Broadside-coupled Split Ring Resonators Research Articles

Magnetic control of negative permeability metamaterials based on liquid crystals

We report on the tunability, by a magnetic field, of a negative permeability metamaterial consisting of stacked arrays of broadside-coupled split ring resonators infiltrated with liquid crystals (LCs). The resonant frequency shift was numerically assessed by a rigorous anisotropic analysis of the reorientation of LC molecules. Experiments were carried out with a prototype designed and fabricated for X-band operation and infiltrated with a nematic compound with optical birefringence Δn=0.18. Scattering parameters vectorial analysis shows a good agreement between the resonant frequency shifts predicted under anisotropic conditions and those measured under static magnetic control.

Characterization and Modeling of Left-Handed Microstrip Lines With Application to Loop Antennas

This study investigates in detail the left-handed (LH) properties of the two-layer microstrip line, periodically loaded with broadside-coupled split ring resonators (BC-SRRs) and vias. The mechanism of the left-handed microstrip line (LHML), which includes the diamagnetic response, the backward-wave propagation and the proportionality of the guided wavelength on frequency, is discussed in terms of the field and current distributions and the dispersion diagram. To examine the resonance of the BC-SRR, both the full-wave eigenmode analysis and the closed-form formula based on the quasistatic approach are developed. The effects of the BC-SRR shape on the resonant frequency are evaluated. To facilitate the computer-aided-design (CAD) applications of the LHML, the equivalent-circuit model, which comprises the three-conductor coupled microstrip line for the coupling section, the series LC for the BC-SRR, and the shunt inductance for the via, is established. Good agreement among the results of the full-wave simulation, equivalent-circuit model, published data, and measurement supports the usefulness of the proposed modeling methodology and also validates the analytical expressions. The application of the LHML in the microstrip rectangular loop antenna fed by the conductor-backed coplanar waveguide-to-conductor-backed coplanar stripline (CBCPW-to-CBCPS) transition is presented to highlight the unique features of the LHML. Compared with the conventional loop antenna, the LHML-loaded loop antenna achieves a 50% area reduction and the 52% of main beam steering.

Reducing losses and dispersion effects in multilayer metamaterial tunnelling devices

This paper focuses on reduction of losses and dispersion effects on tunnelling through waveguides filled with metamaterial. It will be shown that these unwanted effects could be reduced by dividing the metamaterial into several regions separated by air slabs. In the first part, these effects will be studied for isotropic left-handed media (LHM). Later this will be substituted by an anisotropic magnetic medium which will lead to a practical realization with broadside coupled split ring resonators (BC-SRRs). Finally, it is shown that quasi-perfect tunnelling is possible, even in the presence of unavoidable losses and dispersion in the metamaterial.

On the resonances and polarizabilities of split ring resonators

In this paper, the behavior at resonance of split ring resonators (SRRs) and other related topologies, such as the nonbianisotropic SRR and the broadside-coupled SRR, are studied. It is shown that these structures exhibit a fundamental resonant mode (the quasistatic resonance) and other higher-order modes which are related to dynamic processes. The excitation of these modes by means of a properly polarized time varying magnetic and/or electric fields is discussed on the basis of resonator symmetries. To verify the electromagnetic properties of these resonators, simulations based on resonance excitation by nonuniform and uniform external fields have been performed. Inspection of the currents at resonances, inferred from particle symmetries and full-wave electromagnetic simulations, allows us to predict the first-order dipolar moments induced at the different resonators and to develop a classification of the resonances based on this concept. The experimental data, obtained in SRR-loaded waveguides, are in agreement with the theory and point out the rich phenomenology associated with these planar resonant structures.

Comparative analysis of edge- and broadside-coupled split ring resonators for metamaterial design - Theory and experiments

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.