Square Split Ring Resonators Research Articles

A novel multifunctional chiral metasurface with asymmetric transmission

The multiband, multifunctional chiral metasurface with asymmetric transmission exhibits significant potential for diverse applications in modern communication systems, ranging from enhanced signal modulation and polarization control to advanced beam steering and compact antenna design. This research presents a versatile and advanced chiral metasurface operating at multiple bands with diverse functionalities, including asymmetric transmission. The proposed metasurface effectively transforms an incoming Linearly Polarized (LP) wave into a Circularly Polarized (CP) wave. Additionally, it functions as a 90° polarization rotator for the incident LP wave. The design starts with an element of a 2 × 2 supercell comprising a Square Split Ring Resonator (SSRR) and an I-shaped resonator. The right diagonal elements of a supercell undergo scaling down, giving rise to a rotational asymmetry. Chirality is introduced into the design, and cross polarization conversion is enhanced by rotating all four elements by 90° relative to each other. On the back side of the substrate, each element undergoes a 90° rotation compared to its counterpart on the front side, realizing the asymmetric transmission feature. The incorporation of multiband and multifunctional features within a single supercell equips the subject chiral metasurface to be utilized in various engineering applications.

Wideband circularly polarized fractal antenna with SSRR metasurface for 5G applications

In this study, a 3.5 GHz wideband circularly polarised antenna design is presented. The suggested antenna is constructed using square and flower fractal shapes within the patch. The square fractal shapes and flower fractals are implemented inside the slot patch and in the top left and right corners of the patch. The key advantage of using this method is to increase the bandwidth of the antenna besides reduce the size and improve the axial ratio. Then a Square Split Ring Resonator (SSRR) metasurface is added above the antenna for enhancement of gain and back lobe. The metasurface is added on the front of the antenna in order to increase the gain directivity and decrease the sidelobes and back lobe. Using computer simulation software (CST), the proposed metasurface antenna is simulated and then constructed on FR4 substrate with dimensions of (ε_r=4.4 and h=1.6 mm). Operating bandwidth between 1.79 GHz and 5 GHz is achieved, the metasurface antenna's performance attained a fractional bandwidth of 91%. An improved gain of 3.05 dB is observed when metasurface is applied. A measured AR below 3 dB is achieved over the obtained bandwidth. The proposed fractal was reduced in size by 40.43% as compared to conventional antennas. The antenna recommended is suitable for use in the fifth generation (5G) applications.

Influence of Coupled Structural Parameters of Photoconductive Antennas on the Terahertz Narrowband Detection Performance of High Sensitivity and Frequency Selection

Narrowband terahertz (THz) detection plays a key role in biomedical imaging, biological applications, and security screening. Particularly rapid resolution of material differences based on spectral fingerprints or time‐resolved observation of the materials conformational state typically requires only the measurement of spectral information at a few selected frequencies. Here, a high‐performance resonance‐based coupled photoconductive antenna (PCA) was designed, which consists of a square split‐ring resonator (SRR) and an H‐shaped antenna. The incident THz wave energy can be effectively coupled in the gap of the H‐shaped antenna, and the coupling effect base on coupled harmonic oscillator model can be effectively strengthened. By decreasing the square SRR gap width HD, the relative position parameters of d and L3 between the square SRR and H‐shaped antenna can markedly improve the resonance frequency sensitivity with inductive–capacitive resonance. With the square SRR arm length L1 = L2 = L increased, the resonance frequency markedly shifted toward a lower frequency and the resonance sensitivity increased. The results prove that the THz frequency selection detection range of the coupled PCA can be designed to 0.1∼1.0 THz. Compared with the traditional H‐shaped photoconductive detection antenna, the detection resonance peak shifted the lower frequency and the maximum THz detection sensitivity increased by approximately two orders of magnitude at 0.2528 THz. The structure of the noncontact micrometer–coupled PCA is simple and easy to fabricate and integrate. Our findings may also help to advance the use of THz technology in rapid distinguish material properties.

A nested square combination of ε-negative high EMR symmetric metamaterial structure for triple band wireless applications

In this article, a novel metamaterial is presented that is constructed with split ring resonators (SRR) arranged in a nested square configuration. The proposed metamaterial unit cell is constructed over a 1.5 mm thick FR-4 substrate with electrical dimensions of 0.11 λ × 0.11 λ, where λ is the wavelength calculated at 2.8 GHz. The resonating patch contains five interconnected nested squares, including two square split ring resonators (SSRRs). The unit cell exhibits three distinct frequencies at 2.8 GHz, 5.8 GHz, and 11.2 GHz, with corresponding magnitudes of −45 dB, −50 dB, and −30 dB, respectively. Negative permittivity (ε-Negative) is observed in frequency ranges of 2.3–3.20 GHz, 4.4–6.9 GHz, and 10.8–11.30 GHz, with near-zero refractive index. The simulated outcome acquired in CST microwave studio is subsequently confirmed using analogous circuit modeling in Advanced System software (ADS). Moreover, the prototype of the proposed metamaterial is developed that shows similar resonances obtained in the simulation. The effective medium ratio (EMR) of the unit cell is calculated and a high EMR of 8.3 expresses the compactness of the metamaterial. Due to its structural compactness, this new metamaterial with ε-negative, near zero refractive index, and triple band resonance properties holds significant potential for wireless applications such as radar systems, satellite communications, and wireless sensor networks.

Minimal microfluidic metamaterial sensor for concentration detection

The design of high sensitivity and minimal size sensors for liquid concentration detection has significant importance in biomedical and chemical engineering. In this paper, we present a microfluidic liquid sensor for concentration detection based on metamaterial, with a minimal size of 20 × 16 mm2. The sensor consists of a modified square split-ring resonator (SRR) and a microstrip transmission line (MTL), integrated with a microfluidic device. The operating frequency of the sensor is 4.38 GHz. Experimental results demonstrate that the resonant frequency of the water–ethanol mixture with concentrations ranging from 0 to 100 % has a linear shift of 290 MHz. A mathematical model is established by examining the relationship between the transmission parameters and the complex dielectric constant, the maximum deviation between the ethanol solution concentration predicted by this model and the actual concentration is 0.5 %. The sensor exhibits a sensitivity of 2.14 × 10^-3 dB/(mg/dL) to aqueous glucose solutions with 0–––400 mg/dL. A fitting formula is derived from the transmission parameters to predict unknown concentrations of aqueous glucose solutions, could detect the change of 1 mg/dL glucose solution accurately with a maximum error of 0.7 %.

Near zero index Metamaterial-based SIW antenna for 6G Sub-Terahertz applications

This paper introduces a novel high-gain circularly polarized (CP) antenna that utilizes a NRZI (Near Zero Refractive Index) and MNG (Mu Negative) metamaterialslab. The antenna employs a substrate integrated waveguide (SIW) technique and loaded with compact square split ring resonator (SSRR) combined with a hexagonal-shaped structure by a 0.2 mm width slab as a unit cell to achieve high gain and circular polarization. The metamaterial characteristics were examined through material wave propagation in two main directions at the y and x-axis. For wave propagation at the y-axis, the MTM structure demonstrates mu-near-zero (MNZ) with more than 88 GHz bandwidth, NZRI, and Epsilon-Near-Zero (ENZ) properties. However, for x-axis wave propagation, it indicates a wide negative range of single mu metamaterial from 176 to 220 GHz, NZRI, and ENZ properties. By using six unit cells, the antenna acts as an aperture-efficient focusing metasurface lens and polarization converter for a primary source antenna. The NRZI-MNG enhances the gain of the suggested antenna by 6–7 dB, and converts the linearly polarized wave emitted by the patch antenna into circularly polarized waves. The designed antenna has an impedance bandwidth from 176.5 to 285 GHz, with a 3 dB axial ratio achieved from 177 to 204 GHz. The peak gain of the antenna is 11.3 dBi at 223 GHz, and a gain of around 10 dBi is achieved over the entire CP bandwidth with a good cross-polarization level. In addition, the transmittance of the suggested metamaterial antenna is between 80% and 90% in the operating band. These excellent performances make this antenna very promising for sub-THz 6G applications.

Planar Microwave Sensor with High Sensitivity for Material Characterization Based on Square Split Ring Resonator (SSRR) for Solid and Liquid

Microwave resonator sensors are the most extensively used sensors in the food industries, quality assurance, medical, and manufacturing. Planar resonant technique is chosen as the medium for characterizing dielectric properties of material due to its compact in size, low cost and easy to fabricate. But these techniques have a low Q-factor and little sensitivity. This work uses the perturbation approach to overcome this technique's flaw, which is that Q-factor and resonant frequency are affected by the resonator's dielectric properties. This suggested sensor operated at 2.5GHz between 1GHz and 4GHz for material characterisation of solid and liquid samples. These sensors were constructed on a substrate made of RT/Duroid Roger 5880, which has a copper layer that is 0.0175 mm thick and has a dielectric constant of 2.2. This square split ring resonator (SSRR) sensor thus generates narrower resonant, low insertion loss, and a high Q-factor value of 430 at 2.5GHz. The SSRR sensor's sensitivity is 98.59%, which is higher than that of past studies. The application of the suggested sensor as a tool for material characterisation, particularly for identifying material attributes, is supported by this findings.

Split ring resonator inspired defected ground plane dual operating band antenna for wireless LAN and RFID applications

Defected ground structure (DGS) using an array of the three split ring resonators inspired antenna for the Wireless Local Area Network(WLAN) and RFID sensor is proposed in this manuscript. The complete physical measurement for the proposed antenna is 50 X 40 mm2 (at lower operating frequency). The defected ground plane structure along with the inclusion of the square split ring resonators (SRRs) in the ground plane helps in gain and bandwidth improvement. 1 × 3 split ring resonator array is used to make the existing ground plane to be defected. The cost effective FR – 4 materials is used as a substrate for the fabrication with the standard thickness of 1.6 mm. The resonance frequencies are at 2.4 and 5.8 GHz having the average gain 2.65dBi. The impedance bandwidths for both the frequencies are 5.0 % (2.31 to 2.49 GHz) and 3.9% (4.9 to 6.1 GHz). The dipole and omni directional radiation patterns, overall gain and efficiency of around 75% make the antenna most practically possible for the RFID and WLAN devices.

Triple-Band Square Split-Ring Resonator Metamaterial Absorber Design with High Effective Medium Ratio for 5G Sub-6 GHz Applications

This article proposes a square split-ring resonator (SSRR) metamaterial absorber (MMA) for sub-6 GHz application. The unit cell of the MMA was designed and fabricated on commercially available low-cost FR-4 substrate material with a dielectric constant o 4.3. The higher effective medium ratio (EMR) of the designed unit cell shows the compactness of the MMA. The dimension of the unit cell is 9.5 × 9.5 × 1.6 mm3, which consists of two split rings and two arms with outer SSRR. The proposed MMA operates at 2.5 GHz, 4.9 GHz, and 6 GHz frequency bands with a 90% absorption peak and shows a single negative metamaterial property. The E-field, H-field, and surface current are also explored in support of absorption analysis. Moreover, the equivalent circuit model of the proposed MMA is modelled and simulated to validate the resonance behavior of the MMA structure. Finally, the proposed MMA can be used for the specific frequency bands of 5G applications such as signal absorption, crowdsensing, SAR reduction, etc.

Tunable Cross-Coupled metallic elements loaded epsilon negative and Near-Zero index characteristics based metamaterial

This study examines epsilon-negative (ENG) and near-zero index (NZI) tunable cross-coupled (TCC) metamaterial (MTM) unit cells for multi-band wireless communications. The square split ring resonator (SSRR), a cross-coupled metallic element, and a star-like shape are added at the center of the resonator. The EMR value is 10.24, representing the proposed structure's compactness. The tunability characteristics are investigated by varying the cross-coupled nearby metallic element length within the frequencies of 3.38–3.44 GHz, 7.53–8.0 GHz, and 10.24–10.79 GHz. The NZI characteristics are observed within the frequencies of 3.40–4.66 GHz, 7.41–7.75 GHz, and 10.17–10.31 GHz, respectively, while the ENG characteristics are observed at 2.61–5.15 GHz, 6.43–8.23 GHz, and 9.28–10.45 GHz, respectively. The bandwidth of the designed TCC MTM unit cell is 2.49–4.00 GHz, 6.89–7.83 GHz, and 9.75–10.64 GHz, respectively. The tunability, ENG, and NZI characteristics with a high EMR value enable it for critical microwave applications, including S, C, and X frequency bands. The anticipated structure may be a good candidate for enhancing the gain and bandwidth of the antenna and filter designs and operations, as well as frequency stability and efficiency for multi-band wireless communications.

Design and Analysis of Polarization-Independent, Wide-Angle, Broadband Metasurface Absorber Using Resistor-Loaded Split-Ring Resonators

Metasurface (MS) absorbers with polarization-insensitivity and wide-angle reception features have attracted much attention due to their unique absorption property. A polarization-insensitive broadband MS absorber structure, having wide-angle reception based on square split-ring resonators (SSRRs) and loaded with lumped resistors, is proposed in this paper. The proposed MS unit cell consists of a fixed-thickness FR4 dielectric substrate and a variable air-thickness substrate. The simulation results show that the proposed MS absorber is stable across a wide angular range for both normal and oblique incidences. Furthermore, the simulated results show that some parameters, such as unit-cell geometry and lumped resistors, can be varied to improve the performance of the MS absorber. The experimental results indicate that the proposed MS absorber can be achieved an absorption higher than 90% across the frequency range from 1.89 GHz to 6.85 GHz with a relative bandwidth of 113%, which is in agreement with simulation results. Thus, the proposed MS absorber can be more suitable in RF energy harvesting or wireless power transfer applications.

Quad-Band Polarization-Insensitive Square Split-Ring Resonator (SSRR) with an Inner Jerusalem Cross Metamaterial Absorber for Ku- and K-Band Sensing Applications

The development of metamaterial absorbers has become attractive for various fields of application, such as sensing, detectors, wireless communication, antenna design, emitters, spatial light modulators, etc. Multiband absorbers with polarization insensitivity have drawn significant attention in microwave absorption and sensing research. In this paper, we propose a quad-band polarization-insensitive metamaterial absorber (MMA) for Ku- and K-band applications. The proposed patch comprises two square split-ring resonators (SSRR), four microstrip lines, and an inner Jerusalem cross to generate four corresponding resonances at 12.62 GHz,14.12 GHz, 17.53 GHz, and 19.91 GHz with 97%, 99.51%, 99%, and 99.5% absorption, respectively. The complex values of permittivity, permeability, refractive index, and impedance of MMA were extracted and discussed. The absorption mechanism of the designed MMA was explored by impedance matching, equivalent circuit model, as well as magnetic field and electric field analysis. The overall patch has a rotational-symmetrical structure, which plays a crucial role in acquiring the polarization-insensitive property. The design also shows stable absorption for both transverse electric (TE) and transverse magnetic (TM) modes. Its near-unity absorption and excellent sensing performance make it a potential candidate for sensing applications.

Structural, dielectric, and magnetic properties characterization of sol–gel synthesized CaxZn(0.90-x)Ni0.10Fe2O4 nanopowder and its application as flexible microwave substrate with polarization-insensitive SNG metamaterial

In this work, CaxZn(0.90-x)Ni0.10Fe2O4 nanopowder-based new flexible microwave substrates are prepared using the sol–gel method for metamaterial applications. Three different x values are chosen as x = 25, 50, 75 and termed as Ca25, Ca50, and Ca75 respectively. The structural and morphology of synthesized materials are investigated with XRD and FESEM analysis. The dielectric properties were also determined and the obtained values for dielectric constant (εr) and loss tangents (Tδ) are ranges from 3.25 to 4.25 for εr and 0.0025 to 0.0065 for Tδ for Ca25, Ca50, and Ca75 respectively. In addition, the magnetic permeability μr and magnetic loss tangent (Tδm) values are estimated from the scattering parameters S11 and S21 obtained by using Agilent module 85071E, and the achieved values of μr and Tδm are ranges from 0.875 to 1.00 and 0.0035 to 0.0075 respectively. Later, the proposed metamaterial unit cell consists of a square split ring resonator (SSRR) and a circular SRR (CSRR) loaded with a plus shape is designed and fabricated on the proposed flexible substrates obtained from the synthesized CaxZn(0.90-x)Ni0.10Fe2O4 nanopowders to validate their application as metamaterials. The novelty of the proposed work is found in the unit cell being polarization-insensitive and having a multiband, low electrical dimension that improves the EMR, single-negative characteristics with high flexibility and lightweight and suitable for C, X, and Ku bands of microwave regime.

An angular stable triple-band anisotropic cross-polarization conversion metasurface

This study presents a thin triple-band cross-polarization-conversion metasurface (CPCM) comprising square split-ring resonators (SSRR), metallic cross elements where four metal strips are housed inside the SSRR. The SSRR resonator and back-layer are designed with copper on FR-4 substrate, where substrate sandwiches the resonator and the back-layer. The SSRR and metallic cross elements are developed on a dielectric substrate and the backside block by a copper layer. CST MWS 2018 is used to design and perform analysis of the metasurface. The electrical dimension of the CPCM structure is 0.128 λ × 0.128 λ × 0.044 λ at a lower frequency of 5.49 GHz. The CPCM achieved a bandwidth of 5.35 to 5.69 GHz, 7.60 to 8.76 GHz, and 12.41 to 13.96 GHz covering the S, C, and X frequencies band. Moreover, the simulated result of the CPCM is verified through experimental development. An electrically thin substrate makes the proposed structure identical in polarization responses (up to 750) at normal and oblique incidents above the mentioned frequency band. The surface current distribution is analyzed to comprehend the structural mechanism behind the polarization conversion of the unit cell.

Ultra-thin reflective linear and circular polarization converter for Ku band applications

In this study, metasurface-based ultra-thin reflective polarization converter is offered. The proposed converter acts as a hybrid converter, providing both linear and circular polarization. The design consists of periodically arranged square split ring resonator (SRR) that is made by subtracting two circular segments and a full circle. In addition, commercially more easily accessible FR-4 material was used as substrate in the design. The metasurface converter operate in Ku frequency band range from 12.05 to 17.9 GHz for both linear to linear polarization and circular to circular polarization with over 90 percent polarization conversion rate (PCR) performance under normal incidence. Oblique angle PCR performance is up to 45 degrees with 80 percent conversion ratio at the same bandwidth of the proposed design. In addition, the proposed converter provide linear to circular polarization conversion (left-handed circular polarization-LHCP) range from 11.3 GHz to 11.5 GHz. The converter has a very competitive structure with a thickness of only 1.2 mm (0.06 λ) and the performance of the design has been compared with other studies with its superior aspects in the literature.

A Beam-Split Metasurface Antenna for 5G Applications

This article presents a hybrid metasurface split beam antenna for fifth-generation (5G) mobile applications at 3.5 GHz. Multi-beam antennas with high directivity are required for a 5G mobile network. It can be achieved by having an array antenna. Using an antenna array at low frequency increases the complexity and size of the whole network. Therefore, a metasurface (MS) is proposed to direct surface current and to have high gain and multibeam properties. To achieve that, a square split ring resonator (SSRR) and U-shaped unit cell metasurface is implemented as a superstrate to a single square patch antenna. The manipulation of this hybrid metasurface configuration can create opposite current flow on the unit cell and thus split the beam. The hybrid metasurface superstrate and antenna are fabricated on FR-4 ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varepsilon \text{r}\,\,=4.4$ </tex-math></inline-formula> , tan <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\delta =0.02$ </tex-math></inline-formula> ). Results show that the antenna resonates well at 3.5 GHz, with a less than −10 dB reflection coefficient. The arrangement of the unit cells on the superstrate metasurface is able to split the current, and thus the radiation pattern beam is split into two beams in the E-plane at ± 45°. This antenna is a good candidate for future 5G Pico cell base stations in urban or suburban areas with high capacity and interferences.

Estimating the frequency and bandwidth of square-split ring resonator (S-SRR) designs via support vector machines (SVM)

In this study Support Vector Machine (SVM) based estimation technique is proposed for estimating the bandstop frequency and bandwidth of square-split ring resonators. Artificially engineered surfaces especially the planar frequency selective surfaces like the SRRs have narrowband properties so that estimating the filtering frequencies and the bandwidth is essential in a cost and design-effective way. The proposed method, which is superior to optimization methods and 3D electromagnetic solvers in terms of cost and computational burden, achieved accurate results via SVMs generalization capability. This study represents two SVM regression models one for predicting frequency and the other for predicting bandwidth having fast response and accuracy. Results of the proposed model reveal that resonance frequency estimation error, in terms of percentage, is bounded in the interval [0.0542, 3.5938], with an overall error of 0.89 % for the test data. The mean and standard deviation of the percentage error is obtained as 0.9861 and 0.9376, respectively. In addition to that -10dB bandwidth is estimated with the bounded error where estimation error in terms of percentage would be lie in the interval [0.068925, 6.876800] with an overall error of 3.68% for the test data.

Theoretical approach to verify the resonance frequency of a square split ring resonator

An analytical model for a square split ring resonator (S-SRR) having a single split-gap is considered here to reliably estimate the fundamental resonance frequency of the ring. An S-SRR is assumed to be equivalent to a series-resonant LC loop. The approximate formulas for equivalent self-inductance and total capacitance of the ring are derived separately. The total capacitance of the ring is expressed as a sum of a gap capacitance and a surface capacitance (which is associated with charges on the SRR walls). Both the capacitances are influenced by not only the medium in split-gap but also the dielectric constant of substrate. These are taken care of by including appropriate weight factors in the expressions for the capacitances. Again, using the software CST Microwave Studio, the resonance frequencies are calculated for several values of split-gap and SRR side length. Then the results of simulation are compared with the results obtained from our formula. It is found that simulation results agree quite well with the analytical results. Also, the analytical result for resonance frequency of SRR shows good agreement with a previously published experimental result. This model can be used for studies of the resonant properties of split rings in the microwave and terahertz regions.

Modelling of metallic inclusions on non-homogeneous dielectric substrates

ABSTRACT In this article, modelling is done for Square Split Ring Resonators (SSRR) as a quasi-static equivalent circuit in a non-homogeneous environment. The authors propose a new relationship for the relative permittivity for a metallic inclusion etched on top of a dual substrate in a non-homogeneous medium. The stacking sequence of the substrates plays a vital role in the response of the SSRR. This paper highlights the change brought about by the dielectric materials’ stacking order on resonant frequency and quality factor. The analytical and numerical study of SSRR etched on the dual substrates shows a good correlation of values. A comparative study indicates a better fit of the proposed formula for the effective permittivity over the conventional averaging method. This article highlights the advantages of using a dual substrate material for fabricating metamaterial structures for different applications. The advantage of the proposed permittivity equation is its applicability to all kinds of geometries. Three different substrate materials were used for the performance study of the SSRR (FR4, Rogers RT/Duroid 5880 and Alumina).

A multiband patch antenna with embedded square split ring resonators in non-Homogeneous substrate

The authors have attempted to influence an embedded square split ring resonator (SSRR) response in a stacked non-homogeneous substrate to demonstrate a quad-band antenna. The purpose is to produce multiband operations of a microstrip patch antenna. The highlighted factor is the effect of embedding an SSRR and the differing relative permittivity of the substrate on the side length of the SSRR. The analysis shows that a non-homogeneous dual substrate patch produces multiple bands compared to a single substrate patch antenna without any parameter change. A dual substrate antenna fabricated using FR4 and Rogers RT/Duroid 5880 copper clad sheets with a dimension of 85.6x54x0.908 mm3 (0.314λ0x0.198λ0x0.003λ0). The antenna resonates at 1.1, 2.45, 3.65 and 5.25 GHz in the L-, S- and C-bands. It is possible to employ the patch antenna in WLAN (dual-band) and WiMAX applications and suitable for mobile broadcast service at 1.1 GHz. The authors compare the simulated and measured results of a prototype in the article. The maximum measured gain is 5.48 dBi at 1.1 GHz and 4.025 dBi at 3.65 GHz. The measured bandwidth is 60 MHz (1.2%) at 5.25 GHz.