Double Split Ring Resonator Research Articles

Microwave sensing of ammonia and iron concentration in water based on complementary double split-ring resonator

This work reports an alternative technique based on a complementary double split-ring resonator to determine the concentrations of ammonia and iron in water. The conventional methods for measuring ammonia and iron concentration involve expensive and bulky instruments in the laboratory. Furthermore, the current methods involve hazardous chemical reagents and complicated procedures. In this work, a low-cost microwave sensor which is portable and easy to operate is proposed. The water samples that have different ammonia or iron concentration is dropped deposited at the sensing area. Their concentration is determined based on the shifting of the resonance frequency in the measurement. The measurement results indicate that the resonance frequency of the resonator reduced from 2.38 GHz (unloaded condition) to a low-frequency range when the water sample containing different concentrations of ammonia or iron are introduced to the sensing area. Based on the collected results, Fourier models are used to establish the relationship between the concentrations of ammonia and iron (in the range of 0 to 53 mg/L) to the resonance frequency shifting. The validity of these models is proven as they introduced a root mean square error (RMSE) of less than 0.009. The findings of this work demonstrated the feasibility of the microwave sensor in detecting water pollutants.

A Transmissive Linear Polarization and Circular Polarization Cross Polarization Converter Based on All-Dielectric Metasurface

In this article, we propose a metasurface with C2 symmetry in the terahertz band, which consists of an external ring resonator and an inner double split ring resonator. In order to overcome the problems of ohmic loss and low transmission efficiency caused by the metal structure, we selected all-dielectric materials to design. From 2.17 THz to 2.24 THz, through numerical simulation, the device we proposed can achieve high-efficiency cross-polarization conversion of linearly polarized waves and circularly polarized waves, and their transmission efficiency exceeds 0.8. We first explained it through polarization orthogonal decomposition, and then the physical mechanism is investigated specifically by the distribution of electric field and magnetic field, and the influence of structural parameters on the device is also discussed. In addition, the cell we proposed has a thickness of about λ/10, which is conducive to the design and integration of terahertz devices and systems.

Graphene-Based Plasmonic Absorber for Biosensing Applications Using Gold Split Ring Resonator Metasurfaces

We propose a novel graphene-based metasurface plasmonic biosensor. The gold split-ring resonator is used as a metasurface element in the biosensor. Split Ring Resonator structures are used to localize and increase electromagnetic field incidents. Two types of split-ring resonator based metasurface (Single split-ring resonator and Double split-ring resonator) designs are analyzed to observe its effect on biosensing. The proposed biosensor is used to sense hemoglobin and urine biomolecules for their different concentrations. The design results in the form of absorption, electric field, and magnetic field are presented. The sensitivity for hemoglobin biomolecules and urine biomolecules are calculated from their absorption peak difference and refractive index difference. The sensitivity results are compared with previously published designs. The proposed single split ring resonator metasurface design has the highest sensitivity for hemoglobin-urine concentrations. The proposed biosensor can become a building block for future medical biosensing devices.

Design and Analysis of Metamaterial based-check board AMC Backed EBG Antenna for Body Placement Applications

In this paper a compact EBG antenna with Artificial Magnetic Conductor (AMC) is proposed for on body applications. The proposed antenna is designed with single SRR (split ring resonator) and double SRR to differentiate the performance of the proposed antenna. The proposed EBG antenna bending analysis is performed at different angles on human body to attain good radiation characteristics. The footprint of proposed antenna is of 0.2λ0*0.24λ0mm2 and AMC with dimension of 0.48λ0*0.48λ0 mm2.The proposed antenna is obtained good return loss and radiation characteristics when EBG antenna is placed on the human leg with an angle of 300 at corresponding operating frequencies 2.4GHz, 5.8GHz, 9GHz and 9.5GHz respectively. The obtained operating frequencies cover wireless applications such as GPS, ISM, and Radar and satellite communications. The proposed EBG antenna is obtained with high gain 7.05dBi at 9.5GHz operating frequency. The surface current distributions are obtained for the proposed antenna is of 137A/m. Good isometric radiation patterns are observed for the proposed antenna. The SAR analysis is performed when the EBG antenna is placed on the human leg at an angle of 30degree is of 1.23W/kg.

Terahertz hybrid metal-graphene metamaterials with tunable dual-band electromagnetically induced transparency

The electromagnetically induced transparency (EIT) effects in metamaterials have been widely studied due to their broad application prospects in the field of optical communications. Previous researchers focused mainly on the regulation of a single EIT effect. Here we proposed a structure containing two pairs of asymmetric C-shaped double-split ring resonators (DSRRs) placed on the two sides of cut wire (CW), and we studied the EIT effect of the structure. Furthermore, in order to tune the EIT peak, two graphene strips are placed on the two pairs of DSRRs. Simulation results show that, the EIT peak can be modulated by adjusting the Fermi level of the graphene strips and the modulation depths as high as 83 % and 87 % can be realized. Besides, slow light phenomenon accompanied by the EIT effect in the structure was investigated. Simulation results implied that, double group delays of 4.4 ps and 3.4 ps can be achieved in the design, and the delays can be adjusted by changing the graphene Fermi level. The physical mechanism of the tunable metamaterial was analyzed in terms of the three-oscillator model.

Active manipulation of dual transparency windows in dark–bright–dark mode coupling graphene metamaterial

Active manipulation of dual transparency windows for EIT metamaterial in dark–bright–dark coupling mode, which is constructed by three graphene patterns, including graphene strip and two asymmetrical double-split graphene ring resonators, is numerically and theoretically investigated in terahertz regime. Simulation results illustrate that the causation of dual-windows EIT phenomenon is the near field coupling of two adjacent graphene patterns in the unit cell which acted as dark and bright mode respectively. In addition, dual transparency windows of EIT can be actively and selectively tuned to realize red or blue shift via varying of the Fermi energy of the corresponding dark mode element in the unit cell. Meanwhile, when the Fermi energies of dark mode elements are shifting inversely, dual transparency windows could be actively modified to single transparency window or even disappeared.

Lightweight porous silica foams with extreme-low dielectric permittivity and loss for future 6G wireless communication technologies

In the next generation wireless communication systems operating at near terahertz frequencies, dielectric substrates with the lowest possible permittivity and loss factor are becoming essential. In this work, highly porous (98.9% ± 0.1%) and lightweight silica foams (0.025 ± 0.005 g/cm3), that have extremely low relative permittivity (εr = 1.018 ± 0.003 at 300 GHz) and corresponding loss factor (tan δ< 3 × 10−4 at 300 GHz) are synthetized by a template-assisted sol-gel method. After dip-coating the slabs of foams with a thin film of cellulose nanofibers, sufficiently smooth surfaces are obtained, on which it is convenient to deposit electrically conductive planar thin films of metals important for applications in electronics and telecommunication devices. Here, micropatterns of Ag thin films are sputtered on the substrates through a shadow mask to demonstrate double split-ring resonator metamaterial structures as radio frequency filters operating in the sub-THz band.

Dual‐band circularly polarized crossed‐dipole antenna with double split‐ring resonators and a defected ground structure

A dual-band cavity-backed circularly polarized crossed-dipole antenna with double split-ring resonators (SRRs) is investigated in this paper. A pair of crossed dipoles connected by concentric ring-delay lines is firstly designed as a circularly polarized (CP) antenna with only one CP mode. To extend the operation of the original design, a pair of the λ/4-resonance SRRs are used to realize wider axial ratio bandwidth at higher band. At the same time, another pair of the λ/4-resonance SRRs with larger dimension is adopted to obtain a lower frequency band, although the effect is not very satisfying. Then the cavity-backed technology and a defected ground structure are both employed to improve the working bandwidth. The dual-band CP antenna can be tuned into a wide bandwidth one by changing the dimensions of the larger SRRs. A good agreement between the simulated and measured results can be observed. The measured impedance bandwidths are 6.90% (3.36-3.60 GHz) and 53.58% (4.40-7.62 GHz). The measured 3-dB AR bandwidth is 7.93% (3.39-3.67 GHz) and 59.15% (4.08-7.51 GHz).

Microwave Polarizer Based on Complementary Split Ring Resonators Frequency-Selective Surface for Conformal Application

In this paper, a microwave polarizer based on frequency selective surface (FSS) loaded with complementary split ring resonator (CSRR) for non-planar and conformal application is presented. The frequency-selective polarizer is fabricated on liquid crystal polymer substrates (LCPs) material with $50\mu \text{m}$ thickness, which shows very good mechanical flexibility for microwave band. The Frequency-selective polarizer consists of a metal FSS screen pair with double complementary split ring resonators aligned in the vertical direction without any displacement. The substrate integrated waveguide (SIW) cavity was introduced to enhance the Q-factor of the CSRR particles and the mechanical strength of the FSS screens at bending conditions. The measured results show that the CSSR-FSS polarizer with the minimum transmission loss for TE-polarization incidence wave is 0.75dB at the 10.24 GHz and 19.05 dB for TM-polarization incidence wave, with an extinction ratio of 18.3dB. Finally, the oblique incidence from normal to 60 degrees and bending tests with the bending radius of 9.8 cm and 8.8 cm of the CSRR-FSSs were also carried out, and the measured results indicate that the CSRR-FSS show a low susceptibility to bending behavior at the small bending radius beyond the 8.8 cm and different incidence angles from normal to 45 degrees. Both the simulated and experiment data indicated that the proposed ultra-thin CSRR-FSS shows excellent flexibility and polarization selectivity.

Realization of Negative Permeability in Vertical Double Split-Ring Resonators with Normal Incidence

With the rapid development of optoelectronics, methods for manipulating light–matter interactions are urgently required. In this work, three-dimensional double split-ring resonators (3D-DSRRs) have...

Double H-shaped complementary split ring resonator with different orientations for quad-band satellite applications

In this study, the structure of the metamaterial was developed on FR-4 substrate with a double H-shaped complementary split ring resonator (CSRR)-based structure for quad-band applications within the satellite band region. To retrieve the scattering parameters, the high-frequency structural simulator for quad-band application, CST Microwave Studio was utilized. Four resonant frequencies within the operating frequency range from 1 to 18 GHz were generated. The bandwidths of these resonant frequencies were between 2.59 and 3.26, 9.39–10.12, 10.6–12.2 and 12.3–12.8 GHz. Different resonant frequencies within the same operating frequency range could be achieved using the structural optimization mechanism. The electric field, magnetic field, and surface current distribution were observed to affect the exotic electromagnetic properties of the proposed metamaterial structure for satellite band applications.

Near-field Terahertz Sensing of HeLa Cells and Pseudomonas Based on Monolithic Integrated Metamaterials with a Spintronic Terahertz Emitter.

Label-free biosensors operating within the terahertz (THz) spectra have helped to unlock a myriad of potential THz applications, ranging from biomaterial detection to point-of-care diagnostics. However, the THz wave diffraction limit and the lack of emitter-integrated THz biosensors hinder the proliferation of high-resolution near-field label-free THz biosensing. Here, a monolithic THz emission biosensor (TEB) is achieved for the first time by integrating asymmetric double-split ring resonator metamaterials with a ferromagnetic heterojunction spintronic THz emitter. This device exhibits an electromagnetically induced transparency window with a resonance frequency of 1.02 THz and a spintronic THz radiation source with a bandwidth of 900 GHz, which are integrated on a fused silica substrate monolithically for the first time. It was observed that the resonance frequency experienced a red-shift behavior with increasing concentration of HeLa cells and Pseudomonas because of the strong interaction between the spintronic THz radiation and the biological samples on the metamaterials. The spatial frequency red-shift resolution is ∼0.01 THz with a Pseudomonas concentration increase from ∼0.5 × 104 to ∼1 × 104/mL. The monolithic THz biosensor is also sensitive to the sample concentration distribution with a 15.68 sensitivity under a spatial resolution of 500 μm, which is determined by the infrared pump light diffraction limit. This TEB shows great potential for high-resolution near-field biosensing applications of trace biological samples.

Exploiting Sensitivity Enhancement in Micro-wave Planar Sensors Using Intermodulation Products With Phase Noise Analysis

In this paper, a new technique to enhance the sensitivity of microwave resonators is introduced. Double split ring resonators are implemented as the core of a loss-compensated resonator. It is illustrated that regenerative oscillators when mixed together can produce higher order intermodulation products (IMP) at the output. The variations in sensing tone are multiplied and exhibit considerably higher sensitivities at 3rd, 5th, and 7th IMP components compared to the main resonant frequency. The sensor is also integrated into wireless platform with ultra-wideband bowtie antennas. Common fluids such as Toluene, n-Heptane, IPA, Ethanol, Methanol, Acetone, and Water are tested in fluidic channel and demonstrated that the sensitivity for intermodulation products are significantly increased proportional to the order of IMP. The proposed sensor is also examined with glucose concentration sensing for the range of 0– 600 mg/dL and significant variation for 7th IMP sensor is observed as opposed to saturation of conventional sensor. Also, asphaltene concentrations down to 6 ppm are recognizable when precipitated from toluene solution using the proposed sensor. Moreover, a rigorous analytical study is presented for phase noise of the IMP originated from reference signals.

Broadband Microwave Absorber with a Double-Split Ring Structure

In this paper, we present a novel broadband microwave absorber. Each unit in the metamaterial consists of a layer of dielectric material sandwiched between two layers of metal patches. Due to metal-dielectric-metal structures consist of symmetric resonators that have low co-polarization and cross-polarization as absorbers, the upper metal layer comprises a novel double-split ring resonator and a central octagonal ring pattern. Our simulation results show that the absorption of the proposed absorber is above 90% in the frequency range from 5.7 to 13.1 GHz. The absorption bandwidth over which the absorptivity exceeds 90% is approximately 7.4 GHz. The calculated relative bandwidth of 78.1% meets the standard for ultra-broadband absorption, and thus has prospects in applications. There are four main resonance frequencies at 6.07, 9.18, 12.75, and 13.11 GHz. And, the absorptivity is not significantly affected by the variation of the incident angle. We find that the resonance phenomenon becomes increasingly prominent as the incident wave frequency increases.

Enhanced toroidal localized spoof surface plasmons in homolateral double-split ring resonators.

In this paper, toroidal localized spoof surface plasmons (LSSPs) based on homolateral double-split ring resonators is proposed and experimentally demonstrated at microwave frequencies. By introducing a new split in the conventional single-split ring resonator, the magnetic field in resonator is locally modified. The double-split ring resonator can create the mixed coupling in the structure, leading to the enhancement of magnetic field. Both numerical simulations and experiments are in good agreement. Compared with traditional toroidal LSSPs based on the single-split ring resonators, the imperfection of toroidal LSSPs is resolved, the intensity of toroidal resonance and the figure of merit (FoM) are significantly enhanced. To understand and clarify the enhanced magnetic field phenomena, we analyze the role of the double-split ring resonator. The effect of location of source and spacing between two splits on the resonance intensity are also discussed. A higher intensity of toroidal LSSPs resonance could be achieved by changing the spacing between two splits. Additionally, it is experimentally demonstrated that the enhanced toroidal LSSPs resonance is sensitivity to the background medium. The results of our research provide a new idea for exciting the enhanced toroidal dipole.

Dual-sensing and dual-frequency microwave SRR sensor for liquid samples permittivity detection

In this paper, a microwave sensor based on the split ring resonator has been proposed to detect the real part of the dielectric constant of the liquid sample. The proposed structure composed of non-identical double-split ring resonators which are placed in the inner part of the power divider branches. The proposed sensor has two purposes: (1) Measurement of the permittivity of one sample under test in two frequency bands (multi-band), (2) Dual samples under test for simultaneous dielectric detection (multi-sensing). There are several advantages in measuring the permittivity of the sample under test with the proposed sensor such as high Q-factor, high sensitivity, compact size, multi-sensing and multi-band. This paper investigates resonance frequency variation relative to the samples with different permittivities, such as ethanol, methanol, glucose solution and deionized water compared to previous similar works in simulation and experimental results. The permittivity of samples under test varies from 24 to 78 at 25 ˚C, and the simulated sensor resonance frequency would change about from 5.76 to 4.8 GHz at first resonance frequency and 7.85 to 6.35 GHz at second resonance frequency.

Metal-graphene hybrid active chiral metasurfaces for dynamic terahertz wavefront modulation and near field imaging

Chiral metasurfaces can achieve giant chiral optical responses and have been expanded from the optical band to other electromagnetic bands. Here, we propose a new method for dynamic terahertz circular dichroism (CD) manipulation in metasurfaces. By introducing a patterned and electrically doped graphene into the metamirror consists of double layer C-shaped split ring resonators (SRRs), efficient terahertz CD modulation is observed. Since the electrical doping of graphene changes the absorption loss of the metasuface cavity, the structure shows switching between a chiral metasurface and an ordinary metal mirror, which can be seen as "on" and "off" states. The calculation results show an efficient modulation of the terahertz CD in a large dynamic range. In addition, we also use the new method to design two metasurfaces for dynamic terahertz wavefront modulation and near-field digital imaging, both of which show a high-performance electrical switching. This method provides a new way for the design of active terahertz devices based on metasurfaces, and also promotes the applications of terahertz chiral metasurfaces in high-speed wireless communication and dynamic imaging.

Localized breaking of parameter uniformity by macroscopically-negative-permeability metamaterial in low-pressure microwave plasma

Measurements of plasma parameters and transmitted microwaves are performed in a composite of double-split-ring resonators (DSRRs) making magnetic permeability negative and plasmas excited by a 2.45 GHz microwave. We launch the microwave at 100–200 W, modulated by a pulse wave at a low frequency and a low duty ratio to detect time evolutions of plasma parameters. We perform the measurements at different positions with varying distance from the supporting plate of the DSRRs, and find enhanced wave transmission in the composite with non-uniform profiles of electron temperature. To reinforce the measurements of electron temperature, we evaluate the electron energy distribution function (EEDF) by deriving the second deviation of electron current, upon which data smoothing methods are applied, and the estimated EEDF becomes spatially non-uniform with a similar profile to electron temperature. In terms of the validity of results on the enhanced wave transmission, one-dimensional electromagnetic particle simulations reveal sneaking microwaves inside the composite. In comparison with cases of the negative-permeability and the passive (positive-permeability) DSRRs, we confirm that the non-uniformity is attributed to the magnetic resonance of the DSRRs, which is a microscopic effect of the DSRRs to plasma generation, whereas their macroscopic effect makes permeability negative and enhances wave energy transfer inside the composite.

Multifunctional Ultrahigh Sensitive Microwave Planar Sensor to Monitor Mechanical Motion: Rotation, Displacement and Stretch.

This paper presents a novel planar multifunctional sensor that is used to monitor physical variations in the environment regarding distance, angle, and stretch. A double split-ring resonator is designed at 5.2 GHz as the core operating sensor. Another identical resonator is placed on top of the first one. The stacked configuration is theoretically analyzed using an electric circuit model with a detailed parameter extraction discussion. This design is first employed as a displacement sensor, and a compelling high sensitivity of 500 MHz/mm is observed for a wide dynamic range of 0-5 mm. Then, in another configuration, the stacked design is used as a rotation sensor that results in a high sensitivity of 4.5 MHz/ for the full range of 0-180. In addition, the stacked resonator is utilized as a strain detector, and a 0–30% stretch is emulated with a linear sensitivity of 12 MHz/%. Measurements are well in congruence with simulated results, which proves the accurate functionality of the sensor in tracking mechanical deformations, all in a single compact contraption.

Design, modeling, and fabrication of a new compact perfect metamaterial X-band absorber

In this paper, a perfect metamaterial meander line absorber is designed, fabricated, and characterized by a waveguide measurement technique. The proposed metamaterial absorber of a double metal split ring resonator has a single-band absorption response in the microwave region. The characterization and analysis technique of the absorber illustrated a development in its bandwidth value, which minimizes both reflection and transmission coefficients for different upper metal lengths. Simulation and experimental results show that the absorber has a good perfect absorption in the frequency band between 8.5 GHz and 9 GHz. Moreover, the simulation results are in good agreement with the experimental measurements, which verify that this absorber can be used for the radar cross section and any electromagnetic compatibility at the X-band region.