Research Activity - Revision history

Apolemi: /* TOPICS */

2010-06-23T01:50:48Z

TOPICS

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	= TOPICS <br> =		= TOPICS <br> =
	My research activity begins at the Department of Information Engineering of the University of Siena, mainly oriented to the asymptotic study of the Green’s function associated with truncated periodic arrays of elementary sources embedded in multilayered environment. This activity has been pursed in collaboration with Prof. Felsen (University of Boston). Contemporarily, my scientific activity has also investigated analytical and numerical methods in electromagnetism, for the prediction of the electromagnetic scattering frm large objects, with Prof. Roberto Tiberio and Prof. Stefano Maci as supervisors. The research activity has also been developed in the framework of national research programs (PRIN), university research programs (PAR), and in the framework of projects financed by the Italian Space Agency (ASI). I ~~also~~ also participated to European research programs, as ACE and EAML.		My research activity begins at the Department of Information Engineering of the University of Siena, mainly oriented to the asymptotic study of the Green’s function associated with truncated periodic arrays of elementary sources embedded in multilayered environment. This activity has been pursed in collaboration with Prof. Felsen (University of Boston). Contemporarily, my scientific activity has also investigated analytical and numerical methods in electromagnetism, for the prediction of the electromagnetic scattering frm large objects, with Prof. Roberto Tiberio and Prof. Stefano Maci as supervisors. The research activity has also been developed in the framework of national research programs (PRIN), university research programs (PAR), and in the framework of projects financed by the Italian Space Agency (ASI). I also participated to European research programs, as ACE and EAML.

	The experience on periodic structures and on Green's function for multilayered structures has allowed me to start a fruitful collaboration with Politecnico di Torino, to arrange new and efficient tools for the analysis of aperiodic and periodic printed elements embedded in dielectric materials. Also, my interests have been focused on lens antennas, for which I am involved in a European Research Networking Program (RNP) with University of Rennes, Radio Frequency IDentification systems, and on microwave radiometers for fire detection.		The experience on periodic structures and on Green's function for multilayered structures has allowed me to start a fruitful collaboration with Politecnico di Torino, to arrange new and efficient tools for the analysis of aperiodic and periodic printed elements embedded in dielectric materials. Also, my interests have been focused on lens antennas, for which I am involved in a European Research Networking Program (RNP) with University of Rennes, Radio Frequency IDentification systems, and on microwave radiometers for fire detection.

Apolemi: /* TOPICS */

2010-06-23T01:50:27Z

TOPICS

← Older revision		Revision as of 01:50, 23 June 2010
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	= TOPICS <br> =		= TOPICS <br> =
			My research activity begins at the Department of Information Engineering of the University of Siena, mainly oriented to the asymptotic study of the Green’s function associated with truncated periodic arrays of elementary sources embedded in multilayered environment. This activity has been pursed in collaboration with Prof. Felsen (University of Boston). Contemporarily, my scientific activity has also investigated analytical and numerical methods in electromagnetism, for the prediction of the electromagnetic scattering frm large objects, with Prof. Roberto Tiberio and Prof. Stefano Maci as supervisors. The research activity has also been developed in the framework of national research programs (PRIN), university research programs (PAR), and in the framework of projects financed by the Italian Space Agency (ASI). I also also participated to European research programs, as ACE and EAML.

	The Alessia Polemi research activity begins at the Department of Information Engineering of the University of Siena, in the period of preparation of the master thesis degree, oriented to the asymptotic study of the Green’s function associated with truncated periodic arrays of elementary sources embedded in multilayered environment. This activity continued after the master thesis degree in cooperation with Prof. Felsen from the University of Boston, and it produced the publication of a sequence of three papers on this subject. Contemporarily, the scientific activity of Alessia Polemi also investigated the field of electromagnetic analytical and numerical methods, particularly referring to the high frequency techniques for the prediction of the electromagnetic scattering, with Prof. Roberto Tiberio and Prof. Stefano Maci as supervisors. The research activity has also been developed in the framework of national research programs (PRIN), university research programs (PAR), and in the framework of projects financed by the Italian Space Agency (ASI). She also participates to European research programs, as ACE and EAML. The experience on periodic structures and on Green's function for multilayered structures allowed ~~her~~ to start a fruitful collaboration with Politecnico di Torino, to ~~assest~~ new and efficient tools for the analysis of aperiodic and periodic printed elements embedded in dielectric materials. ~~The collaboration with Politecnico di Torino has~~ been ~~also addressed to the problem of kernel regularization in 3D singular integral equations. Recently, her research activity is focusing~~ on lens ~~antenna~~, for which ~~she is~~ involved in a European Research Networking Program (RNP) with University of Rennes, ~~on RFID antenna design~~, on microwave radiometers, ~~and~~ on ~~metamaterials and plasmonic structure at optical frequencies~~, ~~on which she is undertaking an international~~ collaboration with Prof. Nader Engheta (University of Pennsylvania) and Prof. Andrea Alù (University of Austin, ~~Texas)~~.		The experience on periodic structures and on Green's function for multilayered structures has allowed me to start a fruitful collaboration with Politecnico di Torino, to arrange new and efficient tools for the analysis of aperiodic and periodic printed elements embedded in dielectric materials. Also, my interests have been focused on lens antennas, for which I am involved in a European Research Networking Program (RNP) with University of Rennes, Radio Frequency IDentification systems, and on microwave radiometers for fire detection.

			I’m currently involved in a European working group (lead by Prof. Per-Simon Kildal from Chalmers Univeristy of Technology) focused on the investigation of new generations of waveguides, to be employed in the higher region of the microwave spectrum. In this working group, I developed analytical models to describe the dispersion characteristic of metallic waveguides based on periodic stop band surfaces.

			Recently, in the framework of a collaboration with Prof. Nader Engheta (University of Pennsylvania) and Prof. Andrea Alù (University of Texas at Austin), I started to work on metamaterials and plasmonic structure at optical frequencies, with particular interest towards plasmonic channels and nanocircuits. My interest concerns specifically the numerical and analytical description of the dispersion characteristic of plasmonic waveguides, together with the possibility to load them with nanoparticles, which act as nanoinductors and nanocapacitors.

			Also, within the collaboration with Prof. Kevin Shuford at the Drexel University, I recently started to work on the interaction between nanoparticles and molecules, providing both analytical and numerical support to the investigation the spectra of assembled nanoparticles, with particular interest to periodic SERS nanosurface.
	<br><br><br><br>		<br><br><br><br>

Apolemi: /* ASYMPTOTIC METHODS FOR ARRAY ANTENNAS */

2010-06-23T01:46:58Z

ASYMPTOTIC METHODS FOR ARRAY ANTENNAS

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	== ASYMPTOTIC METHODS FOR ARRAY ANTENNAS<br> ==		== ASYMPTOTIC METHODS FOR ARRAY ANTENNAS<br> ==
	The research activity in this area ~~has the objective~~ the development and application of asymptotic methods for analysis and design of array antennas embedded in multilayered dielectric environment. In particular, the research is mainly dedicated to the characterization of diffraction phenomena, generated by the periodicity truncation (semi-infinite array, sectoral array) through the array Green’s function (AGF), and through the subsequent integration of the representation into full-wave codes for the efficient analysis of printed antennas. <br>		The research activity in this area is focused on the development and application of asymptotic methods for analysis and design of array antennas embedded in multilayered dielectric environment. In particular, the research is mainly dedicated to the characterization of diffraction phenomena, generated by the periodicity truncation (semi-infinite array, sectoral array) through the array Green’s function (AGF), and through the subsequent integration of the representation into full-wave codes for the efficient analysis of printed antennas. <br>

Apolemi: /* Hollow Core Fibre for THz Applications */

2010-06-19T00:15:50Z

Hollow Core Fibre for THz Applications

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	Hollow Core Photonic Band Gap Fibres (HC-PBGFs) are investigated in order to obtain low loss wave guiding and good aperture field distribution in the terahertz region (0.1 − 10THz) of the electromagnetic spectrum. Waveguides and antennas design		Hollow Core Photonic Band Gap Fibres (HC-PBGFs) are investigated in order to obtain low loss wave guiding and good aperture field distribution in the terahertz region (0.1 − 10THz) of the electromagnetic spectrum. Waveguides and antennas design
	in this spectral region is a major challenge due to the high conductivity losses of metals and high absorption of dielectrics. Numerical results show the possibility to reach propagation loss two decades lower than the bulk absorption losses of the material used to fabricate the fibre, over a wide range of wavelength. The purity of the aperture field distribution at the		in this spectral region is a major challenge due to the high conductivity losses of metals and high absorption of dielectrics. Numerical results show the possibility to reach propagation loss two decades lower than the bulk absorption losses of the material used to fabricate the fibre, over a wide range of wavelength. The purity of the aperture field distribution at the
	HC-PBGF section suggests a possible employment of such a structure as aperture antenna, for possible feed systems in THz applications [C26].		HC-PBGF section suggests a possible employment of such a structure as aperture antenna, for possible feed systems in THz applications [C26][C28].

	[[File:fibre.png\|400px]]<br>		[[File:fibre.png\|400px]]<br>

Apolemi: /* PUBLICATIONS */

2009-11-15T20:11:51Z

PUBLICATIONS

← Older revision		Revision as of 20:11, 15 November 2009
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	=PUBLICATIONS<br>=		=PUBLICATIONS<br>=
	[http://www.dii.unimo.it/wiki/index.php/~~My_Publications~~ Publications]		[http://www.dii.unimo.it/wiki/index.php/My_publications Publications]

Apolemi: /* PUBLICATIONS */

2009-11-15T20:11:27Z

PUBLICATIONS

← Older revision		Revision as of 20:11, 15 November 2009
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	=PUBLICATIONS<br>=		=PUBLICATIONS<br>=
	[http://www.dii.unimo.it/wiki/index.php/~~My_publications~~ Publications]		[http://www.dii.unimo.it/wiki/index.php/My_Publications Publications]

Apolemi: /* Ridge gap Waveguides */

2009-08-25T14:11:00Z

Ridge gap Waveguides

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	== ONGOING ACTIVITIES<br> ==		== ONGOING ACTIVITIES<br> ==
	===Ridge gap Waveguides===		===Ridge gap Waveguides===
	This activity is on the attempt to elaborate an approximate analytical analysis of the quasi-TEM dominant mode in a parallel plate metamaterial-based waveguide. This waveguide is constituted by a bed of nails surface interrupted by a metal strip, and covered by a metallic plate. This structure is simple to manufacture, especially at millimetre and sub-millimetre wave frequencies [C25].		This activity is on the attempt to elaborate an approximate analytical analysis of the quasi-TEM dominant mode in a parallel plate metamaterial-based waveguide. This waveguide is constituted by a bed of nails surface interrupted by a metal strip, and covered by a metallic plate. This structure is simple to manufacture, especially at millimetre and sub-millimetre wave frequencies [C25][R13].

	[[File:gap.png\|400px]]<br>		[[File:gap.png\|400px]]<br>

Apolemi: /* Extension of Incremental Theory of Diffraction for analysis of scattering from planar canonical structures */

2009-07-28T13:16:56Z

Extension of Incremental Theory of Diffraction for analysis of scattering from planar canonical structures

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	===Extension of Incremental Theory of Diffraction for analysis of scattering from planar canonical structures===		===Extension of Incremental Theory of Diffraction for analysis of scattering from planar canonical structures===
	The applicability of the Incremental Theory of Diffraction (ITD), tipically limited to the scattering from metallic surfaces, has been extended to non perfectly conducting surfaces (alse dielectric). The ITD is based on a suitable use of canonical problem solutions which locally approximate the structure geometry. A localization process allows to define incremental coefficients which, integrated along discontinuity lines or shadow lines, furnish the diffracted field[R3]. The main objective has been the derivation of a heuristic ITD formulation, simple but still accurate for most of engineering applications, starting from the rigorous formulation for metallic screens, with reference to the canonical problem associated with half-plane and two-parts junction [C13][C17][C18][C21][C30]. The so derived incremental diffraction coefficient is ~~implicetely~~ reciprocal and reduces to the ITD coefficient for conducting faces wedges (pec or pmc), in limiting cases. Through this formulation has been treated the scattering from faceted structures formed by composite materials, also in caustic zones, where the UTD ray-description becomes singular. In addiction, the ITD diffraction coefficient has also been written in terms of "fringe" contribution, in order to be inserted in already available PO codes.		The applicability of the Incremental Theory of Diffraction (ITD), tipically limited to the scattering from metallic surfaces, has been extended to non perfectly conducting surfaces (alse dielectric). The ITD is based on a suitable use of canonical problem solutions which locally approximate the structure geometry. A localization process allows to define incremental coefficients which, integrated along discontinuity lines or shadow lines, furnish the diffracted field[R3]. The main objective has been the derivation of a heuristic ITD formulation, simple but still accurate for most of engineering applications, starting from the rigorous formulation for metallic screens, with reference to the canonical problem associated with half-plane and two-parts junction [C13][C17][C18][C21][C30]. The so derived incremental diffraction coefficient is implicitly reciprocal and reduces to the ITD coefficient for conducting faces wedges (pec or pmc), in limiting cases. Through this formulation has been treated the scattering from faceted structures formed by composite materials, also in caustic zones, where the UTD ray-description becomes singular. In addiction, the ITD diffraction coefficient has also been written in terms of "fringe" contribution, in order to be inserted in already available PO codes.

	[[File: ITD.png\|500px]]<br>		[[File: ITD.png\|500px]]<br>

Apolemi: /* Extension of Incremental Theory of Diffraction for analysis of scattering from planar canonical structures */

2009-07-28T13:16:31Z

Extension of Incremental Theory of Diffraction for analysis of scattering from planar canonical structures

← Older revision		Revision as of 13:16, 28 July 2009
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	===Extension of Incremental Theory of Diffraction for analysis of scattering from planar canonical structures===		===Extension of Incremental Theory of Diffraction for analysis of scattering from planar canonical structures===
	The applicability of the Incremental Theory of Diffraction (ITD), tipically limited to the scattering from metallic surfaces, has been extended to non perfectly conducting surfaces (alse dielectric). The ITD is based on a suitable use of canonical problem solutions which locally approximate the structure geometry. A localization process allows to define incremental coefficients which, integrated along discontinuity lines or shadow lines, furnish the diffracted field[R3]. The main objective has been the derivation of a ~~heuristc~~ ITD formulation, simple but still accurate for most of engineering applications, starting from the rigorous formulation for metallic screens, with reference to the canonical problem associated with half-plane and two-parts junction [C13][C17][C18][C21][C30]. The so derived incremental diffraction coefficient is implicetely reciprocal and reduces to the ITD coefficient for conducting faces wedges (pec or pmc), in limiting cases. Through this formulation has been treated the scattering from faceted structures formed by composite materials, also in caustic zones, where the UTD ray-description becomes singular. In addiction, the ITD diffraction coefficient has also been written in terms of "fringe" contribution, in order to be inserted in already available PO codes.		The applicability of the Incremental Theory of Diffraction (ITD), tipically limited to the scattering from metallic surfaces, has been extended to non perfectly conducting surfaces (alse dielectric). The ITD is based on a suitable use of canonical problem solutions which locally approximate the structure geometry. A localization process allows to define incremental coefficients which, integrated along discontinuity lines or shadow lines, furnish the diffracted field[R3]. The main objective has been the derivation of a heuristic ITD formulation, simple but still accurate for most of engineering applications, starting from the rigorous formulation for metallic screens, with reference to the canonical problem associated with half-plane and two-parts junction [C13][C17][C18][C21][C30]. The so derived incremental diffraction coefficient is implicetely reciprocal and reduces to the ITD coefficient for conducting faces wedges (pec or pmc), in limiting cases. Through this formulation has been treated the scattering from faceted structures formed by composite materials, also in caustic zones, where the UTD ray-description becomes singular. In addiction, the ITD diffraction coefficient has also been written in terms of "fringe" contribution, in order to be inserted in already available PO codes.

	[[File: ITD.png\|500px]]<br>		[[File: ITD.png\|500px]]<br>

Apolemi: /* Numerical models */

2009-07-28T13:15:29Z

Numerical models

← Older revision		Revision as of 13:15, 28 July 2009
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	=== Numerical models ===		=== Numerical models ===
	In the case when the radiating element is embedded into multilayered dielectric structures, the Green’s function calculation even in the spectral domain is more complex, and the integral relevant to the Fourier transformation is typically solved numerically. Nevertheless, this integral shows some difficulties related to the presence of poles associated with surface and leaky waves, and to its oscillating ~~behaviour~~. In this context, more effort has been devoted to the choice of alternative integrations paths and integration techniques which can improve the efficiency of numerical codes [RT1]. To accelerate the Green’s function calculation even in the near zone where the asymptotic technique fail, the research activity has regarded the implementation of numerical codes based on approximations known in literature as complex images , which allow the representation of the Green’s function in terms of a few spherical sources, whose ray can be complex. Particular attention has been given to improve the convergence of these methods, with the scope to be inserted into a MoM code for the analysis of printed antennas, already developed in co-operation with Politecnico of Turin, and up to now based standard integration techniques [RT4][RT5]. The convergence has been improved by properly extracting dominant contributions of the Green’s function, related to the quasi-static term, and to the guided waves. This approach is particularly efficient in the near zone, where other techniques, as the asymptotic one, fail.		In the case when the radiating element is embedded into multilayered dielectric structures, the Green’s function calculation even in the spectral domain is more complex, and the integral relevant to the Fourier transformation is typically solved numerically. Nevertheless, this integral shows some difficulties related to the presence of poles associated with surface and leaky waves, and to its oscillating behavior. In this context, more effort has been devoted to the choice of alternative integrations paths and integration techniques which can improve the efficiency of numerical codes [RT1]. To accelerate the Green’s function calculation even in the near zone where the asymptotic technique fail, the research activity has regarded the implementation of numerical codes based on approximations known in literature as complex images , which allow the representation of the Green’s function in terms of a few spherical sources, whose ray can be complex. Particular attention has been given to improve the convergence of these methods, with the scope to be inserted into a MoM code for the analysis of printed antennas, already developed in co-operation with Politecnico of Turin, and up to now based standard integration techniques [RT4][RT5]. The convergence has been improved by properly extracting dominant contributions of the Green’s function, related to the quasi-static term, and to the guided waves. This approach is particularly efficient in the near zone, where other techniques, as the asymptotic one, fail.