Split Ring Resonator Research Articles

Highly selective filtering power divider using substrate integrated waveguide technique for radar applications

<p><span>This article exhibits a filtering power divider designed with substrate integrated waveguide (SIW) technique, having the power dividing as well as filtering functionalities. In the design band-pass performance is realized by merging SIW structure having high-pass response and complementary split ring resonator (CSRRs) with parallel tank LC resonant response and the dumbbells shape defected ground structure (DGS) with high out of band rejection characteristics. The anticipated structure serves as both a power divider and a filter, it reduces both the cost and the size of the system. Structure is constructed and tested to confirm the design functionality. The measurement result shows the return loss of -25.94 dB with 3-dB fractional bandwidth of 2.85% at 14 GHz.</span></p>

Evaluation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) using a high figure-of-merit plasmonic multimode refractive index optical sensor

In recent years, following the outbreak of the COVID-19 pandemic, there has been a significant increase in cases of SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2) and related deaths worldwide. Despite the pandemic nearing its end due to the introduction of mass-produced vaccines against SARS-CoV-2, early detection and diagnosis of the virus remain crucial in preventing disease progression. This article explores the rapid identification of SARS-CoV-2 by implementing a multimode plasmonic refractive index (MMRI) optical sensor, developed based on the split ring resonator (SRR) design. The Finite Difference Time Domain (FDTD) numerical solution method simulates the sensor. The studied sensor demonstrates three resonance modes within the reflection spectrum ranging from 800 nm to 1400 nm. Its material composition and dimensional parameters are optimized to enhance the sensor’s performance. The research indicates that all three resonance modes exhibit strong performance with high sensitivity and figures of merit. Notably, the first mode achieves an exceptional sensitivity of 557 nm/RIU, while the third mode exhibits a commendable sensitivity of 453 nm/RIU and a Figure of Merit (FOM) of 45 RIU−1. These findings suggest that the developed MMRI optical sensor holds significant potential for the early and accurate detection of SARS-CoV-2, contributing to improved disease management and control efforts.

Symmetric CRLH-TL filter based dual band microstrip antenna design approach

This paper presents a novel filter-based analysis for the conventional rectangular patch antenna (RPA) using the Composite Right/Left-Handed Transmission Line (CRLH-TL) theory. We introduce two circuit models for RPA, described by lumped components and transmission line (TL) elements. An RPA is considered a Symmetric CRLH-TL (SCRLH-TL). We validated the analysis by comparing the circuit model and full-wave analysis simulation results. The TL circuit model error in the full-wave analysis was less than 5%. A dual-band Zeroth-Order Resonant (ZOR) antenna is designed and manufactured based on the introduced Lumped element circuit model, which exhibits filtering characteristics in both bands. We obtain the antenna circuit model by incorporating the RPA lump circuit model with LC resonators. We implemented the antenna structure by combining the RPA and complementary split-ring resonators (CSRR) modeled by the LC resonators. We initialized the antenna center frequency bands for WiMAX 2.45 GHz and 3.60 GHz. The CSRRs control the configuration of the center frequencies. The simulation and measured results are in good agreement. The proposed antenna dimensions are 0.66×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document}0.66×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document}0.012 λg\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\lambda _g$$\\end{document} at 2.45 GHz (43.22×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document}43.22×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document}0.81 mm3). The measured gains are 3.47 dB and 4.64 dB for 2.45 GHz and 3.60 GHz, respectively. Two radiation nulls were observed at 2.09 GHz and 2.98 GHz for the 2.45 GHz band and one radiation null at 3.45 GHz for the 3.60 GHz band. Also, the fractional bandwidth is 4.03% and 1.39%, respectively. The radiation pattern is nearly omnidirectional. The simulated efficiency is 90% for 2.45 GHz and 87% for 3.60 GHz frequency bands.

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.

Wireless image transfer by various antennas using transmitter and receiver modules at 5.8 GHz

Abstract This research proposes an inexpensive technique for wireless image transfer for security and surveillance applications. The technique uses a 5.8 GHz transmitter and receiver module, along with external antennas in the real-time image transfer within a radius of 100 m. The transferred images are stored in a laptop using a Python code-based graphical user interface application. Different antennas, dipole, circular split-ring resonators, hexagonal split-ring resonators, and metamaterial antennas are utilized for comparison. The Blind/Referenceless Image Spatial Quality Evaluator method is used to assess the picture quality of transferred images to quantify image transfer performance when no ground truth or reference photos are supplied. According to the presented results, images transferred using metamaterial antennas have higher quality than those transferred with other types of antennas. For security considerations, such a system can communicate and store the images in real time.

A novel miniaturized microstrip filtering power divider with high selectivity based on composite right/left-handed (CRLH) concept

Abstract This paper proposes a compact microstrip filtering power divider (FPD) with high selectivity and equal power division ratios based on the composite right/left-handed (CRLH) concept. The proposed equal microstrip FPD is designed by cascading two CRLH unit cells and a grounded via hole. The proposed CRLH unit cell is realized by an interdigital capacitor loaded between two transmission lines (TL) on the upper metal layer and the fractal/meander complementary split-ring resonator (FMCSRR) on the ground plane. The grounded via hole has been used to improve frequency selectivity and out-of-band rejection of the proposed microstrip FPD. The equivalent circuit model compared with full-wave simulation results of the proposed microstrip FPD has been provided. The proposed microstrip FPD has been fabricated and measured, and a good agreement has been found between the simulation and measurement results. The proposed microstrip FPD has a passband covering 2.38–2.45 GHz, and its measured 3 dB fractional bandwidth is about 2.9 %. The total size of the proposed microstrip FPD is 0.17 λ g × 0.07 λ g. Compared with other reported FPDs, the presented microstrip FPD has many advantages like compact size, low loss, easy fabrication, extremely sharp rejection skirts around the desired passband and high selectivity.

Magnetic-field controlled on-off switchable non-reciprocal negative refractive index in non-Hermitian photon-magnon hybrid systems

Photon-magnon coupling, where electromagnetic waves interact with spin waves, and negative refraction, which bends the direction of electromagnetic waves unnaturally, constitute critical foundations and advancements in the realms of optics, spintronics, and quantum information technology. Here, we explore a magnetic-field-controlled, on-off switchable, non-reciprocal negative refractive index within a non-Hermitian photon-magnon hybrid system. By integrating an yttrium iron garnet film with an inverted split-ring resonator, we discover pronounced negative refractive index driven by the system’s non-Hermitian properties. This phenomenon exhibits unique non-reciprocal behavior dependent on the signal’s propagation direction. Our analytical model sheds light on the crucial interplay between coherent and dissipative coupling, significantly altering permittivity and permeability’s imaginary components, crucial for negative refractive index’s emergence. This work pioneers new avenues for employing negative refractive index in photon-magnon hybrid systems, signaling substantial advancements in quantum hybrid systems.

Enhanced Antipodal Vivaldi Antenna with SSRR metamaterial for improved 5G performance in the 38 GHz band

This study involves the integration of a compact Antipodal Vivaldi Antenna (AVA) with a square-shaped split ring resonator (SSRR) metamaterial to achieve improved performance, specifically in the 38 GHz band of 5G applications. The compact antenna is fabricated on Roger's substrate 5880 with 20 x 6 x 0.5 mm3 dimensions. The operational frequency ranges from 34 GHz to 43.8 GHz, catering to the specific needs of the 5G spectrum. To optimize the antenna's performance, corrugations are strategically introduced in the flares of the AVA, resulting in a notable improvement in the front-to-back ratio (FBR) by 18.35 dB. Additionally, square-shaped split ring resonators (SSRRs) are integrated into the AVA aperture, contributing to a gain enhancement of 4.6 dBi. The overall design achieves a gain ranging from 9.2 dBi to 10.4 dBi across the 38 GHz frequency band. The proposed AVA demonstrates good characteristics, with the highest front-to-back (FBR) value recorded at 20.4 dB at 40.6 GHz. The FBR consistently exceeds 15.6 dB throughout the specified frequency range. The antenna design is fabricated, simulated, and experimentally verified, affirming its suitability for compact 5G devices. The results indicate that the proposed miniaturized AVA, incorporating SSRR metamaterial and optimized flare corrugations, is an efficient candidate for compact 5G devices, offering enhanced gain and FBR over the desired frequency band.

A Novel Microwave Imaging Approach Using Rectangular Antenna with Complementary Split-Ring Resonator

A Novel Microwave Imaging Approach Using Rectangular Antenna with Complementary Split-Ring Resonator

Excitation of high-quality quasi-BIC toroidal mode in a lattice perturbed terahertz metasurface

The bound state in continuum (BIC) is a phenomenon that describes the existence of nonradiative modes (dark modes) embedded in the continuum frequency range. However, an ideal BIC cannot be detected experimentally. The BIC can be transformed into a quasi-BIC by establishing a leaky channel to the radiation continuum. In this study, instead of the conventional asymmetric split ring resonator structure, a sharp quasi-BIC mode is excited in a symmetric split ring resonator (SRR) metasurface by the perturbation of the lattice constant of the unit cell via changing the interspacing distance between two adjacent SRRs. The quality factor of the quasi-BIC mode can be tuned by varying the interspacing of two SRRs, while the resonance frequency of the quasi-BIC mode remains stable. An eigenmode analysis confirms the presence of the quasi-BIC mode, while the ab initio Fano theory and a coupled oscillator model elucidate the radiative and nonradiative coupling mechanisms. The influence of geometric perturbations on the quasi-BIC mode is quantitatively assessed through the extracted fitting parameters, providing insights into the transition from the dark mode (ideal BIC) to the quasi-BIC mode. The terahertz time domain spectroscopy measurement demonstrates a signature of the quasi-BIC resonance mode as a result of the band folding in the first Brillouin zone induced by the doubling of the lattice constant.

A reconfigurable transmitarray unit cell employing liquid metal

AbstractIn this paper, a reconfigurable transmitarray unit cell using liquid metal is presented. It consists of three conducting layers where the geometries of the resonators, on the different layers, differ and consist of an arrow shape together with rotated split rings. The arrow‐shaped conducting layer has the capability to convert the polarization of the incoming waves by 90°. The split ring resonators, on the upper and lower conducting layers, have the same dimensions but different orientations (horizontal and vertical polarization). Several fluidic channels are placed beneath/above the conducting layers. The transmission behaviour of the unit cell can be changed by altering the geometrical parameters which is achieved by injecting the liquid metal into the channels. More than 300° phase shift range with a maximum S21 of ∼ −1.5 dB at 3.3 GHz is obtained. It exhibits 3 dB of insertion loss over a bandwidth ranging from 3.2 to 3.43 GHz. It is the first time that a transmitarray unit cell, reconfigured employing liquid metal, provides a combination of low insertion loss and large phase shift range. The proposed prototype was fabricated and measured within an open‐ended waveguide and the measured results agree well with the simulations and verify the effectiveness of the design. The reconfigurable transmitarray unit cell can be used to design beam‐scanning arrays, as well as for applications in wireless communications.

Electrically switchable behavior in coupled EIT-like meta-molecule and Fabry-Pérot cavity

In this paper, we propose a microstrip Fabry–Pérot (FP) cavity embedded with an active electromagnetically-induced-transparency-like (EIT-like) meta-molecule to investigate the electrically switchable behavior. The phenomenon of EIT is achieved by coupling a ‘bright’ comb-line resonator with a ‘dark’ split-ring resonator. The FP cavity is fabricated by etching two narrow slots on a microstrip line. With two different resonance mechanisms working together, the proposed composite EIT-cavity design is shown to exhibit the enhanced EIT-like transmission characteristics, accompanied by two sharp Fano-type line-shapes. By incorporating PIN diodes into the composite EIT-cavity structure, we can dramatically modulate the transmission spectrum via external DC voltage. In particular, we show the multi-band unity modulations through biasing the proposed active samples. Moreover, the slow light on-to-off switching processes are also obtained with modifying the state of PIN diode from dielectric to conductive. Our results may open important opportunities for fabricating dynamic functional photonic devices in the future.

Mechanism insights for impedance matching in split-ring resonator topologies under bio-medical scenarios

The utilization of microwave radiation has gained increasing importance in various biological applications. However, a significant challenge remains in the interaction between the microwaves and the human skin, primarily due to the impedance mismatch. Recently, the employment of split-ring resonator (SRR) topologies has become increasingly prevalent for addressing such a problem. Despite this, most existing literatures lack a comprehensive understanding of the underlying mechanisms. In this study, we follow Babinet’s principle and numerically study the dispersion relations of a single-split-ring resonator (S-SRR) and its complementary topology, single-complementary-split-ring resonator (S-CSRR). We focus on conducting the impedance analysis, along with far-field and near-field excitation characterizations. The results indicate that S-CSRR ensures an improved impedance matching, thereby significantly enhancing microwave power flow within the bio-tissue. A 2 × 2 array of S-CSRR is experimentally examined for validation. We demonstrate that the S-CSRR array enhances the total specific absorption rate (SAR) of a deeply-implanted-tumor-phantom by a factor of 1.95. Our work may provide a broader understanding towards impedance matching, which may facilitate the design of more efficient diagnostic tools in bio-medical field.

High-Gain Multi-Band Koch Fractal FSS Antenna for Sub-6 GHz Applications

This study introduces a novel antenna based on the binary operation of a modified circular patch in conjunction with the Koch fractal. The antenna is intended for applications in the sub-6 GHz band, partial C-band, and X-band. The low-cost antenna is fabricated on a 1.6-mm-thick FR-4 substrate. A frequency-selective surface (FSS) is used to overcome the decreased values of the gain and bandwidth due to the fractal operations. The introduced split ring resonator (SRR) and the antenna substrate dimension reduction reduce the bandwidth and antenna gain. The air gap between the FSS and the antenna not only enhances the antenna gain but also controls the frequency tuning at the design frequency. The antenna size is miniaturized to 36.67%. A monopole antenna ground loaded with an SRR results in improved closest tuning (3.44 GHz) near the design frequency. The antenna achieves a peak gain of 9.37 dBi in this band. The FSS-based antenna results in a 4.65 dBi improvement in the gain value with the FSS. The measured and simulated plots exhibit an excellent match with each other in all three frequency bands at 2.96–4.72 GHz. These bands cover Wi-MAX (3.5 GHz), sub-6 GHz n77 (3300–3800 MHz), n78 (3300–4200 MHz), and approximately n79 (4400–4990 MHz), in addition to C-band applications.

Wireless neuromodulation at submillimeter precision via a microwave split-ring resonator.

A broad spectrum of electromagnetic waves has been explored for wireless neuromodulation. Transcranial magnetic stimulation, with long wavelengths, cannot provide submillimeter spatial resolution. Visible light, with its short wavelengths, suffers from strong scattering in the deep tissue. Microwaves have centimeter-scale penetration depth and have been shown to reversibly inhibit neuronal activity. Yet, microwaves alone do not provide sufficient spatial precision to modulate target neurons without affecting surrounding tissues. Here, we report a split-ring resonator (SRR) that generates an enhanced microwave field at its gap with submillimeter spatial precision. With the SRR, microwaves at dosages below the safe exposure limit are shown to inhibit the firing of neurons within 1 mm of the SRR gap site. The microwave SRR reduced seizure activity at a low dose in both in vitro and in vivo models of epilepsy. This microwave dosage is confirmed to be biosafe via histological and biochemical assessment of brain tissue.

Experimental study on the location detection method of deionized water freezing front based on microwave resonance theory

Ice accumulation is a natural phenomenon in cold climates, but it causes serious issues to various industries. To accurately detect the thickness of ice on a horizontal cold plate, a capacitance-coupled split-ring resonator is employed. The impact of the average height of static and dynamic freezing front on the resonator at −20 °C was investigated experimentally. The sensor is capable of detecting freezing fronts up to a maximum height of approximately 20 mm. The height of the static freezing front can be sensitively detected within the range of 0–5.4 mm, with an average error of the sensor less than 0.53 mm. Furthermore, the height of the dynamic static can be detected with a higher degree of accuracy within 0–8.4 mm, the average detection error is 0.37 mm. This technology can serve as a point of reference for the field of anti-icing.

An Electrically Small Patch Antenna Sensor for Salt Concentration Measurement of NaCl Solution.

In this paper, a complementary split-ring resonator (CSRR)-based patch antenna is proposed as a microwave sensor to measure the salt concentration of NaCl solution. The microwave sensor consists of an RF-4 substrate, where a small copper disc is attached on the top as the radiator, a larger copper disc integrated with two CSRRs is attached on the bottom side as the finite ground plane, and a coaxial feeding port is introduced at the ground plane center. During salt concentration sensing, only the top disc is immersed into NaCl solution. The results indicate that the proposed microwave sensor can measure salt concentrations ranging from 5‱ to 35‱ with a maximum sensitivity of 0.367 (kHz/(mg/L)). The proposed microwave sensor is low-cost, low-profile, electrically small, lightweight, and easy to fabricate, and it also can be applied to other solutions' concentration sensing.

Small-Size Eight-Element MIMO Metamaterial Antenna with High Isolation Using Modal Significance Method.

This article presents a symmetrical reduced-size eight-element MIMO antenna array with high electromagnetic isolation among radiators. The array utilizes easy-to-build techniques to cover the n77 and n78 new radio (NR) bands. It is based on an octagonal double-negative metamaterial split-ring resonator (SRR), which enables a size reduction of over 50% for the radiators compared to a conventional disc monopole antenna by increasing the slow-wave factor. Additionally, due to the extreme proximity between the radiating elements in the array, the modal significance (MS) method was employed to identify which propagation modes had the most impact on the electromagnetic coupling among elements. This approach aimed to mitigate their effect by using an electromagnetic barrier, thereby enhancing electromagnetic isolation. The electromagnetic barriers, implemented with strip lines, achieved isolation values exceeding 20 dB for adjacent elements (<0.023 λ) and approaching 40 dB for opposite ones (<0.23 λ) after analyzing the surface current distribution by the MS method. The elements are arranged in axial symmetry, forming an octagon with each antenna port located on a side. The array occupies an area of 0.32 λ2 at 3.5 GHz, significantly smaller than previously published works. It exhibits excellent performance for MIMO applications, demonstrating an envelope correlation coefficient (ECC) below 0.0001, a total active reflection coefficient (TARC) lower than -10 dB for various incoming signals with random phases, and a diversity gain (DG) close to 20 dB.

Active control of terahertz quasi-BIC and asymmetric transmission in a liquid-crystal-integrated metasurface

Quasi-bound states in the continuum (quasi-BICs) offer an excellent platform for the flexible and efficient control of light-matter interactions by breaking the structural symmetry. The active quasi-BIC device has great application potential in fields such as optical sensing, nonlinear optics, and filters. Herein, we experimentally demonstrate an active terahertz (THz) quasi-BIC device induced by the polarization conversion in a liquid crystal (LC)-integrated metasurface, which consists of a symmetrically broken double-gap split ring resonator (DSRR), an LC layer, and double graphite electrodes. In the process of LC orientation control under the external field, the device realizes the active control from the OFF state to the ON state. In the OFF state, the LC has no polarization conversion effect, and the device behaves in a non-resonant state; but for the ON state, the device exhibits obvious quasi-BIC resonance. Furthermore, we achieve asymmetric transmission based on polarization-induced quasi-BIC modulation precisely at the quasi-BIC resonance position, and its isolation can be controlled by the external field. The study on dynamic quasi-BIC by the LC-integrated metasurface introduces a very promising route for active THz devices, which guarantees potential applications for THz communications, switching, and sensing systems.

Circular Microstrip Antennas in 5G: Evaluating Metamaterial Integration

The rapid emergence of Fifth-Generation (5G) technologies necessitate the development of highly efficient antenna systems with compact design that can support Ultra-Wideband (UWB) frequencies. This work presents the design and enhancement of a Circular Microstrip Antenna (CMSA) for 5G UWB applications using metamaterials. The study focuses on the design of CMSA and the integration of a Complementary Split-Ring Resonator (CSRR) into the circular patch of the CMSA. The design is simulated using Computer Simulation Technology (CST) Studio 2023. The system design without metamaterials achieved a gain of 5.28 dBi and a bandwidth of 353.0 MHz. The integration of the CSRR led to an improvement in gain, 5.39 dBi at 3.8 GHz, which is above most of the literature reviewed, although there was a slight reduction in bandwidth to 135.2 MHz. The objectives of achieving a CMSA design with a gain between 5 to 10 dBi while maintaining a compact size were accomplished. Despite the slight reduction in bandwidth observed when integrating the CSRR into the CMSA, the overall results highlight the significant role metamaterials played in enhancing the performance of microstrip antennas for 5G technology applications.