Both Fano resonance and toroidal response can also be simultaneously excited in a stacked configuration of asymmetric split-ring resonators. Recently, toroidal metamaterials have been successfully used for sensing and switching applications. A different configuration proposed by the same group achieves Fano resonance observed in electromagnetically induced transparency system in addition to the toroidal response. used asymmetric mirrored double split-ring structure and a combination of the split ring with dogbone metalization to generate toroidal dipole resonances in planar media. One such 3D configuration is the split loop structures immersed in a dielectric medium. In conventional artificial media, a careful design procedure must be followed to suppress the excitation of electric and magnetic dipoles and to enhance toroidal dipole response. They can also be used for creating a negative refractive index medium. Artificial media exhibiting strong toroidal excitation are used for the creation of electromagnetically induced resonant transparency. Recently, there has been an immense interest in the development of toroidal metamaterials for electromagnetic wave manipulations. The far-field scattering pattern of a toroidal dipole is indistinguishable from that of an electric dipole. Their excitation in the nuclear system was first reported by Zel’dovich.
Toroidal dipoles are exempted from classical multipole expansion theory and are caused due to the surface current circulating on a metallic torus along its meridians. The simultaneous excitation of electric and magnetic dipoles is used to tailor both magnitude and phase of transmission/reflection coefficients from a metamaterial composite. An electric dipole is created by the separation of positive and negative charges, whereas a magnetic dipole is generated by virtue of circulating currents on a composite. The classical electromagnetic theory accounts only the scattering from electric and magnetic dipoles in the multipole scattering formalism. The simulation and experimental results investigated the idea of the beam focusing using electromagnetic coupling improvement based on three dimensional periodic structures of circular split ring resonators and thin wires in microwave regime.Recent research interest has been focused on the scattering studies of a special type of excitation known as toroidal dipoles in composite metamaterial structures.
#Wire antenna excitation cst microwave studio Patch#
Furthermore, the results show that, the antenna gain is improved by 4.6 dB while the beam width is reduced from 75° to 41° which validate the concept of beam focusing using electromagnetic coupling between the patch and the three dimensional periodic structure and between the different unit cells of the periodic structure, and also the return loss is improved by -20 dB, while the bandwidth is slightly reduced. For experimental verification, the proposed antenna operating at 10 GHz is fabricated the return loss and the gain for the proposed antenna with and without metamaterial are measured. The impacts of the separation distance between the patch and three dimensional periodic structures and the size of the three dimensional periodic structure on the radiation and impedance matching parameters of the proposed antenna are studied. A parametric analysis has been performed on the proposed antenna incorporated with the three dimensional periodic structure. The infinite periodicity of the two dimensional periodic structure is then truncated and multi layers of such truncated structure is used to construct a three dimensional periodic structure. An infinite two dimensional periodicity unit cell of circular split ring resonator and thin wire is designed to resonate at a 10 GHz and simulated in CST software, the scattering parameters are extracted, the results showed that the infinite periodicity two dimensional structure has a pass band frequency response of good transmission and reflection characteristics around 10 GHz. The proposed antenna has been designed and simulated using CST microwave studio at 10 GHz.
As a result, the electric and the magnetic fields at the top of the patch are improved, the radiated electromagnetic beam size reduces which results in a highly focused beam and hence the antenna directivity and gain are improved, while the beam are is reduced. These enhancements occur between the patch and the periodic structure resonators and between the different resonator pairs of the periodic structure.
The radiated electromagnetic waves intensity of the proposed antenna is improved compared with the conventional patch antenna due to the electric and magnetic coupling enhancements. The three dimensional periodic structure is placed at the top of the patch within a specific separation distance to construct the proposed antenna. In this paper, three dimensional periodic structure composed of circular split ring resonators and thin wires is used to improve the performance of a microstrip patch antenna.
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