Pair Of Split Ring Resonators Research Articles

A Dual Reconfigurable Printed Antenna: Design Concept and Experimental Realization

In this article, we demonstrate the design concept and experimental realization of a dual reconfigurable printed antenna. A single coplanar waveguide (CPW)-fed printed monopole antenna can provide a reconfigurable ultrawideband (UWB)-notched or narrow-band (NB) response, depending on the status of the switches and the position of the split ring resonators (SRRs) in the CPW feed region of the antenna. The rectilinear movement of the superstrate, printed with various pairs of SRRs of differing dimensions, loaded in the feed region of the antenna, provides the reconfigurable functionalities. The position of the superstrate is controlled by a commercial servo motor programmed by a microcontroller. The antenna, along with the additional accessories required to actuate the mechanical movement, are fabricated and characterized using impedance and radiation pattern measurements. The measured results for both reconfigurable cases provide a good correspondence with the simulated results and the theoretical estimation. The proposed antenna can be used as a reconfigurable communicating antenna module of the cognitive radio (CR) system.

Application of Split Ring Resonator (SRR) Loaded Transmission Lines to the Design of Angular Displacement and Velocity Sensors for Space Applications

The accurate measurement of the angular displacement and velocity of reaction wheels is necessary for attitude (orientation) control in space vehicles (satellites). In this paper, microwave, contactless, and low-cost (as compared to optical encoders) sensors useful for that purpose are analyzed in detail. The sensor consists of a rotor and a stator. The rotor is a disk (or a circular crown) of dielectric material, where one or several arrays of equidistant single-loop split ring resonators (SRRs) are etched along its edge, forming circular chains of hundreds of SRRs. The stator is a coplanar waveguide (CPW) also loaded with pairs of single-loop SRRs (etched in the back substrate side), with the centers located in the slot region. The sensing principle is based on the amplitude modulation of a harmonic (single-tone continuous wave) feeding signal, achieved when the chains of the rotor are displaced over the SRR pairs of the stator. Both sensor elements (rotor and stator) must be parallel oriented, with the SRR pairs of the CPW in close proximity to the SRR chains of the rotor (and rotated 180°), in order to favor their coupling. By this means, the transmission coefficient of the CPW is varied by the circular motion of the rotor, and significant amplitude modulation of the feeding signal is achieved. From the envelope function, the angular velocity can be accurately determined. With the proposed sensors, instantaneous and practically unlimited rotation speeds can be measured.

Resonance coupling and polarization conversion in terahertz metasurfaces with twisted split-ring resonator pairs.

We investigate edge-coupling of twisted split-ring resonator (SRR) pairs in the terahertz (THz) frequency range. Using a simple coupled-resonator model we show that such a system exhibits resonance splitting and cross-polarization conversion. Numerical simulations and experimental measurements agree well with theoretical calculations, verifying the resonance splitting as a function of the coupling strength given by the SRR separation. We further show that a metal ground plane can be integrated to significantly enhance the resonance coupling, which enables the effective control of resonance splitting and the efficiency and bandwidth of the cross-polarization conversion. Our findings improve the fundamental understanding of metamaterials with a view of accomplishing metamaterial functionalities with enhanced performance, which is of great interest in realizing THz functional devices required in a variety of applications.

Probing the Near-Field Inductive Coupling in Broadside Coupled Terahertz Metamaterials

We discuss near-field coupling between the pair of split ring resonators (SRRs) in broadside coupled terahertz (THz) metamaterials and examine resonance split and tuning of resonances in such metamaterials system. The metamolecule design is comprised of two orthogonally twisted broadside coupled SRRs separated by a thin microscale polyimide layer. We analyze the interaction between the metalayers numerically and analytically by displacing the top resonator w.r.t. the bottom resonator both in the horizontal and vertical directions. The THz transmission through proposed configuration results in the split of fundamental resonances due to the resonance mode hybridization effect. In the case of successive horizontal displacements between the resonators, we observe a complete shift from the coupled to uncoupled state, however, in vertical displacements, we notice the transition from coupled to uncoupled state at much larger displacement. We employed a semianalytical transmission line model to understand and describe the coupling aspect between the bilayer resonators and found that it corroborates the numerical findings. The ability to tune resonance behavior that we have examined through this work, could be significant in the development of frequency tunable THz devices and build other promising applications such as THz modulators and antennas in the near future.

SRR and S-shape slot loaded triple band notched UWB antenna

This paper demonstrates the design of a triple band notched ultrawideband circular microstrip patch antenna loaded with Complementary Split RingResonator (CSRR) and S-shaped slot in microstrip feed line. Complementary Split Ring Resonator slot and S-shaped slot are used to produce band notched characteristics for WiMAX band (3.30–3.60GHz) and WLAN band (5.10–5.80GHz) respectively. The downlink frequency band (7.25–7.75GHz) of X-band for satellite communication is notched using Symmetrical Split Ring Resonator Pair (SSRRP) as electromagnetic coupling element near microstrip feed line which produces band stop characteristics. Measured results of fabricated antenna prototype are compared with simulated results and found in correspondence. The VSWR and vector current plots show evidence of the significant suppression in the desired frequency bands.

Multiband omnidirectional planar monopole antenna with two split ring resonator pairs

This letter presents a printed planar monopole antenna with triple-band operation. By adding two symmetrical split ring resonator (SRR) pairs to the primitive monopole antenna, the wireless local area network (WLAN), and worldwide interoperability for microwave access (WiMAX) bands operating at 2.45/3.5/5.8 GHz can be obtained. The inserted SRR pairs exhibit both the radiation and the nonradiation mode of operations, from which the proposed antenna works in triple band. The principle of how these two modes give us the multiband operation is explained. The antenna was fabricated and measured to confirm the characteristics of the proposed design. The simulated and experimental results are in close agreement. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:753–758, 2017

Enhanced-gain printed slot antenna using an electric metasurface superstrate

In this article, a method to enhance the radiation characteristics of a slot antenna by using an electric metasurface as a high refractive index superstrate has been presented. The gain enhancement mechanism described here uses the phenomena of enhanced space field by increasing the effective aperture of the antenna, resulting from increase in effective refractive index of the metasurface. As a fundamental constituent of the superstrate, a unit cell of the metasurface composed of symmetrically placed triple pairs of split-ring resonators is introduced. The unit cell of such metasurface has been configured to realize a high refractive index by using the principle of nearest-neighbor coupling. An equivalent circuit model is developed to understand the influence of coupling on the effective refractive index of the metasurface. The presence of the metasurface as a superstrate enhances the broadside gain of the slot by 8.71 dB and the efficiency by 20.35 %. The total height of the proposed configuration is 0.237 λ 0 where λ 0 is the free space wavelength at the resonance frequency of the slot antenna.

Ultra‐wideband monopole antenna for multiband and wideband frequency notch and narrowband applications

A new design concept of a multi-configuration antenna providing both frequency notched ultra-wideband and multiple narrowband functionality from a coplanar waveguide fed circular monopole antenna is presented in this study. The proposed multiple antenna configurations are achieved by loading the feed section of the antenna with circular split ring resonator pair of varying dimensions and inner ring orientations and shorting copper strips. Fabricated prototypes were measured and compared with simulation and good agreement is obtained for both impedance and radiation characteristics.

Metamaterial loaded vivaldi antenna with high gain and equal beamwidths at KA band

ABSTRACTA high gain and broadband Vivaldi antenna with end‐fire and equal beamwidth radiation pattern at Ka band is presented in this paper. The Vivaldi slot is fed by the microstrip line‐to‐substrate integrated waveguide (SIW) transformer. The SIW transmission performance is enhanced by another row of metal vias beside the original one. On both sides of the Vivaldi conductor planes, 8 parallel slots with gradually increasing length are etched to improve the front‐to‐back ratios. Under the microstrip feed line, three pairs of split ring resonators (SRRs) are etched on the ground to suppress the secondary harmonic. In order to improve the antenna gain and obtain the equal E‐ and H‐plane beamwidths, the special designed zero‐epsilon metamaterial (ZEM) units are loaded on the Vivaldi slot with a maximum gain increment of 3.4dB being obtained. The antenna exhibits a broad bandwidth of 38.5% at 35GHz ranging from 26.5GHz to 40GHz with the reflection coefficient less than −10dB, and the gain varying between 9.7dBi and 12.2dBi. The proposed antenna is fabricated and measured to validate the design. The measured results are in good agreement with the simulated ones. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2337–2341, 2016

Thermally tunable electromagnetically induced transparency in terahertz frequency with superconducting resonators

We present a design of electromagnetically induced transparency operating in terahertz regime based on near-field coupling between a metal strip and split ring resonators (SRR) made of superconducting film. When the SRR work in superconducting state, the transparency window can be thermally controlled. A pair of SRR has been introduced as the dark mode to enhance the coupling, which results in a broadening and high transmittance of near unity of the transparency window. These results may lead to potential applications in tunable terahertz devices, slowing light, and sensing technology.

Polarizability Tensor Retrieval for Subwavelength Particles of Arbitrary Shape

We present a semianalytical method to determine the full polarizability tensor of subwavelength particles with arbitrary shape and composition. This method extracts both co- and cross-coupling terms of the polarizability tensor, retrieving the full 6 × polarizability tensor with three measurements, by appropriately rotating the inclusions, when embedded in a planar periodic array, with respect to their principle axes. In order to validate this method, we present four examples, including a magnetodielectric sphere, a magnetodielectric spheroid, a conducting helix and pairs of split-ring resonators, and discuss the relation with fundamental constraints such as reciprocity and Onsager's relations. We also discuss how this retrieval method may be useful for the design and homogenization of periodic metamaterials and two-dimensional (2-D) metasurfaces formed by subwavelength inclusions.

Design and simulation of a compact ultra-wideband bandpass filter with a notched band using multiple-mode resonator technique

A novel, compact, and highly selective ultra-wideband (UWB) bandpass filter with a narrow notched band is presented. Apart from having a basic structure of a slotline multiple-mode resonator (MMR) and microstrip feed lines, this novel design introduces a cross-coupling between the input and output feed lines to enhance the filter selectivity. The design strictly follows the theory and verified by electromagnetic (EM) simulation and experiments. In addition, the narrow notched band is introduced by embedding a pair of split ring resonators (SRR) in order to reject any undesired existing radio signals that may interfere with the Federal Communications Commission (FCC)-defined UWB band. By changing the structural parameters of SRR, it can be easily tuned to any desired frequency. This filter can be integrated in UWB communication systems and efficiently improve the interference immunity from undesired signals such as wireless local area network (WLAN).

Resonance control of mid-infrared metamaterials using arrays of split-ring resonator pairs

We present our design, fabrication and characterization of resonance-controllable metamaterials operating at mid-infrared wavelengths. The metamaterials are composed of pairs of back-to-back or face-to-face U-shape split-ring resonators (SRRs). Transmission spectra of the metamaterials are measured using Fourier-transform infrared spectroscopy. The results show that the transmission resonance is dependent on the distance between the two SRRs in each SRR pair. The dips in the transmission spectrum shift to shorter wavelengths with increasing distance between the two SRRs for both the back-to-back and face-to-face SRR pairs. The position of the resonance dips in the spectrum can hence be controlled by the relative position of the SRRs. This mechanism of resonance control offers a promising way of developing metamaterials with tunability for optical filters and bio/chemical sensing devices in integrated nano-optics.

A Novel Ultrawideband (UWB) Printed Antenna With a Dual Complementary Characteristic

A novel design concept for a versatile multi-functional coplanar waveguide (CPW)-fed ultrawideband (UWB) printed antenna is described in this letter. The antenna also exhibits a dual complementary characteristic of frequency notched response and narrowband response invoked by different combinative loading of a pair of split ring resonators (SRRs) and metallic shunt strips on the CPW feed line. The antenna restores its UWB response when the SRRs’ split gaps are shorted. The simulated impedance and radiation characteristics are validated with measured results obtained using fabricated prototypes to establish the proof of concept.

Plasmon-Induced Transparency in Metamaterial Based on Graphene and Split-Ring Resonators

We present a design of a terahertz plasmon induced transparency (PIT) metamaterial based on a graphene patch and split-ring resonator (SRR) pair. The PIT metamaterial exhibits a sharp-induced transparency peak resulting from the destructive interference between the direct-excited plasmon resonance in the graphene patch acting as the bright mode and the coupling-excited inductive–capacitive resonance in the SRR pair acting as the dark mode. Tuning the Fermi energy in graphene results in the modulation of the PIT window, allowing for the active control of the group index. These results may lead to promising applications in tunable terahertz devices, slow light, and sensing technology.

A Negative Index Metamaterial-Inspired UWB Antenna with an Integration of Complementary SRR and CLS Unit Cells for Microwave Imaging Sensor Applications.

This paper presents a negative index metamaterial incorporated UWB antenna with an integration of complementary SRR (split-ring resonator) and CLS (capacitive loaded strip) unit cells for microwave imaging sensor applications. This metamaterial UWB antenna sensor consists of four unit cells along one axis, where each unit cell incorporates a complementary SRR and CLS pair. This integration enables a design layout that allows both a negative value of permittivity and a negative value of permeability simultaneous, resulting in a durable negative index to enhance the antenna sensor performance for microwave imaging sensor applications. The proposed MTM antenna sensor was designed and fabricated on an FR4 substrate having a thickness of 1.6 mm and a dielectric constant of 4.6. The electrical dimensions of this antenna sensor are 0.20 λ × 0.29 λ at a lower frequency of 3.1 GHz. This antenna sensor achieves a 131.5% bandwidth (VSWR < 2) covering the frequency bands from 3.1 GHz to more than 15 GHz with a maximum gain of 6.57 dBi. High fidelity factor and gain, smooth surface-current distribution and nearly omni-directional radiation patterns with low cross-polarization confirm that the proposed negative index UWB antenna is a promising entrant in the field of microwave imaging sensors.

An asymmetric split ring resonator for refractive‐based‐sensor applications at terahertz frequencies

ABSTRACTWe have proposed a terahertz metamaterials resonator that consists of a pair of split ring resonators (SRRs) and can be utilized as a refractive‐based‐sensor. Supporting simulations indicate the resonant Q value is up to 90 and a refractive sensitivity of 61.7 GHz/RIU, figure of merit value of 10.74, correspondingly. Resonator sample of the “connected SRR” has been fabricated and measured using a terahertz time‐domain spectroscopy system, the transmission characteristics of which are consistent basically with the finite difference time domain simulations. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1132–1135, 2015

Rotational circular split ring resonator array loaded CPW for dual notch and wide bandstop applications

ABSTRACTA compact design of a wide bandstop and dual notch filter using an array of circular split ring resonators (SRR) on a coplanar waveguide is proposed in this article. The band rejection is determined by the resonance frequencies of the loaded SRRs. The resonance frequencies of the SRRs are optimized by gradual angular rotation of the inner rings of the SRRs. The dual notch is achieved with dual SRR pairs with two different angular orientations of (0°–60° and 0°–90°). A wideband rejection is achieved by an array of eight pairs of SRRs with gradually changing angular orientation from 0° to 90°. Good agreement is achieved between the simulated and the measured results. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1204–1209, 2015

Analysis of transmission lines loaded with pairs of coupled resonant elements and application to sensors

This paper is focused on the analysis of transmission lines loaded with pairs of magnetically coupled resonators. We have considered two different structures: (i) a microstrip line loaded with pairs of stepped impedance resonators (SIRs), and (ii) a coplanar waveguide (CPW) transmission line loaded with pairs of split ring resonators (SRRs). In both cases, the line exhibits a single resonance frequency (transmission zero) if the resonators are identical (symmetric structure with regard to the line axis), and this resonance is different to the one of the line loaded with a single resonator due to inter-resonator coupling. If the structures are asymmetric, inter-resonator coupling enhances the distance between the two split resonance frequencies that arise. In spite that the considered lines and loading resonators are very different and are described by different lumped element equivalent circuit models, the phenomenology associated to the effects of coupling is exactly the same, and the resonance frequencies are given by identical expressions. The reported lumped element circuit models of both structures are validated by comparing the circuit simulations with extracted parameters with both electromagnetic simulations and experimental data. These structures can be useful for the implementation of microwave sensors based on symmetry properties.

Ultrafast optical control of group delay of narrow-band terahertz waves

We experimentally demonstrate control over the group delay of narrow-band (quasi continuous wave) terahertz (THz) pulses with constant amplitude based on optical switching of a metasurface characteristic. The near-field coupling between resonant modes of a complementary split ring resonator pair and a rectangular slit show an electromagnetically induced transparency-like (EIT-like) spectral shape in the reflection spectrum of a metasurface. This coupling induces group delay of a narrow-band THz pulse around the resonant frequency of the EIT-like spectrum. By irradiating the metasurface with an optical excitation pulse, the metasurface becomes mirror-like and thus the incident narrow-band THz pulse is reflected without a delay. Remarkably, if we select the appropriate excitation power, only the group delay of the narrow-band THz pulse can be switched while the amplitude is maintained before and after optical excitation.