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In the context of the optimization of a versatile type of metasurface consisting of intertwined spirals printed on a dielectric substrate and loaded with discrete impedances, we propose a simple development of the method of moments interaction matrix that allows obtaining the scattered field almost instantly for any distribution of discrete loads. Simulation results for a sample design are presented...
In the presence of a conductive slab, the mutual inductance of two coupled coils is no longer a real number but becomes a complex quantity whose modulus declines for increasing conductivity and thickness of the slab. In this work, we investigate the case when the two coils are entirely embedded in a conductive medium and derive new analytical formulae for the magnetic vector potential of a coil in...
Arrays of coupled split ring resonators (SRRs) capable of carrying slow short-wavelength magneto-inductive waves have been shown to support the rapidly varying current distributions required for superdirectivity. However, the superposition of both electric and magnetic dipole resonance modes contributing to radiation of SRRs challenge pure physical intuition in the selection of the optimal dimer configuration...
A reflect-type metasurface with phase gradient discontinuity is proposed. It is formed by planar intertwined spiral conductors loaded with inductors. A pattern of conductors is initially designed under the assumption of locally periodicity and the phase response of uniform arrays. Simulations are performed with a fast proprietary code based on the periodic Method of Moment and the Array Scanning Method...
We have studied analytically, numerically and experimentally the effect of conducting material upon the mutual inductance between two coils yielding thereby the attenuation of magnetoinductive (MI) waves. It is shown among others that the expression for plane wave attenuation, used in the literature, has only limited validity. Our results will be relevant for the design and optimisation of MI waveguide...
A century-long quest for realizing superdirective antennas has got a new lease of life with the advent of metamaterials: Arrays of coupled meta-atoms capable of carrying slow short-wavelength magneto-inductive waves were shown to be promising candidates for realizing rapidly varying current distributions required for superdirectivity. This paper provides an overview of our work towards realizing a...
A broad class of metasurfaces comprised of periodic arrays of interwoven multifilar spiral shaped strips and slots in conducting screens has been developed. The proposed array topologies with truly sub-wavelength unit cells enable efficient control of the unit cell reactance while maintaining excellent angular and polarization stability of their response over extended fractional bandwidths. The distinctive...
A reconfigurable metasurface (MS) composed of a periodic array of dogbone shaped conductor pairs and embedded varactor diodes is analyzed with the aid of a qualitative analytical model and simulated numerically. It is demonstrated that electric and magnetic type resonances are independently controlled by applying bias to specific subsets of varactor diodes. The predictions of the analytical model...
High impedance metasurfaces (HIMSs) formed by interwoven conductor arrays are proposed. Bandwidth comparable with that of the basic square patches is achieved at an order of magnitude smaller unit cells. The presented structures are apt for small mobile terminals and low frequency applications.
A high impedance metasurface (HIMS) composed of the arrays of intertwined planar spirals on thin (∼0.1λ) ferrite-dielectric substrate is proposed. The HIMS exhibits fractional bandwidth in excess of 10% and excellent angular and polarisation stability of the circular polarised waves at oblique incidence.
The emphasis placed on the novel properties and application potential of metamaterials in recent years has increased research interest in understanding the interaction between these composite structures and electromagnetic radiation. Such an interaction can be conveniently characterized using homogenization methods, which describe metamaterials as bulk homogeneous materials with certain effective...
Metamaterials and plasmonics based on micro- and nanostructured metallic-dielectric composites are bringing an important revolution to the microwave and optics fields due to their potential for enabling the realization of novel physical properties unattainable from natural materials, such as isotropic negative refraction, slow light, near-field enhancement, as well as EM focusing and energy transfer...
The features of artificial surfaces composed of doubly periodic patterns of interwoven planar conductors are discussed. The free-standing intertwined quadrifilar spirals and modified Brigid's crosses are presented as illustrative examples to demonstrate the highly stable angular reflection and transmittance response with low cross-polarisation and a broad fractional bandwidth. The main mechanisms...
The concept of intertwining planar spirals recently proposed for quadrifilar spirals is shown to be applicable to spiral arrays with other lattice symmetries and complementary layouts. In particular, the features of trifilar and hexafilar intertwined spirals arranged in doubly periodic arrays with triangular and hexagonal lattices are discussed.
In this paper we analyze the propagation through a metamaterial in planar technology recently proposed. The metamaterial basic constituent cell consists of a pair of tightly coupled conductors that supports two main resonance modes corresponding to either a symmetric or an antisymmetric current distribution in the pair. We present an equivalent X-shaped lumped circuit network to be interposed in the...
A challenging task in array design is to synthesize an array working at multiple frequencies within a large frequency band, with constraints imposed to the radiation pattern in terms of side lobe level (SLL). This kind of array synthesis requires a multi-objective approach since there is no single solution which can be considered the best at the multiple investigated frequencies for all the compulsory...
The metamaterials composed of planar arrays of tightly coupled dogbone-shaped conductors have recently attracted considerable interest owing to their potential of supporting backward wave propagation [l]-[3]. The detailed study of the plane wave interaction with a layer of dogbone pairs has been performed in [3], [4] along with the eigenwave analysis of an infinite stack of array layers. In particular,...
This work investigates certain electromagnetic (EM) properties of metamaterials formed by densely arrayed nanoclusters of plasmonic nanoparticles. An approximate model based on the single dipole approach in conjunction with the multipole expansion of the scattered field is used to evaluate the electric and magnetic polarizabilities of the nanocluster. Then, the permittivity and permeability of the...
We present a fully planar realization of a low profile dipole antenna placed on top of a high impedance substrate. The structure is made by three metal layers and it does not requires vias between the layers. The antenna is matched to 50 Ohms and has a gain of 7.1 dBi including all feed network losses.
The distinctive features and properties of metamaterials containing the constitutive particles composed of tightly coupled pairs of the dogbone shaped conductors and planar spirals are discussed. The results of the full-wave simulations and measurements of the scattering characteristics of such arrays will be presented to illustrate the main concepts of such artificial media.
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