F. Bilotti

Università Degli Studi Roma Tre, Roma, Latium, Italy

Are you F. Bilotti?

Claim your profile

Publications (197)169.6 Total impact

  • Mirko Barbuto, Filiberto Bilotti, Alessandro Toscano
    [Show abstract] [Hide abstract]
    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; · 1.79 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    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; 6:4416-4425. · 1.08 Impact Factor
  • [Show abstract] [Hide abstract]
    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). · 2.33 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    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 01/2014; 62(8):4220-4229. · 2.33 Impact Factor
  • [Show abstract] [Hide abstract]
    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.
    COMPEL International Journal of Computations and Mathematics in Electrical 11/2013; 32(6). · 0.28 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A new application of a metamaterial-inspired inclusion, i.e. the Split-Ring Resonator (SRR), combined with a commercial Ground Penetrating Radar (GPR) is presented. An SRR is embedded within a soil sample and excited by the GPR antenna. Exploiting the resonant properties of the inclusion, the dielectric permittivity of a typical soil is estimated by observing the GPR data. The proposed method turns out to be very quick and the results are in agreement with many findings in the open technical literature. The point of strength of this approach is the combination of GPR technology and metamaterial concepts that leads to a quick and accurate in-situ estimation, i.e. not-destructive, of the dielectric properties of the underground.
    2013 7th International Congress on Advanced Electromagnetic Materials in Microwaves and Optics (METAMATERIALS 2013); 09/2013
  • A. Monti, A. Alu, A. Toscano, F. Bilotti
    [Show abstract] [Hide abstract]
    ABSTRACT: We propose a general procedure to design mantle cloaks able to reduce the scattering of an object for both polarizations at the same frequency. In particular, we analyze the applicability of closed-form formulas available in the literature for the design of planar metasurfaces consisting of rectangular meshes, and validate their applicability in conformal mantle cloaks for cylindrical objects. Furthermore, we propose an easy retrieval procedure useful to refine the initial analytical design and quickly obtain the required surface impedance of the metasurface for both polarizations. Practical examples of dual-polarization mantle cloaks are presented and discussed.
    2013 7th International Congress on Advanced Electromagnetic Materials in Microwaves and Optics (METAMATERIALS 2013); 09/2013
  • M. Barbuto, F. Bilotti, A. Toscano
    2013 7th International Congress on Advanced Electromagnetic Materials in Microwaves and Optics (METAMATERIALS 2013); 09/2013
  • Source
    M. Manzini, A. Alu, F. Bilotti, L. Vegni
  • [Show abstract] [Hide abstract]
    ABSTRACT: We propose a fast and effective method for estimating the dielectric permittivity of pavement materials. The method is based on a transmission-line analytical model of the ground and on the use of a commercial ground penetrating radar (GPR) system. In order to verify its reliability and effectiveness, we apply the method for retrieving material permittivity of an actual airport taxiway pavement. We estimate the permittivity comparing the measured GPR received signal and the analytical one. The correct permittivity values are found by imposing the maximum correlation between the measured GPR signal and the analytical one.
    2013 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting; 07/2013
  • Mirko Barbuto, Alessandro Toscano, Filiberto Bilotti
    [Show abstract] [Hide abstract]
    ABSTRACT: We investigate on the possibility to generate an electromagnetic field with a non-zero orbital angular momentum (OAM) using a single patch antenna. First, we report an analytical study of a circular patch antenna in order to show that a circular polarized TMnm mode generates an OAM of order n - 1. Then, we design an elliptical patch antenna that radiates a circular polarized electromagnetic field with OAM of the first order. The analysis of the proposed antenna is supported by a proper set of full-wave numerical simulations.
    2013 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting; 07/2013
  • [Show abstract] [Hide abstract]
    ABSTRACT: We propose a flat metamaterial-based lens to be applied to the aperture of a shortened horn antenna in order to achieve gain performances similar to the ones of the corresponding optimum horn over a broad frequency range. In order to achieve an uniform phase distribution at the horn aperture and maximizing, thus, the gain, the central part of the lens consists of a conventional epsilon-positive material and the part closest to the metallic edges of the horn consists of an epsilon-near-zero material, i.e. a wire-medium. Due to the different phase delay of the field at the edges of the aperture on the E- and H-plane, two different wire-mediums are properly designed in order to compensate the phase delay on both planes and achieve the highest possible gain enhancement . As an example, we report the design of the proposed lens for a C-band pyramidal horn. The length of the horn is half the length of the optimum horn, while the obtained gain performances are similar to the ones of the optimal horn over the entire mono-modal frequency band of operation of the feeding waveguide. This result may open the door to several interesting applications in satellite and radar systems.
    2013 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting; 07/2013
  • [Show abstract] [Hide abstract]
    ABSTRACT: We present the design of a flat lens, made by a conventional material and an epsilon near-zero metamaterial, to plug up the aperture of a short horn antenna, in order to achieve radiation performances similar to the ones of the corresponding optimum horn over a broad frequency range. Lens operation is based on the phase-compensation concept: phase-fronts of the field propagating along the short flare of the horn propagate with different phase velocities in the two lens materials, resulting in an uniform phase distribution on the aperture. Starting from the theoretical study of the transmission properties of a bulk epsilon near-zero slab, we derive the analytical formulas for the design of the flat lens and validate them through full-wave numerical simulations. Then, a realistic version of the lens, realized with a wire-medium and exhibiting a near-zero real part of the effective permittivity in the frequency range of interest, is presented. Considering two examples working in the C-band, we show that the lens can be designed for both conical and pyramidal horn antennas. In both cases, the length of the horns is half the one of the corresponding optimum versions, while the obtained radiation performances are similar to those of the optimum horns over a broad frequency band. This result may open the door to several interesting applications in satellite and radar systems.
    IEEE Transactions on Antennas and Propagation 06/2013; 61(6):2929-2937. · 2.33 Impact Factor
  • Source
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, we investigate on the use of non-Foster active elements to increase the operation bandwidth of a split-ring resonator (SRR) for possible application in metamaterial-inspired components. First, we design the circuit topology of the active load required to compensate the intrinsic reactance of the SRR and get a broadband response. Then, we show that the same procedure can be successfully applied to the case of a SRR-based monopole antenna and, in principle, to any metamaterial-inspired device employing SRRs. Finally, integrating an electromagnetic and a circuit simulator, we propose a possible realistic implementation of the active load, based on the employment of commercially available circuit elements. The obtained results (seven times improvement of the impedance bandwidth of the SRR-based monopole antenna) prove that non-Foster active loads can be successfully used to overcome the inherent narrow-band operation of SRR-based passive metamaterials and metamaterial-inspired components. The implementation issues related to circuit element dispersion, parasitic effects, and stability of the active circuit are fully considered in the proposed design.
    IEEE Transactions on Antennas and Propagation 03/2013; 61(3):1219-1227. · 2.33 Impact Factor
  • [Show abstract] [Hide abstract]
    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.
    COMPEL International Journal of Computations and Mathematics in Electrical 01/2013; 32(6). · 0.28 Impact Factor
  • [Show abstract] [Hide abstract]
    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 ?/3.69 and ?/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 O 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.
    COMPEL International Journal of Computations and Mathematics in Electrical 01/2013; 32(6). · 0.28 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Recently, our group has proposed a self-filtering linearly polarized horn antenna that can be used to reduce the noise captured by regular horn feeds. However, the approach used in that design is inherently limited to linear polarization, while possible interesting applications are likely in satellite receiving systems, which are typically based on circularly polarized signals. In this letter, we propose a new approach to obtain a filtering horn antenna working in circular polarization. The proposed solution is based on the design of a linear-to-circular polarization transformer that consists of a complementary electrically small resonator etched on a metallic screen. We first show that this component is able to transform the linear polarization of a regular rectangular waveguide working on the fundamental mode into a circular one. Then, integrating this polarization transformer in a conical horn, we show how it is possible to obtain a circularly polarized filtering horn antenna. The numerical simulations and the measurements performed on a prototype prove that the proposed structure can be effectively used to design a bandpass filtering horn antenna for circularly polarized signals.
    IEEE Antennas and Wireless Propagation Letters 01/2013; 12:1065-1068. · 1.67 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this contribution, we present the design of efficient electrically small apertures loaded with metamaterial-inspired sub-wavelength resonators. The employment of omega and modified protractor resonators enables efficient radiation and automatic impedance matching, without increasing the physical dimensions of the aperture. This phenomenon is applied to the design of several microwave components, some of which are presented in the paper: a. linearly-polarized open-ended waveguides and horn antennas and b. linear-to-circular polarization transformers. The results are supported by proper numerical simulations and measurements.
    Antennas and Propagation (EuCAP), 2013 7th European Conference on; 01/2013
  • [Show abstract] [Hide abstract]
    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.
    COMPEL International Journal of Computations and Mathematics in Electrical 01/2013; 32(6). · 0.28 Impact Factor

Publication Stats

921 Citations
169.60 Total Impact Points

Institutions

  • 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
  • 2007–2010
    • Bilkent University
      • Department of Physics
      Ankara, Ankara, Turkey
  • 2009
    • University of Texas at Austin
      • Department of Electrical & Computer Engineering
      Austin, Texas, United States
  • 2005–2007
    • University of Pennsylvania
      • Department of Electrical and Systems Engineering
      Philadelphia, PA, United States
  • 2003–2005
    • University of Texas at Brownsville and Texas Southmost College
      Brownsville, Texas, United States
  • 2000–2005
    • The American University of Rome
      Roma, Latium, Italy