Filiberto Bilotti

Università Degli Studi Roma Tre, Roma, Latium, Italy

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Publications (214)176.73 Total impact

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    ABSTRACT: Using two suitably tailored concentric cloaking metasurfaces, we demonstrate several interesting features of these covers, including significant broadband and/or dual-band scattering reduction. We also show that nearly perfect cloaking for moderately sized targets is enabled by complementary bilayer pairings. We apply these concepts to realistic bilayer cloaks covering a finite-length conductive rod for multiband and wideband operation, offering a $>5-text{dB}$ (70%) scattering suppression over bandwidths that exceed any passive mantle cloak demonstrated so far by over nine times. Finally, we apply the same covers to more complex geometries, showing that moderate scattering suppression is maintained, despite the change in geometry and increased size.
    IEEE Transactions on Antennas and Propagation 07/2015; 63(7):1-1. DOI:10.1109/TAP.2015.2421951 · 2.18 Impact Factor
  • Alessio Monti · Andrea Alù · Alessandro Toscano · Filiberto Bilotti
    Photonics 06/2015; 2(2):540-552. DOI:10.3390/photonics2020540
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    ABSTRACT: We present the design and realization of anisotropic mantle cloaks operating, at the same frequency, for both TM and TE incident polarizations. Starting from the analytical model of metasurfaces available in the literature, we first explore the potentials and limitations of the most common metasurface geometries for their application as mantle cloaks. Then, we introduce new types of patterned surfaces aimed at improving their polarization response. We demonstrate that, only by using four metasurface topologies, it is possible to obtain all required combinations of positive and negative reactance values in order to design effective mantle cloaks for planar, cylindrical, and three-dimensional (3-D) objects. We also show that the accuracy of the analytical formulas commonly used to design such metasurfaces is not necessarily sufficient for cloaking purposes. Therefore, we introduce and validate a numerical procedure to refine the analytical design and optimize the cloak performance. The effectiveness of the designed covers is checked with full-wave simulations. Finally, some antenna applications of dual-polarized mantle cloaks are proposed and several experimental measurements conducted on fabricated prototypes are also provided.
    IEEE Transactions on Antennas and Propagation 04/2015; 63(4):1775-1788. DOI:10.1109/TAP.2015.2396532 · 2.18 Impact Factor
  • A. Monti · A. Alù · A. Toscano · F. Bilotti
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    ABSTRACT: In this paper, we investigate the application of the mantle cloaking technique to near-infrared and visible frequencies, analyzing and designing thin covers consisting of 2D arrays of plasmonic nanoparticles. First, we validate and generalize an analytical model recently appeared in the literature to describe a 2D array of plasmonic nanoparticles as a metasurface characterized by its homogenized surface reactance. We prove that the proposed model allows to efficiently design 2D mantle cloaks with an assigned surface reactance, enabling, thus, the extension of the mantle cloaking technique to optical frequencies. Then, we design realistic optical mantle cloaks made of 2D arrays of spheroidal plasmonic nanoparticles with a high eccentricity. We show that the proposed cloaks allow significant, moderately broadband cloaking effects at visible frequencies. In our designs, we consider realistic losses and non-critical nanoparticle dimensions to envision a practical realization of the proposed cloaks.
    Journal of Applied Physics 03/2015; 117(12):123103. DOI:10.1063/1.4916257 · 2.18 Impact Factor
  • A. Monti · M. Barbuto · A. Toscano · F. Bilotti
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    ABSTRACT: In this contribution, we propose the use of Non-Foster circuit to dramatically improve the bandwidth of operation of enhanced transmission devices based on the employment of Split-Ring Resonators (SRRs). The idea behind the proposed solution is to compensate the intrinsic reactance of the SRR through a proper non-Foster active load placed across its external gap. The stability analysis and an ideal load circuit working at Very High Frequency (VHF) band are developed and presented.
    AIP Conference Proceedings 03/2015; 1648. DOI:10.1063/1.4912802
  • M. Barbuto · A. Monti · D. Ramaccia · F. Bilotti · A. Toscano
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    ABSTRACT: In this contribution we report the design and the realization procedure of a low-cost and low-weight metamaterial-inspiredelectromagnetic absorber working in the X-band. The proposed device is constituted by a metasurface, properly designed to emulate the behavior of a perfect electromagnetic conductor, and a thin resistive graphite sheet realized with cheap and easy-to-find products. Specific design details as well as the experimental characterization of therealized prototypeare provided.
    AIP Conference Proceedings 03/2015; 1648. DOI:10.1063/1.4912798
  • Mirko Barbuto · Fabrizio Trotta · Filiberto Bilotti · Alessandro Toscano
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    ABSTRACT: In this communication, we present the design of filtering horn antennas with band-stop characteristics obtained through the use of electrically small magnetic resonators. In particular, a split-ring resonator (SRR) etched on a Rogers Duroid RT5870 dielectric substrate is inserted within the metallic flare of the horn at a proper distance from the throat. At around the resonant frequency of the SRR transmission is highly reduced and a single notched-band is obtained. In order to extend the result to dual-band operation, we also present the design of the filtering module made by two SRRs with different dimensions. The validity of the proposed approach is verified through proper sets of full-wave simulations and experiments on fabricated prototypes. The proposed solution is economical, light, electrically small, easily implementable on already existing radiators, and can find application in wideband communication systems affected by narrowband interfering signals.
    IEEE Transactions on Antennas and Propagation 02/2015; 63(2):781-785. DOI:10.1109/TAP.2014.2378269 · 2.18 Impact Factor
  • Mirko Barbuto · Fabrizio Trotta · Filiberto Bilotti · Alessandro Toscano
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    ABSTRACT: Recently, we have presented a novel approach to design metamaterial-inspired notch filters that can be integrated within horn antennas of receiving systems to mitigate the effects of narrowband interfering signals. The filter module consists of a single Split Ring Resonator (SRR), whose rejection band needs to be matched to the bandwidth of the particular interfering signal we want to suppress. Extending our previous work, we show here how it is possible to control the bandwidth of such a filtering module by using different metamaterial-inspired resonators. In particular, we show that, while a reduction of the rejection band can be easily obtained by increasing the miniaturization rate of the resonator, the enlargement of the rejection band cannot be obtained in the same way by simply reducing the resonator quality factor. We show that a solution of the latter problem can be worked out by applying the “critical coupling” concept and considering the filtering module to be made of two equal SRRs with a proper optimal separation. The effectiveness of the approach is demonstrated trough proper full-wave simulations and experiments on a fabricated prototype. The proposed technique, used here to design a filtering module for a specific radiating system, has a more general relevance and can be applied to all cases where the operation bandwidth of a component is limited by the resonant nature of a single metamaterial-inspired particle.
    Progress In Electromagnetics Research C 01/2015; 58:61-68. DOI:10.2528/PIERC15051402 · 1.23 Impact Factor
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    ABSTRACT: In this paper, we propose a new retrieval technique to estimate the dielectric permittivity of the sub-soil materials of a stratified structure. The core of the retrieval procedure is a proper electromagnetic circuit model representing the realistic stratified media as a cascade of transmission line segments. Exploiting the analogies between the electrical parameters of the transmission line segments and the constitutive parameters of the materials of the multilayer structure, the propagation of the Ground Penetrating Radar (GPR) signal is equivalently represented as a pair of voltage and current waves propagating in the transmission line network. The effectiveness of the proposed retrieval technique is confirmed by proper experimental results. In particular, the retrieved electromagnetic parameters of the sub-soil materials are found to be consistent with the ones obtained by a direct characterization of the same materials. These results suggest that the proposed method can be successfully applied to the material characterization able to monitor several macroscopic properties of sub-soil materials.
    Progress In Electromagnetics Research 01/2015; 151:65-72. DOI:10.2528/PIER15022002 · 1.23 Impact Factor
  • Jason Soric · Alessio Monti · Alessandro Toscano · Filiberto Bilotti · Andrea Alu
    IEEE Transactions on Antennas and Propagation 01/2015; DOI:10.1109/TAP.2015.2476468 · 2.18 Impact Factor
  • Giacomo Oliveri · Filiberto Bilotti · Alessandro Toscano · Andrea Massa
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    ABSTRACT: The System-by-Design (SbD) paradigm is adopted in this work in order to synthesize innovative microwave devices comprising task-oriented engineered materials. More in detail, the synthesis problem is formulated in the SbD framework in terms of the combination of a set of elementary functional blocks, each one devoted to the analysis/synthesis of a specific portion of the target device (e.g., the electromagnetic characterization of the material, the simulation of the device comprising the engineered material, the configuration of the material unit cell). The design blocks are then combined in an overall SbD loop to yield an integrated design procedure which is able to fully exploit the degrees of freedom available in the design to satisfy the physical/performance applicative constraints with the minimum costs, andmaximum efficiency and scalability. Representative numerical examples will be reported in the presentation concerning the design of different wave manipulating devices within the proposed SbD approach.
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    ABSTRACT: We discuss the use of metasurfaces and plasmonic metamaterials to minimize the scattering from receiving antennas and sensors, with the goal of maximizing their absorption efficiency. We first analytically study and highlight the potential of these approaches to realize optimized sensors with the desired level of efficiency, being able to minimize the electrical presence of a receiving antenna for a chosen level of overall absorption. Realistic cloak designs, investigated using full-wave simulations, verify the behavior analytically predicted by Mie theory. These optimized cloaks offer a practical way to flexibly tailor the scattering of receiving antennas, with great benefits in the design and optimization of near-field sensors, remote communication systems, spoof targets and improved antenna blockage resiliency. Optimized covers may also provide other interesting features for the same receiving antenna by just tuning its resistive load, such as optimal wireless power harvesting or high-to-low tunable absorption efficiency.
    IEEE Transactions on Antennas and Propagation 08/2014; 62(8):4220-4229. DOI:10.1109/TAP.2014.2322891 · 2.18 Impact Factor
  • Mirko Barbuto · Filiberto Bilotti · Alessandro Toscano
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    ABSTRACT: In this paper, we present a new class of waveguide components based on the use of complementary electrically small resonators etched on metallic sheets. We first show a rectangular-to-circular waveguide transition that allows to effectively match waveguides with different cross-sections and to transform the linearly polarized TE10-mode of a rectangular waveguide into a circularly polarized TE11-mode of a circular waveguide. Then, using similar structures, we present the design and the numerical results of two power dividers and of an orthomode transducer. All these components, employing only thin metallic sheets with properly shaped slits, can be integrated in waveguide transmission systems without increasing their space occupancy. A proper set of full-wave numerical simulations proves the validity of the proposed approach
    Photonics and Nanostructures - Fundamentals and Applications 08/2014; 12(4). DOI:10.1016/j.photonics.2014.03.005 · 1.47 Impact Factor
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    ABSTRACT: This contribution aims at investigating the possibility to cloak a spherical object from an acoustic wave by applying the scattering cancellation approach. In electromagnetism, the scattering problem is treated using the Mie expansion technique, through which the scattered field by a spherical object can be represented as a superposition of TE and TM spherical harmonics. It is possible to extend this concept to the acoustic field by defining an analogous approach; the pressure field, generated by an elastic wave impinging on a spherical object, can be expressed applying the Mie expansion technique, as well. In acoustics, to achieve scattering suppression at a given frequency, the constitutive parameters to control are density and compressibility. By varying these parameter values, it is possible to define an engineered material with anomalous properties, which cannot be found in nature, able to reduce the scattering cross-section (SCS) from a spherical object. We propose a study about the effectiveness of the SCS reduction from an elastic sphere coated with a properly-designed acoustic metamaterial. The sensitivity of the SCS to parameter variations is analyzed for different coating thicknesses and sphere dimensions. Our analysis is supported by both the analytical modelling of the structure and numerical simulations.
    Sustainability 07/2014; 6(7):4416-4425. DOI:10.3390/su6074416 · 0.94 Impact Factor
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    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 mu s 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.
    COMPEL International Journal of Computations and Mathematics in Electrical 07/2014; 33(4). DOI:10.1108/COMPEL-04-2013-0118 · 0.37 Impact Factor
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    ABSTRACT: In this paper, we present a new analytical model of the connected bi-omega structure consisting of two bi-omega particles connected together through their arms. A single bi-omega particle consists of a pair of regular equal omegas with mirror symmetry. Assuming the individual bi-omega particle electrically small, the equivalent circuit is derived, in order to predict its resonant frequency. Then, two bi-omega particles are connected together, obtaining a symmetric structure that supports two fundamental modes, with even and odd symmetries, respectively. The proposed analytical model, then, is used to develop a procedure allowing the design of the particle for a desired resonant frequency. The effectiveness of the proposed analytical model and design guidelines is confirmed by proper comparisons to full-wave numerical and experimental results. We also demonstrate through a proper set of experiments that the resonant frequencies of the connected bi-omega particle depend only on the geometrical and electrical parameters of the omegas and are rather insensitive to the practical scenario where the particle itself is actually used, e.g. in free-space, rectangular waveguide or across an aperture in a metallic screen.
    IEEE Transactions on Antennas and Propagation 03/2014; 62(4). DOI:10.1109/TAP.2014.2301445 · 2.18 Impact Factor
  • Mirko Barbuto · Fabrizio Trotta · Filiberto Bilotti · Alessandro Toscano
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    ABSTRACT: The recent extension of the orbital angular momentum (OAM) concept from optical to microwave frequencies has led some researchers to explore how well established antenna techniques can be used to radiate a non-zero OAM electromagnetic field. In this frame, the aim of the present paper is to propose a new approach to generate a non-zero OAM field through a single patch antenna. Using the cavity model, we first analyze the radiated field by a standard circular patch and show that a circular polarized (CP) TMnm mode excited by using two coaxial cables generates an electromagnetic field with an OAM of order ±(n-1). Then, in order to obtain a simpler structure with a single feed, we design an elliptical patch antenna working on the right-handed (RH) CP TM21 mode. Using full-wave simulations and experiments on a fabricated prototype, we show that the proposed antenna effectively radiates an electromagnetic field with a first order OAM. Such results prove that properly designed patch antennas can be used as compact and low-cost generators of electromagnetic fields carrying OAM.
    Progress In Electromagnetics Research 01/2014; 148:23-30. DOI:10.2528/PIER14050204 · 1.23 Impact Factor
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    01/2014; 1:1. DOI:10.1051/epjam/2014002
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    ABSTRACT: The introduction of electromagnetic (EM) media with unique field manipulation properties, collectively labelled as metamaterials, has boosted the interest toward the design, the fabrication, and the testing of artificial materials whose features can be engineered according to the applicative requirements and user objectives. In this framework, the long-term promise of reconfigurable metamaterial theory (i.e., the possibility to change the EM response of a 2-D/3-D material arbitrarily and in real time) has given the designers an extremely wide number of new degrees of freedom for the synthesis of innovative adaptive systems. Moreover, successful experimental validations of reconfigurable metamaterials in the entire EM spectrum from microwaves to optical frequencies have further stimulated academic and industrial interests in developing devices with enhanced performances, efficiency, and robustness. Nevertheless, the exploitation of reconfigurable metamaterials in commercial devices is still an open problem with several challenges from both the theoretical and technological viewpoints. This paper is then aimed at reviewing the latest advances on reconfigurable metamaterial engineering from the methodological perspective also providing a comprehensive and balanced survey on latest concepts, current trends, and envisaged future developments on this active field of research.
    International Journal of Antennas and Propagation 01/2014; 2014(7):1-2. DOI:10.1155/2014/215394 · 0.66 Impact Factor

Publication Stats

2k Citations
176.73 Total Impact Points


  • 1999–2014
    • Università Degli Studi Roma Tre
      • • Department of Applied Electronics
      • • Department of Electronic Engineering
      Roma, Latium, Italy
  • 2010
    • The University of Arizona
      Tucson, Arizona, United States
  • 2003–2005
    • University of Texas at Brownsville and Texas Southmost College
      Brownsville, Texas, United States
  • 2001–2002
    • The American University of Rome
      Roma, Latium, Italy