- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
[IEEE 2018 Second International Conference on Computing Methodologies and Communication (ICCMC) - Erode (2018.2.15-2018.2.16)] 2018 Second International Conference on Computing Methodologies and Communication (ICCMC) - Review report on the Effects of anisotropic and inhomogeneous permittivity on electromagnetic wave propagation
摘要： This research work deals with the ‘Effects of anisotropic, inhomogeneous permittivity and gravitation on electromagnetic wave propagation in waveguides’. Waveguide is a structure which can guide electromagnetic energy. Transportation of electromagnetic energy is one of the prime needs of a communication system. Communication engineers are in constant search of structures which can transport electromagnetic energy over long distances with minimum possible loss. Metallic waveguide can transport electromagnetic energy efficiently over frequencies ranging between few tens of kHz to few tens of GHz.
关键词： Anisotropic permittivity,anisotropic waveguide,inhomogeneous permittivity
更新于2025-09-23 15:21:01
-
[IEEE 2019 PhotonIcs & Electromagnetics Research Symposium - Spring (PIERS-Spring) - Rome, Italy (2019.6.17-2019.6.20)] 2019 PhotonIcs & Electromagnetics Research Symposium - Spring (PIERS-Spring) - Differentiation of the Laser Pulse in a Waveguide with a Bragg Grating
摘要： A novel one-port probe technique, which combines the measurements of a rectangular waveguide and coaxial probe to nondestructively yield the permittivity and permeability of a PEC-backed material, is presented. A brief description of the derivation of the theoretical probe reflection coefficients, necessary for permittivity and permeability extraction via numerical inversion, is provided. Experimental characterization results of a PEC-backed magnetic material are presented to validate the proposed approach. Error analysis is also undertaken to quantify the new technique’s sensitivity to common experimental errors.
关键词： moment methods,microwave measurements,waveguides,Integral equations,permeability measurement,uncertainty,permittivity measurement,measurement uncertainty
更新于2025-09-23 15:21:01
-
Electrical response in poled (Bi <sub/>0.5</sub> Na <sub/>0.5</sub> ) <sub/>0.935</sub> Ba <sub/>0.065</sub> TiO <sub/>3</sub> ceramics
摘要： A ferroelectric material (Bi0.5Na0.5)0.935Ba0.065TiO3 (BNBT) with a perovskite structure was poled and characterized by electrical impedance spectroscopy as a function of temperature, X-ray diffraction, and Rietveld refinement. The ac conductivity showed a low-frequency dispersion, supporting the idea of heterogeneous potential wells favored by Bi3+, Na+, and Ba2+ on the A site of the perovskite type of structure. The activation energies for ac conduction depend on the studied frequency. The permittivity and electrical modulus showed a distribution of the relaxation time associated with the delay in the orientation of the dipoles and an important contribution to the short-range conductivity.
关键词： electrical behavior,Rietveld refinement,Phase change,dielectric permittivity,BNBT
更新于2025-09-23 15:21:01
-
Broad-band measurements of dielectric permittivity in coaxial line using partially filled circular waveguide
摘要： The full-wave analysis was applied for a coaxial line (i.e., transmission line) that has a “short-circuited” discontinuity. The discontinuity has a radius less than or equal to the inner radius of the coaxial line. The “sample region” can be considered as a partially filled circular waveguide. Such a structure is very practical and is of particular interest for the dielectric spectroscopy applications. It takes into account the inhomogeneous field distribution, which is the limiting factor for the determination of high dielectric permittivity values at microwave frequencies. The direct problem was solved by using the mode-matching technique, and the relationship between the complex reflection coefficient and the dielectric permittivity of the cylindrical sample was obtained. By solving the inverse problem, it is possible to obtain the complex dielectric permittivity from the experimental values of the scattering matrix. The results were verified by the finite element modeling of the system and applied for particular materials. The correspondence between these approaches is excellent. This method is very suitable for the determination of permittivity, which exceeds several thousands (it is applicable for any type of material). It extends the frequency range where the permittivity can be determined reliably. There is no necessity to prepare samples with different geometries (i.e., surface area and thickness).
关键词： dielectric permittivity,coaxial line,circular waveguide,mode-matching technique,finite element modeling
更新于2025-09-23 15:21:01
-
[IEEE 2019 PhotonIcs & Electromagnetics Research Symposium - Spring (PIERS-Spring) - Rome, Italy (2019.6.17-2019.6.20)] 2019 PhotonIcs & Electromagnetics Research Symposium - Spring (PIERS-Spring) - Stability of Least Squares for the Solution of an Ill-posed Inverse Problem of Reconstructing Real Value of the Pcrrnittivity of a Dielectric Layer in a Rectangular Waveguide
摘要： We use the solution to Maxwell’s equations in a rectangular single-mode waveguide with multi-mode boundary conditions at its flanges to determine the parameters of the inclusion. The well-posedness of the inverse problem is studied using explicit expressions for the S-parameters of the waveguide when the inclusion is a plane-parallel dielectric slab. The methods of reconstructing permittivity from the measured (experimental) data must be stable and well-conditioned. The importance of these demands is discussed taking as an example the determination of real permittivity from noisy measurement data of the transmission coefficient of the principal waveguide mode. Generally, this problem is unsolvable because the range of the function to be inverted forms a set of measure zero on the complex plane. In addition, the occurrence of self-intersections of the parametric curve leads to non-uniqueness of the solution to the inverse problem. Therefore, approximate methods of the permittivity reconstruction in the vicinity of such points may be unstable or ill-conditioned. In our study, we present several examples of such algorithms. We demonstrate that the method of least squares applied for reconstructing permittivity of the inclusion from multi-frequency measurement data is a stable algorithm for the solution to this inverse problem. This approach does not use a priori estimates for the sought parameter and information about the location of singularities of the parametric curve. We determine the interval of variation of the condition number for the method of least squares and show that this quantity decreases as one of the following parameters increases: the width of the dielectric layer, the measurement frequency band, or its distance to the lower cutoff value. Using these results, we estimate the rate of convergence of the approximate solution to the exact value of the sought parameter when the quality of the measurement data is improved and show how to choose optimal parameters of the experiment and the measurement setup.
关键词： inverse problem,permittivity,Maxwell’s equations,waveguide,least squares method
更新于2025-09-23 15:21:01
-
[IEEE 2018 International Conference on Information and Telecommunication Technologies and Radio Electronics (UkrMiCo) - Odessa, Ukraine (2018.9.10-2018.9.14)] 2018 International Conference on Information and Telecommunication Technologies and Radio Electronics (UkrMiCo) - Micromechanical Tuning of Coplanar Waveguide Based Resonator
摘要： The paper extends idea of micromechanical tuning principle on coplanar waveguide based resonators. Finite elements and finite integral methods were used for electromagnetic problem solution. Presented simulation of signal electrode lift above substrate and dielectric body hover above the line surface demonstrates good tunability accompanied with low loss. Resonator based on tunable coplanar waveguide reaches tuning range up to 50% with displacement under 100 micrometres. Equivalent circuit of tunable CPW based band-stop stub filter is proposed.
关键词： frequency tuning,stub resonator,CPW,effective dielectric permittivity
更新于2025-09-23 15:21:01
-
Propagation of Electromagnetic Waves in an Open Planar Dielectric Waveguide Filled with a Nonlinear Medium II: TM Waves
摘要： A nonlinear eigenvalue problem on an interval is considered. The nonlinearity in the equation is specified by a nonnegative monotonically increasing function, and the boundary conditions nonlinearly depend both on the sought-for functions and on the spectral parameter. The discrete eigenvalues are defined using an additional (local) condition at one end of the interval. This problem describes the propagation of monochromatic (polarized) electromagnetic TM waves in a planar dielectric waveguide filled with a nonlinear medium. The nonlinearity covers a wide range of laws of nonlinear optics corresponding to self-interaction effects. Results on the solvability of the problem and the properties of the eigenvalues are obtained.
关键词： Maxwell’s equations,nonlinear eigenvalue problem,nonlinear permittivity,nonlinear Sturm–Liouville problem,planar dielectric waveguide,asymptotics of eigenvalues,comparison theorem
更新于2025-09-23 15:21:01
-
Polarizability of Radially Inhomogeneous Subwavelength Spheres
摘要： In this work the polarizability of a subwavelength core-shell sphere is considered, where the shell exhibits a radially inhomogeneous permittivity profile. The mathematical treatment of the electrostatic polarizability is formulated in terms of the scattering potentials and the corresponding scattering amplitudes. As a result, a generalized expression of the polarizability is presented to be dependent of the radial inhomogeneity function. The extracted general model is applied for two particular cases, i.e., a power-law profile and a new class of permittivity profiles that exhibit exponential radial dependence. The proposed analysis quantifies in a simple manner the inhomogeneity effects, allowing the direct implementation of naturally or artificially occurring permittivity inhomogeneities for a wide range of applications within and beyond the metamaterial paradigm. Specifically, a special case of symmetric-antisymmetric resonant plasmonic degeneracy is identified and shown for the case of a core-shell sphere with a power-law permittivity profile. This degeneracy could be used for the experimental identification of inhomogeneity-induced effects or for applications where a strong coupling resonant regime is required. Furthermore, the described analysis opens avenues towards the phenomenological and first-principles modeling of the electrodynamic scattering effects for graded-index plasmonic particles at the nanoscale. Finally, such a description can be readily used either for the benchmarking of novel computational methods incorporating inhomogeneous materials or for inverse scattering purposes.
关键词： inverse scattering,subwavelength,core-shell sphere,scattering potentials,metamaterial,exponential radial dependence,polarizability,scattering amplitudes,plasmonic degeneracy,radially inhomogeneous permittivity,power-law profile
更新于2025-09-23 15:21:01
-
Investigations of nano-crystalline Sr0.5Ba0.5Nb2O6 and bulk ceramics synthesized by a polymerization method using PEG400
摘要： Nano-crystalline Sr0.5Ba0.5Nb2O6 was synthesized by a one-pot method using PEG400 and citric acid. Calcination of the (Sr,Ba,Nb)-gel at 600 °C leads to Sr0.5Ba0.5Nb2O6 with a crystallite size of 24(2) nm and a specific surface area of 38.5(10) m2 g?1. Sintering up to 1325 °C leads to ceramics with globular or irregular-shaped grains and average grain sizes between 1.3 and 2.4 μm, whereas higher temperatures lead to a rod-like microstructure. The indirect allowed optical band gap varies between 3.70(5) and 3.29(5) eV. Dielectric measurements show a diffuse phase transition and weak relaxor properties. The maximum of the permittivity occurs between 116 and 147 °C. The frequency dependence of the impedance can be well described by one or two RC-circuits depending on sintering temperature. The melting temperature is determined as 1506(7) °C with ΔHf = 140(20) kJ mol?1. The average linear thermal expansion coefficient is found to be 10.5(5)?10?6 K?1.
关键词： Nano-particle,Strontium barium niobate,Band-gap,Dielectric permittivity,Tungsten bronze
更新于2025-09-23 15:21:01
-
Terahertz shielding properties of aero-GaN
摘要： The electrodynamic properties of the first aero-material based on compound semiconductor, namely of Aero-GaN, in the terahertz frequency region are experimentally investigated. Spectra of complex dielectric permittivity, refractive index, surface impedance are measured at frequencies 4-100 cm-1 and in the temperature interval 4 – 300 K. The shielding properties are found based on experimental data. The aero-material shows excellent shielding effectiveness in the frequency range from 0.1 THz to 1.3 THz, exceeding 40 dB in a huge frequency bandwidth, which is of high interest for industrial applications. These results place the aero-GaN among the best THz shielding materials known today.
关键词： Complex dielectric permittivity,THz shielding,Aero-GaN
更新于2025-09-23 15:19:57