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1 – 10 of over 1000Kanchana D., Radha Sankararajan, Sreeja B.S. and Manikandan E.
A novel low profile frequency selective surface (FSS) with a band-stop response at 10 GHz is demonstrated. The purpose of this designed FSS structure is to reject the X-band (8-12…
Abstract
Purpose
A novel low profile frequency selective surface (FSS) with a band-stop response at 10 GHz is demonstrated. The purpose of this designed FSS structure is to reject the X-band (8-12 GHz) for the application of shielding. The proposed FSS structure having the unit cell dimension of 8 × 8 mm2, the miniaturization of the FSS unit cell in terms of λ0 is 0.266 λ0 × 0.266 λ0, where λ0 is free space wavelength. The designed FSS provides 4 GHz bandwidth with insertion loss of 15 dB. The transverse electric (TE) and transverse magnetic (TM) modes of the proposed design are same because of polarization independent characteristics and hold the angularly stable frequency response for both TE and TM mode polarization. Both the simulation and measurement results are in good agreement to each other.
Design/methodology/approach
The proposed FSS design contains square-shaped PEC material, which is placed on the substrate and the shape of the circle and rectangle is etched over the PEC material. The PEC material of the patch dimension is 0.0175 mm. The substrate used for the proposed design is FR4 lossy with the thickness of 0.8 mm and permittivity εr = 4.3 having a loss tangent of 0.02.
Findings
To find a new design and miniaturized FSS structure is discussed.
Originality/value
100%
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Keywords
Mario A. Rodriguez Barrera and Walter Pereira Carpes Jr
The purpose of this paper is to present the results of a particle swarm optimization (PSO) method applied in the design of a square-loop frequency selective surface (FSS) via the…
Abstract
Purpose
The purpose of this paper is to present the results of a particle swarm optimization (PSO) method applied in the design of a square-loop frequency selective surface (FSS) via the equivalent circuit model (ECM), considering the dielectric effective permittivity as a variable in the optimization problem.
Design/methodology/approach
In the optimization process considered, besides the FSS square loop geometric parameters, the thickness and relative permittivity of dielectric material used as support are included as variables in the search space, using for this a model of dielectric effective permittivity introduced by the authors in a previous work.
Findings
Square loops were designed and the obtained results were compared with designs reported in literature for applications in wireless local area network and long-term evolution 4G systems. The low computational cost is remarkable as well as the acceptable accuracy obtained with the proposed approach. The PSO method results were implemented with the ECM and compared with those obtained via Ansys – high frequency structure simulator commercial software simulations.
Originality/value
The lack of a model of dielectric effective permittivity for the ECM causes a restricted search space in the stochastic FSS design process limited to only geometric parameters, as it is reported in the available literature. The proposed approach simplifies and makes more flexible the design process, and allows guiding the FSS design to unit cell surface and/or dielectric thickness of small dimensions.
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In this article, the authors intended to analyze the shielding properties of a fabric frequency selective surface (FSS) structure to the basis of substrate fabric properties. For…
Abstract
Purpose
In this article, the authors intended to analyze the shielding properties of a fabric frequency selective surface (FSS) structure to the basis of substrate fabric properties. For this purpose, the effect of the properties and structural parameters of the substrate fabric layer were analyzed on the shielding properties of the developed FSS.
Design/methodology/approach
The experimental and theoretical evaluations were done at the frequency band of 1,805–1,880 MHz and computer simulation technology (CST) was used in modeling. In experiments were developed the FSS structures by different fabrics as the substrate layers and the copper as the patch cells. The shielding properties of these samples were measured experimentally by the developed setup.
Findings
Confirming resonant frequencies, transmission coefficients, and the bandwidths results obtained from modeling and experiments show that the thickness, weight and interweaving structure parameters were affect the porosity of the substrate fabric. Porosity of the fabric moves the resonant frequency due to the changing of the dielectric properties of the fabric. Therefore, shielding properties of the FSS structure were affected by these parameters as the important characteristics of the substrate fabric. In addition, shielding properties of the samples (resonant frequencies and transmission coefficients) in different incident angles are not same in two modes of transverse electric and transfer magnetic.
Originality/value
The experimental results suggest that the introduced flexible FSS structures are suitable for shielding applications in the proposed frequency band.
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Keywords
Quan-Quan Wang, Hong-Bo Zhu, Ru-Shan Chen and Yun-Qin Hu
Analysis of the frequency selective surface (FSS) is of great significance. In the method of moments, when the electric size of the FSS increases, huge in-core memory and CPU time…
Abstract
Purpose
Analysis of the frequency selective surface (FSS) is of great significance. In the method of moments, when the electric size of the FSS increases, huge in-core memory and CPU time are required. The purpose of this paper is to efficiently analyze the finite FSS backed by dielectric substrate utilizing sub-entire-domain (SED) basis function method.
Design/methodology/approach
Different types of SED basis functions are generated according to the locations of the cells in the entire structure, and a reduced system is constructed and solved. The couplings of all cells of the FSS are taken into account by using Green’s function and Galerkin’s test procedure. The spatial Green’s function is obtained with the discrete complex image method. The reflection and transmission coefficients of the FSS are calculated using the far field of the FSS and the metallic plate with the same size.
Findings
Moderate problems of the finite FSS backed by dielectric substrate are solved with the SED basis function method. The original problem can be simplified to two smaller problems. It enables a significant reduction to the matrix size and storage, and efficient analysis of FSS can be performed. The band-stop type of FSS can be composed of periodic conductive patch cells on the dielectric substrate, and shows total reflection property at the resonant frequency.
Originality/value
The SED basis function method is mostly used to analyze periodic PEC structures in free space. The layered medium Green’s function is successfully employed and several dielectric substrate backed finite FSSs are discussed in this paper. The calculation of reflection and transmission coefficients, which are more effective rather than far field scattering of the FSS, are described.
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Davide Ramaccia, Filiberto Bilotti, Alessandro Toscano and Lucio Vegni
– The purpose of this paper is to design simple and high-performing screens capable to separate circularly polarized electromagnetic waves in Ku band from the ones in Ka band.
Abstract
Purpose
The purpose of this paper is to design simple and high-performing screens capable to separate circularly polarized electromagnetic waves in Ku band from the ones in Ka band.
Design/methodology/approach
The proposed screen consists of an inductive double resonant element FSS, i.e. a regular array of circular holes in a metal thick plate, in order to grant the robustness to mechanical stress for antenna applications in extreme conditions.
Findings
The proposed design of a multi-band frequency selective surface (FSS) is able to separate circularly polarized electromagnetic waves in Ku band from the ones in Ka band.
Originality/value
The paper shows the capabilities of a novel FSS that combine the transmission properties of two simple FSSs which allows us to achieve an interesting behaviour in three typical bands of the satellite communications.
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Tomas Halleröd, David Ericsson and Anders Bondeson
Shape and material parameters have major influence on the performance of electromagnetic components. Optimization of these parameters is therefore vital in electromagnetic design…
Abstract
Purpose
Shape and material parameters have major influence on the performance of electromagnetic components. Optimization of these parameters is therefore vital in electromagnetic design. Reduction of the radar cross section (RCS) for aircraft and frequency selective surfaces are two well known examples. Shape and materials optimization is performed for different scatterers in 2D.
Design/methodology/approach
Continuum design sensitivities for microwave problems are applied for the gradient‐based optimization of scatterers' shape and material parameters. The goal function is chosen to be an average of the monostatic RCS for a sector of incident angles over a frequency band. Numerical tests are presented for 2D scatterers and, specifically, a perfectly electrically conducting scatterer and an absorber on the front edge of an airplane wing are considered. The results are compared with theoretical findings and results in the open literature.
Findings
It is demonstrated that a dense frequency sampling of the goal function over a wide frequency band relaxes the requirements on the angular resolution. The broad band requirements on the RCS also avoids corrugations without the resorting to regularization methods and penalty terms added to the goal function. The optimization algorithm refines, in a small number of iterations, the initial geometry of the scatterer to an optimized design with strongly reduced RCS.
Originality/value
Shape and material parameters have major influence on the performance of electromagnetic components. Optimization of these parameters for scatterers demonstrates that a densely evaluated goal function over a broad frequency band has the advantages of: lowering the requirements on angular resolution; avoiding corrugations; and regularizing the problem by the broad frequency band requirements which often are naturally included in the performance specification of electromagnetic devices.
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Ugo d'Elia, Giuseppe Pelosi, Stefano Selleri and Ruggero Taddei
A design procedure for multi-layer absorbers based on carbon nanotubes (CNT) frequency selective surfaces (FSS) sheets is here developed. The paper aims to discuss there issues…
Abstract
Purpose
A design procedure for multi-layer absorbers based on carbon nanotubes (CNT) frequency selective surfaces (FSS) sheets is here developed. The paper aims to discuss there issues.
Design/methodology/approach
Single layer FSS are first analyzed via finite element (FE). Then equivalent sheets admittances are extracted in a transmission line model. Neural networks (NNs) interpolation over this data and subsequent multi-objective genetic algorithm (GA) based optimizations are then performed to design multiple layers absorbing structures. Designs are finally validated via full wave FEM simulations.
Findings
In this paper, some absorbing structures made of three or four FSS sheets with total thicknesses around 6 mm are synthesized.
Research limitations/implications
NNs' accuracy used in the equivalent model can be refined with further training.
Practical implications
Low profile absorbing materials are of relevant industrial interest both for radar cloaking and anechoic chambers.
Originality/value
The transmission line model combined with NNs and GA optimization is capable of speeding up the design procedure with respect to a conventional full-wave FEM approach.
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Khader Zelani Shaik, Siddaiah P. and K. Satya Prasad
Millimeter wave spectrum represents new opportunities to add capacity and faster speeds for next-generation services as fifth generation (5G) applications. In its Spectrum…
Abstract
Purpose
Millimeter wave spectrum represents new opportunities to add capacity and faster speeds for next-generation services as fifth generation (5G) applications. In its Spectrum Frontiers proceeding, the Federal Communications Commision decided to focus on spectrum bands where the most spectrums are potentially available. A low profile antenna array with new decoupling structure is proposed and expected to resonate at higher frequency bands, i.e. millimeter wave frequencies, which are suitable for 5G applications.
Design/methodology/approach
The presented antenna contains artificial magnetic conductor (AMC) surface as decoupling structure. The proposed antenna array with novel AMC surface is operating at 29.1GHz and proven to be decoupling structure and capable of enhancing the isolation by reducing mutual coupling as 8.7dB between the array elements. It is evident that, and overall gain is improved as 10.1% by incorporating 1x2 Array with AMC Method. Mutual coupling between the elements of 1 × 2 antenna array is decreased by 39.12%.
Findings
The proposed structure is designed and simulated using HFSS software and the results are obtained in terms of return loss, gain, voltage standing wave ratio (VSWR) and mutual coupling. The S-Parameters of each stage of design is tabulated and compared with each other to prove the decoupling capability of AMC surface in antenna arrays.
Originality/value
The proposed structure is designed and simulated using HFSS software, and the results are obtained in terms of return loss, gain, VSWR and mutual coupling. The S-Parameters of each stage of design is tabulated and compared with each other to prove the decoupling capability of AMC surface in antenna arrays.
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Tae-Bong Lee and Min-Nyeon Kim
– The purpose of this paper is to analyze far and near field emitted field patterns through more exact calculation of the modes formed in finite periodic dielectric gratings.
Abstract
Purpose
The purpose of this paper is to analyze far and near field emitted field patterns through more exact calculation of the modes formed in finite periodic dielectric gratings.
Design/methodology/approach
For the mode calculation, equations are newly defined by applying vertical boundary condition on the assumption that transverse electric modes are generated in the structure. After finding modes, near field patterns are calculated using the wave number and coefficient of the mode.
Findings
Additionally, the results from these calculations are compared with that of the rigorous-coupled method. Finally, far field patterns are derived by applying fast Fourier transform to near field patterns and also compared with the results of rigorous-coupled method.
Research limitations/implications
For convenience of coordinate, we use rectangular coordinate, though the shape of radome is a hemisphere.
Practical implications
In this paper, the authors derive more exact near field patterns without the assumption of infiniteness so that these results can be used practically for a making real frequency-selective structure.
Originality/value
Conventional periodic finite dielectric gratings analysis has been done using Floquet–Bloch wave theory, coupled-mode, rigorous-coupled method which is based on the assumption of infiniteness of the structure.
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Goksel Saracoglu, Serap Kiriş, Sezer Çoban, Muharrem Karaaslan, Tolga Depci and Emin Bayraktar
The aim of this study is to determine the fracture behavior of wool felt and fabric based epoxy composites and their responses to electromagnetic waves.
Abstract
Purpose
The aim of this study is to determine the fracture behavior of wool felt and fabric based epoxy composites and their responses to electromagnetic waves.
Design/methodology/approach
Notched and unnotched tensile tests of composites made of wool only and hybridized with a glass fiber layer were carried out, and fracture behavior and toughness at macro scale were determined. They were exposed to electromagnetic waves between 8 and 18 GHz frequencies using two horn antennas.
Findings
The keratin and lignin layer on the surface of the wool felt caused lower values to be obtained compared to the mechanical values given by pure epoxy. However, the use of wool felt in the symmetry layer of the laminated composite material provided higher mechanical values than the composite with glass fiber in the symmetry layer due to the mechanical interlocking it created. The use of wool in fabric form resulted in an increase in the modulus of elasticity, but no change in fracture toughness was observed. As a result of the electromagnetic analysis, it was also seen in the electromagnetic analysis that the transmittance of the materials was high, and the reflectance was low throughout the applied frequency range. Hence, it was concluded that all of the manufactured materials could be used as radome material over a wide band.
Practical implications
Sheep wool is an easy-to-supply and low-cost material. In this paper, it is presented that sheep wool can be evaluated as a biocomposite material and used for radome applications.
Originality/value
The combined evaluation of felt and fabric forms of a natural and inexpensive reinforcing element such as sheep wool and the combined evaluation of fracture mechanics and electromagnetic absorption properties will contribute to the evaluation of biocomposites in aviation.
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