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Firenze, Italy

Mencagli M.,University of Siena | Martini E.,University of Siena | Martini E.,Wave Up Srl | Maci S.,University of Siena
IEEE Transactions on Antennas and Propagation | Year: 2015

This paper presents an effective approach for the derivation of the two-dimensional (2-D) frequency-wavenumber dispersion surface of anisotropic metasurfaces (MTSs) consisting of elliptical patches printed over a grounded slab. These MTSs are important in the design of leaky-wave antennas and transformation optics (TO) surface-wave based devices. The formulation resorts to an analytical expression of the currents excited on the element of the periodic texture to define a reduced spectral method of moments (MoM) procedure with only three basis functions. An exact compact formula, which links the MoM matrix to the homogenized equivalent anisotropic impedance of the MTS, is derived. The formulation presented here has been found accurate and useful for designing MTS antennas and TO devices. © 2015 IEEE. Source


Mencagli M.,University of Siena | Martini E.,University of Siena | Martini E.,Wave Up Srl | Gonzalez-Ovejero D.,University of Siena | Maci S.,University of Siena
IEEE Antennas and Wireless Propagation Letters | Year: 2014

Transformation electromagnetics has been extended to design modulated anisotropic metasurfaces (MTSs) able to control the propagation path of surface waves (SWs). The proposed methodology consists in simple formulas that link the parameters of the transformation to the local SW wave-vector. The space-dependent wave-vector distribution is eventually implemented by subwavelength patches printed on a grounded slab. New MTS devices are presented based on these formulas. © 2014 IEEE. Source


Mencagli M.,University of Siena | Martini E.,University of Siena | Martini E.,Wave Up Srl | Maci S.,University of Siena
IEEE Transactions on Antennas and Propagation | Year: 2016

Metasurfaces are thin metamaterials used for manipulating propagation of plane waves and surface-waves (SWs). They can be characterized by homogenized- oundary conditions, which, in absence of losses, can be represented through an equivalent reactance. In this paper, we introduce a general representation of isotropic frequency-dependent reactance which is valid along the dispersion curve of the relevant TM SW. This representation is written in terms of a transition function derived from a manipulation of the Cardano's formula for third-degree algebraic equations. Throughout a large portion of the dispersion curve, this transition function depends on one parameter only, which is an equivalent quasi-static capacitance. Approaching the Floquet-Bloch region, where many higher order Floquet modes are excited, two additional parameters should be extracted from the full-wave data to complete the transitional representation of the reactance until the upper boundary of the Brillouin region. The final formula is valid for a generic isotropic reactance and for an anisotropic reactance when the direction of propagation is along a symmetry axis of the unit cell element. © 2015 IEEE. Source


Gonzalez-Ovejero D.,University of Siena | Martini E.,University of Siena | Martini E.,Wave Up Srl | Vardaxoglou J.,Loughborough University | Maci S.,University of Siena
2015 9th European Conference on Antennas and Propagation, EuCAP 2015 | Year: 2015

This paper investigates the properties of frequency selective metasurfaces (MTSs) made of a layer of conducting elements and a layer of the complementary (aperture) geometry, etched on either side of a dielectric substrate. The elements needed to synthesize such structures are small in terms of the wavelengths comprised within the operating bandwidth. Thus, one obtains improved frequency bandwidth stability and angular response. An interpretation in terms of the MTS's equivalent circuit is provided, along with design guidelines for the proposed structure. © 2015 EurAAP. Source


Minatti G.,European Space Agency | Faenzi M.,University of Siena | Martini E.,University of Siena | Martini E.,Wave Up Srl | And 6 more authors.
IEEE Transactions on Antennas and Propagation | Year: 2015

This paper presents design and analysis methods for planar antennas based on modulated metasurfaces (MTSs). These antennas operate on an interaction between a cylindrical surface-wave (SW) excited by an isotropic TM radiator, and an MTS having a spatially modulated equivalent impedance. The MTS is realized by using sub-wavelength patches printed on a grounded slab, thus resulting in a structure with light weight and compact volume. Both features are appealing characteristics for space applications. This paper introduces for the first time an impedance-based amplitude synthesis of the aperture field distribution and shows several new examples of antennas for space applications obtained in recent research projects financed by the European Space Agency. © 1963-2012 IEEE. Source

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