Browsing by Author "Bedra Sami"

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    An efficient study of circular microstrip antenna on suspended and composite substrates
    (Springer US, Journal of Computational Electronics, 2017) Bedra Sami
    In this paper, an efficient full-wave analysis of a circular microstrip patch printed on suspended and composite substrates is performed using a dyadic Green’s function formulation. Galerkin’s technique is used in the resolution of the integral equation of the electric field. The TM set of modes issued, from the magnetic wall cavity model, are used to expand the unknown currents on the circular patch. The radiation patterns are expressed regarding the transforms of the currents. The convergence of the method is proven by calculating the resonant frequencies, half-power bandwidths, and quality factors for several configurations. The computed results are found to be in excellent agreement with those observed in the literature. The numerical results obtained show that the bandwidth increases with the increase in the thickness of the suspended or composite substrates, especially for low permittivity of the second layer. Also, it is demonstrated that the resonant frequencies of the circular microstrip patch on suspended and composite substrates can be adjusted to obtain the maximum operating frequency of the antenna. Finally, the effect of the presence of the second layer under the circular patch on the radiation patterns is also investigated.
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    Analysis of a circular microstrip antenna on isotropic or uniaxially anisotropic substrate using neurospectral approach
    (Emerald Group Publishing Limited, COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, 2013) Bedra Sami
    The paper develops fast and accurate model based on ANN technique to calculate the resonant frequencies and quality factors of circular microstrip antennas. ANN is used to model the relationship between the parameters of the microstrip antenna and the resonant frequencies and quality factors obtained from the spectral domain approach. This relatively simple model allows designers to predict accurately the resonant frequencies and quality factors for a given design without having to develop or run the spectral method codes themselves. The main advantages of the method are: less computing time than the spectral model, results with accuracy equivalent to that of full-wave models and cost effectiveness, since the client can use a simple PC for implementation. Another advantage of the proposed ANN model is that it takes into account the uniaxial anisotropy in the substrate without increasing the network size. This is done by combining ANN with electromagnetic knowledge.
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    Analysis of elliptical-disk microstrip patch printed on isotropic or anisotropic substrate materials
    (Cambridge University Press, International Journal of Microwave and Wireless Technologies, 2016) Bedra Sami
    This paper presents a simple approach for accurate determination of the resonant frequency of an elliptical microstrip patch printed on isotropic or anisotropic substrate materials. In this approach, some modifications are made to account for fringe fields, dispersion effects, and losses by calculating effective dimensions, effective permittivity of anisotropy in the layer, and effective loss tangent, respectively. The theoretical resonant frequency results are in very good agreement with the experimental results reported elsewhere. Numerical results show that the change in the resonant frequency of the antenna is due primarily to a small disturbance of the substrate's nature. Then the effect of the uniaxial anisotropic materials is a significant parameter and most essential on the microstrip antenna characterization.
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    Analysis of high superconducting rectangular microstrip patches over ground planes with rectangular apertures in substrates containing anisotropic materials
    (Hindawi, International Journal of Antennas and Propagation, 2013) Bedra Sami
    A rigorous full-wave analysis of high superconducting 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.
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    Analysis of HTS circular patch antennas including radome effects
    (Cambridge University Press, International Journal of Microwave and Wireless Technologies, 2018) Bedra Sami
    In this paper, the resonant frequencies, quality factors and bandwidths of high Tc superconducting circular microstrip patches in the presence of a dielectric superstrate loading have been studied using Galerkin testing procedure in the Hankel transform domain. The exact Green's function of the grounded dielectric slab is used to derive an electric field integral equation for the unknown current distribution on the circular disc. Thus, surface waves, as well as space wave radiation, are included in the formulation. 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. Galerkin testing is used in the resolution of the electric field integral equation. Two solutions using two different basis sets to expand the unknown disk currents are developed. The first set of basis functions used is the complete set of transverse magnetic and transverse electric modes of a cylindrical cavity with magnetic side walls. The second set of basis functions used employ Chebyshev polynomials and enforce the current edge condition. The computed values for a wide range of variations of superstrate thickness and dielectric constant are compared with different theoretical and experimental values available in the open literature, showing close agreement. Results are showing that the superstrate parameters should always be kept into account in the design stage of the superconducting microstrip resonators.
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    Artificial Neural Network Model Analysis of Tunable Circular Microstrip Patch Antenna
    (IEEE Xplore, 2019 International Conference on Advanced Systems and Emergent Technologies (IC_ASET), 2019) Bedra Sami
    In this paper, in order to evaluate the resonant frequency of tunable circular microstrip patch with a fast and accurate model, neural networks are introduced in the theoretical analysis. The obtained model is very suitable for the CAD of microstrip patch antennas. The output of the artificial neuronal network which is the resonant frequency is shown to be very close to the experimental results reported elsewhere. Finally, the influence of the air separation on the operating frequency of the circular disc is investigated.
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    Bacterial foraging optimisation and method of moments for modelling and optimisation of microstrip antennas
    (The Institution of Engineering and Technology, IET Microwaves, Antennas & Propagation, 2014) Bedra Sami
    A novel technique applying bacterial foraging optimisation (BFO) in conjunction with the method of moments (MOM) is developed to calculate accurately the resonant frequency and bandwidth of rectangular microstrip antenna of any dimension and of any substrate thickness. The resonant frequency results obtained by using (BFO/MOM) algorithm are in very good agreement with the experimental results available in the literature. The computation time is greatly reduced as compared with the classical MOM. Furthermore, the idea of this paper can be used for calculating the various parameters of microstrip antennas of different structures and geometries.
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    Bedra Sami Characteristics of HTS inverted circular patches on anisotropic substrates
    (Springer US, Journal of Computational Electronics, 2021) Bedra Sami
    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.
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    CAD cavity model analysis of high Tc superconducting rectangular patch printed on anisotropic substrates
    (IEEE Xplore, 5th International Conference on Electrical Engineering-Boumerdes (ICEE-B), 2017) Bedra Sami
    This paper, present the resonant and the radiation characteristics of superconducting rectangular microstrip antenna printed on uniaxailly anisotropic substrate using an electromagnetic approach based on cavity model in conjunction with electromagnetic knowledge. The cavity model combined with London's equations and the Gorter-Casimir two-fluid model has been improved to investigate the resonant characteristics as well as the radiation patterns of high Tc superconducting rectangular microstrip patch in the case where the patch is printed on uniaxially anisotropic substrate materials. The most advantage of our extended model include low computational cost and mathematical simplify. The numerical simulation of this modeling shows excellent agreement with experimental results available in the literature. Finally, radiation patterns of superconducting rectangular patch on anisotropic substrate are also presented.
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    Computer-Aided Design of Superconducting Equilateral Triangular Patch on Anisotropic Substrates
    (EMW Publishing, Progress In Electromagnetics Research M, 2019) Bedra Sami
    The effects of both anisotropy in the substrates and the superconducting films on the resonant frequencies and radiation patterns of an equilateral triangular patch are investigated theoretically. Our proposed method is based on the modified cavity model in conjunction with the electromagnetic knowledge. The validity of the proposed method is tested by comparing the computed results of the resonant characteristics with the experimental data. Results show effects of the superconducting patch thickness as well as the anisotropy in the substrate on resonant frequency and the radiation pattern of the triangular patch. The effects of the antenna parameters on the resonant frequencies and radiation patterns are also presented and discussed. At higher substrate thicknesses, numerical results indicate that the radiation pattern is drastically changed. The resonant frequency, on the other hand, decreases with high equivalent permittivity of the anisotropic substrate. The proposed method is very fast, simple, and compatible well with CAD.
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    Effects of Superstrate Layer on the Resonant Characteristics of Superconducting Rectangular Microstrip Patch Antenna
    (EMW Publishing, Progress In Electromagnetics Research C, 2016) Bedra Sami
    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.
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    Efficient CAD Model to Analysis of High Tc Superconducting Circular Microstrip Antenna on Anisotropic Substrates
    (Advanced Electromagnetics, 2017) Bedra Sami
    In this paper, an electromagnetic approach based on cavity model in conjunction with electromagnetic knowledge was developed. The cavity model combined with London’s equations and the Gorter-Casimir two-fluid model has been improved to investigate the resonant characteristics of high Tc superconducting circular microstrip patch in the case where the patch is printed on uniaxially anisotropic substrate materials. Merits of our extended model include low computational cost and mathematical simplify. The numerical simulation of this modeling shows excellent agreement with experimental results available in the literature. Finally, numerical results for the dielectric anisotropic substrates effects on the operating frequencies for the case of superconducting circular patch are also presented.
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    Efficient full-wave analysis of resonant modes of circular microstrip antenna printed on isotropic or uniaxially anisotropic substrate
    (Springer US, Wireless Personal Communications, 2015) Bedra Sami
    In this work, the influence of uniaxial anisotropy in the substrate on the radiation pattern of circular microstrip antenna is investigated theoretically. The analytical approach is based on the spectral-domain method of moments in conjunction with the stationary phase method. A new concise expression is derived for computing the radiation electric field. The validity of the solution is tested by comparing the computed results with the experimental data. Finally, numerical results of the variations of resonant frequency and radiation patterns of the structure of higher order mode, with respect to the anisotropy ratio of the substrate, for several values of substrate thickness and patch radius are also presented.
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    Efficient full‐wave analysis of inverted circular microstrip antenna
    (Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2014) Bedra Sami
    In this article, a rigorous full-wave analysis for determining the resonant frequency and half-power bandwidth of inverted circular microstrip patch antenna is presented. Green's functions of the structure are determined in Hankel transform domain. Galerkin's is used in the resolution of the electric field integral equation. The TM set modes issued from the cavity model theory are used to expand to unknown current on the patch. The validity of the results is tested by comparing results with the experimental data. Also, numerical results for the variation of the resonant characteristics of the structure for high-order mode, and for several values of substrates thickness are presented.
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    Fast and Accurate Model to Determine the Resonant Characteristics of Elliptical Microstrip Patch Antenna
    (IEEE Xplore, 2019 International Conference on Advanced Systems and Emergent Technologies (IC_ASET), 2019) Bedra Sami
    In this work, artificial neural networks are used in the design of a microstrip antenna of elliptical geometry. We propose two neural models. In the first one, the outputs of the problem are the patch size and the resonant frequency for even modes. In the reverse side of the problem, the resonant frequencies for both even and odd modes are obtained in terms of the effective semi-major axis, eccentricity of elliptical patch, the thickness and the effective relative permittivity of the dielectric substrate. To enhance the accuracy of the two models, measurements have been included in the training stage. The two proposed models are very adequate for a fast and accurate estimation of the characteristics of the elliptical microstrip antenna.
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    Full-wave analysis of anisotropic circular microstrip antenna with air gap layer
    (EMW Publishing, Progress In Electromagnetics Research M, 2014) Bedra Sami
    In this paper, the effect of both uniaxial anisotropy in the substrate and air gap layer on the resonant frequency and bandwidth of circular microstrip patch are investigated. The problem is rigorously formulated based on the spectral domain technic in conjunction with Galerkin approach for computing the resonant frequency, half-power bandwidth, and radiation field of a tunable circular patch antenna which is printed on isotropic or uniaxial anisotropic substrate. The TM set of modes issued from the magnetic wall cavity model theory are used to expand the unknown currents on the patch. Resonant frequency shift due to uniaxial anisotropy is firstly investigated for different anisotropy ratio values of substrate. Then, the effect of inclusion of air gap layer inserted between anisotropic substrate and ground plane on the resonance characteristics is also investigated. The results obtained from this approach are in very good agreement with the experimental results available in the literature.
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    Hankel transform domain analysis of covered circular microstrip patch printed on an anisotropic dielectric layer
    (Springer US, Journal of Computational Electronics, 2015) Bedra Sami
    In the present paper, a rigorous full-wave analysis for determining the resonant frequency and half-power bandwidth of covered circular microstrip patch antenna is presented. Green’s functions of the structure are determined in Hankel transform domain. Galerkin’s is used in the resolution of the electric field integral equation. The TM set modes issued from the cavity model theory are used to expand to unknown current on the patch. For an isotropic substrate, it is demonstrated that the bandwidth decreases with increasing ratio of superstrate-substrate thickness for high permittivity and low thickness of superstrate. Also, we show that the resonant frequency and bandwidth are highly dependent on the permittivity variations along the optical axis. The validity of the results is tested by comparing results with those published in the literature. Also, numerical results for the variation of the resonant frequency and half-power bandwidth of the substrate-superstrate configuration for high order modes, and for several values of substrates thickness are presented.
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    High-Tc superconducting rectangular microstrip patch covered with a dielectric laye
    (Physica C: Superconductivity and its Applications, 2016) Bedra Sami
    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.
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    Inverted HTS rectangular patch antennas: Theoretical investigation
    (Elsevier, Physica C: Superconductivity and its Applications, 2021) Bedra Sami
    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.
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    Neurospectral computation for the resonant characteristics of microstrip patch antenna printed on uniaxially anisotropic substrates
    (Cambridge University Press, International Journal of Microwave and Wireless Technologies, 2017) Bedra Sami
    Modeling and design of rectangular microstrip patch printed on isotropic or anisotropic substrate are accomplished in this paper. The use of spectral domain method in conjunction with artificial neural networks (ANNs) to compute the resonant characteristics of rectangular microstrip patch printed on isotropic or anisotropic substrates. The moment method implemented in the spectral domain offers good accurateness, but its computational cost is high owing to the evaluation of the slowly decaying integrals and the iterative nature of the solution process. The paper introduces the electromagnetic knowledge combined with ANN in the analysis of rectangular microstrip antenna on uniaxially anisotropic substrate to reduce the complexity of the spectral domain method and to minimize the CPU time necessary to obtain the numerical results. The numerical comparison between neurospectral and conventional moment methods shows significant improvements in time convergence and computational cost. Hence, the use of neurospectral approach presented here as a promising fast technique in the design of microstrip antennas.