Search

In this letter, we propose the design of a nano-circuit reactive artificial screen for the synthesis of a given field pattern with sub-wavelength features at visible frequencies. The meta-screen consists of a discrete set of dielectric cells, behaving as lumped reactive elements. The cells have been designed according to the recently proposed new concept of metactronics. The spatial distribution of the cells, and the inter-element electrically small spacing enables the focalization of a sub-wavelength spot beyond the diffraction limit at a prescribed focal distance. The design is supported by full-wave simulations, showing the actual focusing properties of the artificial screen proposed. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2718–2721, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24719

We analyze here the performance of μ-negative metamaterials in different configurations at microwave and optical frequencies that employ variable values of capacitances or tunable varactors, with the purpose of increasing their bandwidth of operation. The proposed method shows moderately good results both in resonant-like and in transmission-line configurations. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 55–59, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22036

The optimized design of patch antennas with inhomogeneous loading materials is presented in this paper. The analysis and a first coarse design of the antennas is applied to a numerical tool based on the method of moments (MoM) and on a full-wave formulation developed in the spectral domain that exploits both rigorous and asymptotic closed-form expressions of the Green's function for a stratified integrated structure with inhomogeneous substrates. In order to match the specific prescribed requirements for the antennas, then, the optimization of the patch shape (fine design) is performed by a dedicated subroutine implementing the genetic algorithm (GA) search and integrated in the aforementioned MoM numerical tool. Some numerical results showing the capabilities of the code are finally presented. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 464–468, 2003

The radiating features of capacitive and inductive impedance surfaces are investigated in this paper. The analysis is particularly devoted to integrated structures with reactive ground planes and is performed through a full-wave Green's function approach in the spectral domain. Some numerical examples, obtained by exploiting such a rigorous formulation, are also presented to illustrate the radiating behaviour of infinitesimal horizontal printed dipoles mounted on reactively loaded integrated structures. It is shown in detail that capacitive surfaces are more suitable than inductive ones for integrated antenna applications, due to both their effectiveness in enhancing the radiation intensity in presence of very thin substrates and their capability of maintaining good radiating performances over a wide frequency range. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 117–121, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11144

A numerical analysis of a uniform rectangular waveguide filled by an inhomogeneous dielectric with a continuous spatial variation of the relative permittivity is presented in this Letter. The proposed method, based on a method-of-moments (MoM) solution of the differential equations for TE, LSE, and LSM modes, is applied to find out the cutoff frequencies of the waveguide. Some numerical examples are also presented, considering both continuous and stepped variations of the permittivity along a transverse direction. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 313–316, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10446

The analysis of patch antennas loaded by general inhomogeneous and lossy chiral media is presented in this paper, implementing a new method-of-lines (MoL) procedure, which considers inhomogeneous planar structures loaded by any bi-isotropic material. Presented results refer to the effect of a chiral cover on the resonance frequency of a simple squared-patch structure. Design charts are presented to simply analyze the separate effects of cover thickness and chirality. © 2002 John Wiley & Sons, Inc. Microwave Opt Technol Lett 32: 143–145, 2002.

In this paper, the analysis of patch antennas with U-shaped metalization loaded by bianisotropic media is developed. A theoretical study is performed to obtain transmission-line equations for bianisotropic materials, and then a method-of-lines (MoL) procedure is applied to obtain the radiative characteristics. Presented results assure, for particular patch dimensions and feed application geometry, a multifrequency operation in the microwave range, even for isotropic substrates. The application of bianisotropic materials gives better performances for bandwidth and input impedance at the central frequency, but degrades other frequency operation performances. © 2002 John Wiley & Sons, Inc. Microwave Opt Technol Lett 32: 3–5, 2002.