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Article
Publication date: 11 November 2013

Alessio Monti, Luca Scorrano, Simone Tricarico, Filiberto Bilotti, Alessandro Toscano and Lucio Vegni

The purpose of this paper is to show how metamaterials with extreme values of permittivity and permeability, may be effectively used to design artificial magnetic…

Abstract

Purpose

The purpose of this paper is to show how metamaterials with extreme values of permittivity and permeability, may be effectively used to design artificial magnetic conductors (AMC) at a given frequency. In particular, this paper theoretically determines, for the different polarizations of the incidence field, the conditions under which metamaterials can behave as an AMC.

Design/methodology/approach

In order to find out the required values of the constitutive parameters, this paper has done a theoretical analysis based on the transmission-line theory. The obtained analytical reflection coefficient has been particularized for the different possible polarizations of the incidence field in order to find the constitutive parameters values that this paper needs for the AMC behavior.

Findings

Depending on the polarization of the field, it is shown that different values of the constitutive parameters are needed to get AMCs. In particular, it is shown that in the case of TEM and TE polarizations, a large value of the permeability is enough to obtain an AMC boundary condition. In the case of the TM polarization, instead, the AMC boundary condition is effectively achieved by using a material with vanishing permittivity. The role of the permittivity in the three polarizations is discussed. Finally, possible implementations and applications at microwave and optical frequencies are presented.

Originality/value

The idea of using miniaturized inclusions to obtain AMCs is not completely new. However, to the authors' best knowledge, a complete and rigorous theoretical analysis showing the capabilities and the limits of this approach has not yet been presented in the open technical literature.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 32 no. 6
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 11 November 2013

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.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 32 no. 6
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 11 November 2013

Kamil Boratay Alici, Mehmet Deniz Caliskan, Filiberto Bilotti, Alessandro Toscano, Lucio Vegni and Ekmel Ozbay

Metamaterial unit cells composed of deep subwavelength resonators brought up new aspects to the antenna miniaturization problem. The paper experimentally demonstrates a…

Abstract

Purpose

Metamaterial unit cells composed of deep subwavelength resonators brought up new aspects to the antenna miniaturization problem. The paper experimentally demonstrates a metamaterial-inspired miniaturization method for circular patch antennas. In the proposed layouts, the space between the patch and the ground plane is filled with a proper metamaterial composed of either multiple split-ring or spiral resonators (SRs). The authors have manufactured two different patch antennas, achieving an electrical size of λ/3.69 and λ/8.26, respectively. The paper aims to discuss these issues.

Design/methodology/approach

The operation of such a radiative component has been predicted by using a simple theoretical formulation based on the cavity model. The experimental characterization of the antenna has been performed by using a HP8510C vector network analyzer, standard horn antennas, automated rotary stages, coaxial cables with 50 Ω characteristic impedance and absorbers. Before the characterization measurements we performed a full two-port calibration.

Findings

Electrically small circular patch antennas loaded with single layer metamaterials experimentally demonstrated to acceptable figures of merit for applications. The proposed miniaturization technique is potentially promising for antenna applications and the results presented in the paper constitute a relevant proof for the usefulness of the metamaterial concepts in antenna miniaturization problems.

Originality/value

Rigorous experimental characterization of several meta material loaded antennas and proof of principle results were provided.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 32 no. 6
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 11 November 2013

Mirko Barbuto, Andrea Alù, Filiberto Bilotti, Alessandro Toscano and Lucio Vegni

– The purpose of this paper is to present an analytical expression for the characteristic impedance of a microstrip line in presence of a dielectric cover.

Abstract

Purpose

The purpose of this paper is to present an analytical expression for the characteristic impedance of a microstrip line in presence of a dielectric cover.

Design/methodology/approach

Assuming a quasi-TEM propagation mode, a rigorous conformal mapping based on the Schwarz-Christoffel transformation is employed to derive the equivalent capacitance model, which can then be applied to derive a closed analytical expression for the effective permittivity and the characteristic impedance of the line.

Findings

Such a formulation is not limited to the case of a single cover layer, but an arbitrary number of electric overlays can be considered as well. Comparisons with published numerical results and full-wave simulations in the case of a single cover layer have been also performed to test the validity of the proposed approach.

Originality/value

The new analytical formula for the characteristic impedance of a microstrip line with a single dielectric cover shows better performances compared to the one of closed formulas already presented in the literature.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 32 no. 6
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 14 November 2008

Sebastian Emanuel Lauro, Filiberto Bilotti, Alessandro Toscano and Lucio Vegni

To devise a parametric study using a new application of the boundary element method (BEM) and to propose an efficient approach for speeding up the computation time of the…

Abstract

Purpose

To devise a parametric study using a new application of the boundary element method (BEM) and to propose an efficient approach for speeding up the computation time of the BEM based on neural networks (NNs).

Design/methodology/approach

A 3D finite elements formulation is combined with radial basis function NNs to speeding up the computation time.

Findings

The paper shows how to estimate the role of thin slabs filled with unconventional media in order to increase the coupling values when placed between two metallic strips in a coupled microstrip line layout or to improve the shielding properties when used as absorber.

Research limitations/implications

The numerical results here presented are not bianisotropic but can be easily extended to take into account bianisotropic media.

Originality/value

The formulation is one of the only with the potential for investigating unconventional bianisotropic media like Chiral materials which are seen as one possible route to achieving double negative media.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 27 no. 6
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 1 July 2014

Michela Goffredo, Maurizio Schmid, Silvia Conforto, Filiberto Bilotti, Claudio Palma, Lucio Vegni and Tommaso D’Alessio

A novel model of the upper arm under transcutaneous electrical stimulation with multi-pad electrodes is presented and experimentally validated. The model aims at…

Abstract

Purpose

A novel model of the upper arm under transcutaneous electrical stimulation with multi-pad electrodes is presented and experimentally validated. The model aims at simulating and analysing the effects of surface electrical stimulation on biceps brachii. The paper aims to discuss these issues.

Design/methodology/approach

Both the passive properties of tissues surrounding nerve bundles and the active characteristics of the nervous system are included. The output of the proposed model is nerve recruitment and muscle contraction.

Findings

Simulations and experimental tests on six healthy young adults have been conducted and results show that the proposed model gives information on electrically elicited muscle contraction in accordance with in-vivo tests and literature on motor unit recruitment order. Tests with different electrodes configurations show that the spatial distribution of active electrodes is a critical factor in electrically elicited muscle contractions, and that multi-pad electrodes can optimise the stimulation effectiveness and patient comfort with sequences of biphasic pulses of 350 μs at 30 pulses/s and threshold values of 2 mA.

Originality/value

Results encourage the use of the proposed model of the upper arm as a valid and viable solution for predicting the behaviour of the neuromuscular system when surface electrical stimulation is applied, thus optimising the design of neuroprosthetics.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 33 no. 4
Type: Research Article
ISSN: 0332-1649

Keywords

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