Complex Resistive Boundary Condition Research Articles

Characteristics of HTS inverted circular patches on anisotropic substrates

In this study, an efficient full-wave method is developed for characterizing the resonant frequencies, bandwidths, and quality factors of an inverted circular superconducting patch antenna. Our technique is based on the Galerkin procedure in the Hankel transform domain (HTD) combined with the complex resistive boundary conditions. With the use of suitable Green’s functions in the HTD, the analysis is performed for the case where the superconducting circular patches is printed on an anisotropic substrate. The numerical results obtained using this approach are compared with the experimental results. These comparisons were very good, which proves the correctness and the validity of the method. It is found that the optical properties combined with optimally-chosen structural parameters of anisotropic materials can maintain control of the resonant frequency and exhibit wider bandwidth characteristics.

Inverted HTS rectangular patch antennas: Theoretical investigation

In this paper, we propose a full-wave analysis for characterizing the resonant frequencies and bandwidths of high-temperature superconductor inverted microstrip printed on anisotropic substrates. Our proposed approach is based on Galerkin procedure in the Fourier transform domain (FTD) combining with the complex resistive boundary condition. With the use of suitable Green's functions in the FTD, the analysis is performed for the case where the superconducting rectangular patches printed on anisotropic substrate. The numerical results obtained using the proposed approach are compared with previously published numerical results computed by means of the electromagnetic simulator “IE3D software”. These comparisons were very good, which prove the correctness and the validity of the proposed method. It is found that the optical properties combined with optimally chosen structural parameters of anisotropic materials can be maintaining control of the resonant frequency and exhibiting wider bandwidth characteristics.

RESONANT CHARACTERISTICS OF CIRCULAR HTC SUPERCONDUCTING PRINTED ANTENNA COVERED WITH A DIELECTRIC LAYER

—Effects of a superstrate layer on the resonant frequency and bandwidth of a high Tc superconducting (HTS) circular printed patch are investigated in this paper. For that, a rigorous full-wave spectral analysis of superconducting patch in multilayer configuration is described. In such an approach, the spectral dyadic Green's function which relates the tangential electric field and currents at various conductor planes should be determined. Integral equations are solved by a Galerkin's moment method procedure, and the complex resonance frequencies are studied with basis functions involving Chebyshev polynomials in conjunction with the complex resistive boundary condition. To include the superconductivity of the disc, its complex surface impedance is determined by using London's equation and the model of Gorter and Casimir. Numerical results are compared with experimental results of literature as well as with the most recent published calculations using different methods. A very good agreement is obtained. Finally, superstrate loading effects are presented and discussed showing interesting enhancement on the resonant characteristics of the superconducting antenna using combinations of Chebyshev polynomials as set of basis functions.

Superstrate loading effects on the resonant characteristics of high Tc superconducting circular patch printed on anisotropic materials

In this paper, the effects of both anisotropies in the substrate and superstrate loading on the resonant frequency and bandwidth of high-Tc superconducting circular microstrip patch in a substrate-superstrate configuration are investigated. A rigorous analysis is performed using a dyadic Galerkin's method in the vector Hankel transform domain. Galerkin's procedure is employed in the spectral domain where the TM and TE modes of the cylindrical cavity with magnetic side walls are used in the expansion of the disk current. The effect of the superconductivity of the patch is taken into account using the concept of the complex resistive boundary condition. London's equations and the two-fluid model of Gorter and Casimir are used in the calculation of the complex surface impedance of the superconducting circular disc. The accuracy of the analysis is tested by comparing the computed results with previously published data for several anisotropic substrate-superstrate materials. Good agreement is found among all sets of results. The numerical results obtained show that important errors can be made in the computation of the resonant frequencies and bandwidths of the superconducting resonators when substrate dielectric anisotropy, and/or superstrate anisotropy are ignored. Other theoretical results obtained show that the superconducting circular microstrip patch on anisotropic substrate-superstrate with properly selected permittivity values along the optical and the non-optical axes combined with optimally chosen structural parameters is more advantageous than the one on isotropic substrate-superstrate by exhibiting wider bandwidth characteristic.

High-Tc superconducting rectangular microstrip patch covered with a dielectric layer

This paper presents a full-wave method to calculate the resonant characteristics of rectangular microstrip antenna with and without dielectric cover, to explain the difference of performance with temperature between superconducting and normal conducting antenna. Especially the characteristics of high temperature superconducting (HTS) antenna were almost ideal around the critical temperature (Tc). The dyadic Green's functions of the considered structure are efficiently determined in the vector Fourier transform domain. The effect of the superconductivity of the patch is taken into account using the concept of the complex resistive boundary condition. The computed results are found to be in good agreement with results obtained using other methods. Also, the effects of the superstrate on the resonant frequency and bandwidth of rectangular microstrip patch in a substrate–superstrate configuration are investigated. This type of configuration can be used for wider bandwidth by proper selection of superstrate thickness and its dielectric constants.

EFFECTS OF SUPERSTRATE LAYER ON THE RESONANT CHARACTERISTICS OF SUPERCONDUCTING RECTANGULAR MICROSTRIP PATCH ANTENNA

The resonant characteristics of superconducting rectangular microstrip patch antenna with a superstrate layer are investigated using a full-wave spectral analysis in conjunction with the complex resistive boundary condition. The complex surface impedance of superconducting patch is determined using London’s equation and the two-fluid model of Gorter and Casimir. Numerical results using the full-wave analysis presented here are in excellent agreement with theoretical and experimental results available in the open literature. Numerical results show that the effect of the superstrate layer on the resonant frequency and half-power bandwidth of the superconducting rectangular patch is stronger than that of the structure without superstrate layer as both the thickness and permittivity of the superstrate increase. Finally, numerical results concerning the effects of the parameters of superstrate-substrate and superconducting patch on the antenna performance are also presented and discussed.

Characteristics of a high Tc superconducting rectangular microstrip patch on uniaxially anisotropic substrate

Resonant characteristics of a high Tc superconducting rectangular microstrip patch printed on uniaxially anisotropic substrate are investigated using a full-wave spectral analysis in conjunction with the complex resistive boundary condition. The uniaxial medium shows anisotropy of an electric type as well as anisotropy of a magnetic type. Both permittivity and permeability tensors of the substrate are included in the formulation of the dyadic Green’s function of the problem. The accuracy of the analysis is tested by comparing the computed results with previously published data for several anisotropic substrate materials. Numerical data of the resonant frequency and bandwidth as a function of electric anisotropy ratio are presented. Variations of the resonant frequency and bandwidth with the magnetic anisotropy ratio are also given. Finally, results showing the influence of the temperature on the resonant frequency and quality factor of the high Tc superconducting rectangular microstrip patch on a uniaxial substrate are also given.

Resonance of High Tc Superconducting Microstrip Patch in a Substrate-Superstrate Configuration

The effect of a protecting dielectric superstrate on the resonance of a high Tc superconducting microstrip patch is investigated. The analysis approach is based on the spectral-domain method of moments in conjunction with the complex resistive boundary condition. The complex surface impedance of the superconducting thin film is determined using London’s equation and the two-fluid model of Gorter and Casimir. Numerical results show that the resonant frequency of the high Tc superconducting rectangular patch decreases monotonically with increasing superstrate thickness, the decrease being greater for high permittivity loading.

Theoretical investigation of an air gap tuned superconducting triangular microstrip antenna

An analytical model is presented to improve the performance of the equilateral triangular microstrip antenna (ETMA). An improved model is presented taking into account the insertion of an air gap between the substrate and the ground plane, and High Tc superconducting material (HTS) for the triangular patch. The full-wave spectral domain technique in conjunction with the complex resistive boundary condition is used to calculate the characteristics including resonant frequencies, bandwidths, and radiation efficiency. Numerical results for the air gap tuning effect on the operating frequency and bandwidth of the high Tc superconducting triangular microstrip antenna (HTSTMA) are presented. The effect of temperature on resonant frequency and bandwidth of the HTSTMA are also given. The computed data are found to be in good agreement with results obtained using other methods.

Analysis of HighTcSuperconducting Rectangular Microstrip Patches over Ground Planes with Rectangular Apertures in Substrates Containing Anisotropic Materials

A rigorous full-wave analysis of highTcsuperconducting rectangular microstrip patch over ground plane with rectangular aperture in the case where the patch is printed on a uniaxially anisotropic substrate material is presented. The dyadic Green’s functions of the considered structure are efficiently determined in the vector Fourier transform domain. The effect of the superconductivity of the patch is taken into account using the concept of the complex resistive boundary condition. The accuracy of the analysis is tested by comparing the computed results with measurements and previously published data for several anisotropic substrate materials. Numerical results showing variation of the resonant frequency and the quality factor of the superconducting antenna with regard to operating temperature are given. Finally, the effects of uniaxial anisotropy in the substrate on the resonant frequencies of different TM modes of the superconducting microstrip antenna with rectangular aperture in the ground plane are presented.

Dual-Frequency Behavior of Stacked High T c Superconducting Microstrip Patches

The dual-frequency behavior of stacked high Tc superconducting rectangular microstrip patches fabricated on a two-layered substrate is investigated using a full-wave spectral analysis in conjunction with the complex resistive boundary condition. Using a matrix representation of each layer, the dyadic Green’s functions of the problem are efficiently determined in the vector Fourier transform domain. The stationary phase method is used for computing the radiation electric field of the antenna. The proposed approach is validated by comparison of the computed results with previously published data. Variations of the lower and upper resonant frequencies, bandwidth and quality factor with the operating temperature are given. Results showing the effects of the bottom patch thickness as well as the top patch thickness on the dual-frequency behavior of the stacked configuration are also presented and discussed. Finally, for a better comprehension of the dual-frequency operation, a comparison between the characteristics of the lower and upper resonances is given.

Efficient analysis for nonlinear microwave characteristics of high-power HTS thin filmmicrostrip resonators

This paper investigates the nonlinear effects ofhigh-Tc superconducting (HTS) thin film in high-power applications. A nonlinear model forcomplex surface impedance has been proposed for the efficient analysis of the nonlinearityof HTS thin films. Further, using the developed model, analysis of HTS-MSR hasbeen done using the spectral domain method (SDM). The SDM formulation hasbeen modified to account for finite conductivity and thickness of HTS films byincorporating a complex resistive boundary condition. The results have been validatedwith the experiments performed with microstrip resonators (MSRs) based onYBa2Cu3O7−x (YBCO) thin films made by a laser ablation technique onLaAlO3 substrates, characterized for their characteristics, namely, resonant frequency and qualityfactor measured as a function of temperature and input RF power. A close agreementbetween the theoretical and measured results has been achieved validating the analysis.

Characterization and analysis of high temperature superconducting microstrip andcoplanar resonators using a spectral domain method

Microwave characteristics of planar high temperature superconducting microstrip lineresonator (MSR) and coplanar waveguide (CPW) resonators have been estimated using afull wave spectral domain technique in conjunction with the complex resistive boundarycondition. The computer aided design method developed is applied to simulate thecharacteristics of planar resonators. The proposed method has been validated withexperimental results after taking into account the practical operating conditions. A reasonableagreement for the theoretically computed and measured resonant frequency and unloadedQ-value with experimental data of Porch et al (1995 IEEE Microw. Theory Technol. 2306–14) has been observed for the MSR operated at 5 GHz as well as for the CPWresonator at 7.95 GHz.

Analysis of superconducting microstrip lines and resonators using the complex resistive boundary conditions and the variational principle

A full wave characterization of high-temperature superconducting (HTS) microstrip lines and resonators is formulated based on the complex resistive boundary conditions (CRBC) of HTS. A variational approach is used to extend the applicable parameter range of the CRBC. >

Comments on "On the application of complex resistive boundary conditions to model transmission lines consisting of very thin superconductors" [with reply

In the original paper the authors present an elegant method to account for metallic losses in thin superconductors. The extensive numerical effort, which would otherwise be necessary to exactly solve the boundary-value problem, is considerably reduced by using the concept of complex resistive boundary conditions. This idea seems to have been originally introduced by Senior [1975]. The original authors reply to these comments. >

Characterization of power‐dependent high‐Tc superconducting microstrip line by modified spectral domain method

Surface resistance of the high‐Tc superconducting thin film may depend upon the power level of the thin film surface. An iteration method using the spectral domain technique with an application of complex resistive boundary condition is adopted to analyze such a nonlinear problem. Numerical results for the phase and attenuation constants and current distributions are given for different structural and material parameters.

Effect of tolerance on the propagation characteristic of a superconducting thin film microstrip delay line

The propagation constant of a superconducting microstrip transmission delay line is evaluated using the spectral domain immitance approach, modelling the superconductor as a surface current having an equivalent surface impedance found through the complex resistive boundary condition. The sensitivity approach is used to study the beta variations with substrate parameters and film characteristics. Results show that the surface impedance does not have much influence on beta sensitivities with respect to epsilon r, W and h. However, it can be observed that the surface impedance plays a crucial role in determining the optimum design.

On the application of complex resistive boundary conditions to model transmission lines consisting of very thin superconductors

A resistive boundary condition for the case where the resistivity is assumed to be a complex quantity is shown to be an accurate model for a superconducting film which is thin compared to the super-conducting penetration depth. The imaginary part of the conductivity is the dominant terms and is a measure of the inductive energy stored in the superconductor. Numerical solutions of superconducting microstrip are obtained and compared to experimental results and to analytic solutions for superconducting parallel-plate waveguides. Excellent agreement is found between experimental, analytical, and numerical results.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>