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The main objective of this paper is to provide a self-consistent analytical model for the approximate current distribution induced on an arbitrarily loaded wire antenna of moderate length operating in its receiving mode. The results of our analysis shed light on a debated issue regarding the circuit model of a receiving antenna and show that currently available simplified analytical models for receiving dipoles fail to satisfy basic power conservation requirements. These general findings are applied to the proper homogenization of composite materials and surfaces, and to minimum-scattering receivers and absorbers. [ABSTRACT FROM AUTHOR]

We propose the use of metamaterial-inspired ultranarrow channels at cutoff to realize an interesting matching between a coaxial antenna and a waveguide. The anomalous properties of a channel at cutoff, analogous to those of zero permittivity materials, allow a simple matching design, valid for arbitrary waveguides, with large degrees of freedom in terms of geometry, length and possible bending of the connecting channel. Moreover, the static-like properties of the channel allow such matching, independent of the relative position of the antenna and possible bending and abruptions along the channel. [ABSTRACT FROM AUTHOR]

The detailed theory of a single subwavelength conformal radiator that exploits the resonant properties of thin cylindrical metamaterial shells supporting leaky waves is presented. It is shown and reviewed analytically and numerically how a circularly symmetric resonant leaky mode may be supported by a properly designed subwavelength homogenous cylindrical shell of low negative permittivity. Some physical insights are provided and numerical simulations with a feed point, considering also the finiteness of the antenna in the longitudinal direction, are presented and discussed. Moreover, possibilities and limitations of a practical realization of this setup are mentioned, considering in details the possible anisotropies in the metamaterials. [ABSTRACT FROM AUTHOR]

The potential use of metamaterial planar bilayers for synthesizing compact subwavelength leaky-wave radiators in the microwave regime is analyzed in detail. In particular, the possibility of pairing "complementary" metamaterials in order to reduce the dimensions of microwave components is explored for the leaky-wave operation of an open waveguide consisting of a grounded pair of planar layers. In connection with our similar findings in other setups employing such complementary pairings, here we show how the compact resonance at the interface between "negative" and "positive" materials may also be properly exploited in this context. Choosing materials with low constitutive parameters, moreover, shows to be effective for enhancing the directivity of these components. We explore in detail the notable guidance and radiation properties of the anomalous natural modes supported by these bilayered structures, giving some physical insights into the anomalous phenomenon and considering the possible limitations in some realistic setups. [ABSTRACT FROM AUTHOR]

Recently, there has been an increased interest in the problem of wave transmission through sub-wavelength apertures, following successful experimental demonstration by several groups for enhancing optical power transmission through nano-scale holes in metallic screens due to properly designed periodic corrugation. Oliner, Jackson, and their co-workers explained and justified this phenomenon as the result of the excitation of the leaky waves supported by the corrugated screen. Here we discuss in detail the mechanism and analysis for another setup we have recently proposed, in which metamaterial layers with special parameters may be utilized as covers over a single sub-wavelength aperture in a perfectly electric conducting (PEC) flat screen in order to increase the wave transmission through this aperture, and we provide a detailed physical insights and analytical explanation for this aperture setup that may lead to similar, potentially even more pronounced effects when the proper metamaterial layers are used in the entrance and the exit face of the hole in the flat PEC screen with no corrugation. Some numerical results confirming this theory are presented and discussed. We also investigate the sensitivity of the transmission enhancement to the geometrical and electromagnetic parameters of this structure. [ABSTRACT FROM AUTHOR]

An effective design of polygonal patch antennas with multifrequency or broad-band operation modes for wireless communications is presented in this paper. It is shown how polygonal patches with suitable features may be obtained after a proper perturbation of conventional rectangular geometries, which inherently present poor bandwidth performances. These perturbed irregular geometries may support multiple resonances and, thus, may present a broad-band or multifrequency operation mode, even employing conventional patch antennas with a single dielectric substrate. These polygonal patches are efficiently analyzed through a numerical code based on the method of moments, with entire domain basis functions that accurately describe the radiation mechanism. After the presentation of the analysis and design techniques, some antenna layouts for modern wireless communication systems will be proposed. Such antennas are designed for both universal mobile telecommunication system and wireless local area network portable equipment with real-life finite ground planes. [ABSTRACT FROM AUTHOR]

This paper presents a generalization of the method of lines (MoL) numerical algorithm for the analysis of integrated structures with a finite local curvature. Starting from the derivation of the generalized transmission line equations in a generic orthogonal reference system and in a bianisotropic material, it is shown the possibility of solving the electromagnetic problem associated to an integrated structure with arbitrary curvature and/or loaded by complex dielectric materials via a MoL approach. The introduction of new algorithms that extend and complete the original method is required in the most general case. A detailed description of this new extended version of the MoL is presented through the paper and its full coincidence with the original algorithm in the case of structures with simple loading materials is also shown. Finally, some numerical results obtained analyzing microwave conformal antennas and resonators are presented and compared with analyzes performed employing other numerical methods and available in the literature. [ABSTRACT FROM AUTHOR]

Presents the results of a theoretical analysis for guided modes in parallel-plate waveguides filled with pairs of parallel layers. Salient properties of the guided modes; Ways in which materials and their parameters are chosen to be paired; Contrast with those of the guided modes in conventional waveguides; Physical insights and intuitive justifications for the mathematical findings.

This paper develops a quasi-analytical and self-consistent model to compute the polarizabilities of split ring resonators (SRRs). An experimental setup is also proposed for measuring the magnetic polarizability of these structures. Experimental data are provided and compared with theoretical results computed following the proposed model. By using a local field approach, the model is applied to the obtaining of the dispersion characteristics of discrete negative magnetic permeability and left-handed metamaterials. Two types of SRRs, namely, the so-called edge coupled- and broadside Coupled- SRRs, have been considered. A comparative analysis of these two structures has been carried out in connection with their suitability for the design of metamaterials. Advantages and disadvantages of both structures are discussed. [ABSTRACT FROM AUTHOR]

Method of line (MOL) procedure is very useful in the analysis of radiative and transmissive microwave components, but its standard version does not allow for the study of elements with complex substrates. In this work, we first show that components integrated into materials exhibiting the magneto-electric effect (biisotropic and general bianisotropic media) cannot be analyzed following a standard MoL algorithm. Next, we derive an extended MoL numerical tool, which allows for the analysis of components in the presence of any linear medium (even inhomogeneous, bianisotropic and lossy). Such an extension is based on the generalization of the transmission.line equations for a general linear medium, which, in the case in point, are not necessarily decoupled. Furthermore, we present the full coincidence of this new method with the standard MoL in the case of simpler media (i.e., not exhibiting the magneto-electric effect) and, finally, we show some numerical results, obtained analyzing microwave antennas and resonators with bianisotropic and chiral substrates. [ABSTRACT FROM AUTHOR]