) were found for the 3 vol% doped samples. The impedance spectroscopy analysis suggested that the dielectric behavior of the samples could be linked with the Maxwell - Wagner polarization mechanism.
关键词： Perovskite,High dielectric constant,Ceramics,Maxwell - Wagner polarization,Impedance spectroscopy,SrFe0.5Nb0.5O3
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) - Efficient Excitation of a Toroidal Dipole Mode in All-Dielectric Quadrumer Clusters
摘要： We demonstrate a novel design of all-dielectric metasurfaces featuring strong axial toroidal response. A unit cell of the metamaterial is constructed by arranging two types of dielectric disks into an asymmetric quadrumer cluster. The toroidal response is achieved via the excitation of a trapped mode due to the symmetry breaking in the cluster. Dependence of the toroidal response on the degree of asymmetry in the cluster geometry, that appears from the different compositions of holes introduced into the disks, is studied both numerically and experimentally in the microwave regime.
关键词： metasurfaces,frequency selective surfaces,dielectric resonators
更新于2025-09-04 15:30:14
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A MINIATURIZED TUNABLE BANDPASS FILTER WITH CONSTANT FRACTIONAL BANDWIDTH
摘要： This paper presents a miniaturized tunable bandpass ?lter, consisting of two coaxial dielectric resonators and a pair of parallel-coupled lines. A coaxial dielectric resonators and a microstrip line form a new step-impedance resonator (SIR), which is di?erent from a conventional SIR. Varactor diodes are connected to SIRs to tune the center frequency. The gap between parallel-coupled lines controls the inter-stage coupling coe?cient. Lumped inductors used for coupling to I/O ports can reduce design complexity. The variations of coupling coe?cient and external quality factor with tuning frequency are analyzed using HFSS software. A appropriate coupling coe?cient which satis?es with constant fractional bandwidth within the tuning range is available. A tunable ?lter has been made of dielectric ceramics with dielectric constant of 38, fabricated on dielectric substrate and measured using Networks analyzer. Center frequencies vary from 0.43 GHz to 0.78 GHz, 3 dB fractional bandwidth from 6.4% to 6.8% when bias voltages are applied from 0 V to 10 V. The measured results validate the approach and agree with the simulation.
关键词： varactor diodes,constant fractional bandwidth,coaxial dielectric resonator,step-impedance resonator,tunable bandpass ?lter
更新于2025-09-04 15:30:14
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Liquid Crystal Tunable Dielectric Metamaterial Absorber in the Terahertz Range
摘要： In this paper, we propose a tunable dielectric metamaterial absorber in the terahertz (THz) range. The absorber is composed of a silicon pillar array embedded in a liquid crystal (LC) layer, which is sandwiched by two graphene electrodes. By way of varying the applied bias, the LC orientation can be continuously tuned. At a saturated bias, all LCs are vertically driven, and an absorption peak of 0.86 is achieved at 0.79 THz. When the bias is turned off, the same LCs are horizontally aligned, and the absorption peak degenerates into two smaller ones. A 47% modulation depth at 0.79 THz is obtained via numerical simulation with experimental feasibility considered. Such an active THz dielectric absorber may be utilized as part of various active THz apparatuses in THz imaging, sensing, switching, and filtering.
关键词： liquid crystal,metamaterial,dielectric absorber,terahertz,tunable
更新于2025-09-04 15:30:14
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Controllable coating polypyrrole on silicon carbide nanowires as a core-shell nanostructure: a facile method to enhance attenuation characteristics against electromagnetic radiation
摘要： Continuous polypyrrole (PPy) shells were coated on silicon carbide (SiC) nanowires to form core-shell nanostructures and the thicknesses of the shells were efficiently tuned through controlling the rate of polymerization. Compared with the composites loaded with pure SiC nanowires, the values of ε′ and ε′′ for the composites loaded with PPy@SiC nanowires were strengthened remarkably along with the increased thickness of the shells. The electromagnetic absorption (EA) bandwidth lower than ?10 and ?20 dB can be monitored in the area of 3.67-18.00 and 4.13-18.00 GHz, when 5 wt% of PPy@SiC nanowires were loaded in the composite. Meanwhile, the effective EA bandwidth can reach 6.88 GHz and the strongest reflection loss is ?58.6 dB.
关键词： dielectric properties,polypyrrole,silicon carbide nanowires,core-shell nanostructures,electromagnetic absorption
更新于2025-09-04 15:30:14