Split-ring Resonator Unit Cells Research Articles

Novel metamaterial array-based dual port MIMO antenna using low profile substrate with feature multiband, and high isolation for sub-6G, IoT, and WiMAX applications

This article represents a single-layered two-port MIMO antenna loaded into a compact plane-patterned metamaterial (MTM) structure for a 5G communication system. The antenna operates at three bands to investigate metamaterial properties in addition to diversity parameters, an arrangement of a series of arrays suggested a 2-port design antenna and a circular-shaped split ring resonator unit cell was developed. The design of a single port antenna utilizes 1 × 3 MTM unit cells for each component. This antenna operates within a frequency range ranging from 1 GHz to 15 GHz. Additionally, the suggested MIMO antenna offers a dominant isolation of –55dB. The measurement’s results show that, with an entire antenna size of 112 mm × 26.5 mm and a 3.33 GHz bandwidth, the MIMO antenna is achieved with good efficiency and CCL < 0.35, considerable DG > 9.97dB, ECC < 0.18, and TARC <–9.97. The presented design is suitable for medical imaging, RFID, Bluetooth, Wi-Fi, WiMAX, IOT, satellite communication systems, and the 5G and sub-6 GHz spectrum.

Design and analysis of ultra-wideband microstrip patch antenna with various conductive materials for terahertz gap

The paper explores the design and analysis of a wideband microstrip patch antenna with a metallic patch and a 3 × 3 split ring resonator (SRR) array operating in the 0.1–5 THz frequency range. The antenna's structure incorporates different conductive materials such as gold, silver, and graphene as a metallic patch. The dimensions of the metallic patch and SRR are calculated to achieve wideband operation within the desired THz range. The SRR array enhances electromagnetic resonance, thereby improving bandwidth and radiation characteristics for medical imaging. The study discusses the equivalent circuit and design equations for the microstrip patch antenna and SRR unit cell. For designing and analyzing the proposed antenna, CST Microwave Studio 2019 software have been used. Performance parameters such as return loss, bandwidth, gain, efficiency, directivity, VSWR, and radiation pattern have been evaluated. The advantages and limitations of each conductive material are evaluated to determine their suitability for THz-based medical imaging applications. The goal is to maximize the antenna's bandwidth, gain, and image resolution for medical imaging purposes. The findings highlight the performance characteristics of gold, silver, and graphene as conductive materials for medical imaging applications, facilitating the development of high-resolution, non-invasive imaging systems with improved diagnostic capabilities.

High specificity THz metamaterial-based biosensor for label-free transcription factor detection in melanoma diagnostics

In this work, we present a promising diagnostic tool for melanoma diagnosis. With the proposed terahertz biosensor, it was possible to selectively and sensitively detect the early growth response protein 2, a transcription factor with an increased activity in melanoma cells, from a complex sample of cellular proteins. Fundamentally, the sensor belongs to the frequency selective surface type metamaterials and consists of a two-dimensional array of asymmetrically, doubly split ring resonator unit cells. The single elements are slits in a metallic layer and are complemented by an undercut etch. This allows a selective functionalization of the active area of the sensor and increases the sensitivity towards the target analyte. Hereby, specific detection of a defined transcription factor is feasible.

A Study of Dielectric Effects on Resonance Frequency of a Spit Ring Shaped Inclusion

Resonator designs are central to the development of subwavelength unit structures of metasurfaces to create exotic and unique electromagnetic properties by modifying the host structure to tune impinging electromagnetic waves. The act of intentional control of propagating electromagnetic fields are actively being explored in wireless radio environment control for sixth generation (6G) and beyond. In this paper, we study the effect of dielectric properties on electric field distribution and resonance frequency of a circular split ring resonator (SRR). The subwavelength resonator structure is modelled and simulated using High Frequency Structure Simulation (HFSS) software. Rogers RO3003 and RO3210 were used at different thickness to study the field distribution and its effect on resonance frequency of the SSR. The results show a decrease in resonance frequency of 38.41% from RO3002 (lower relative permeability of 3) to RO3210 (higher relative permeability of 10.2). With change in Rogers RO3210 thickness from 1mm to 1.525mm, the resonance frequency has changed from 5.5GHz to 5.2313 GHz. This indicates that the material composition of the substrate and the physical dimension of the SRR unit cell affects the resonance frequency of the structure.&nbsp;&nbsp;&nbsp;&nbsp

Improved performance for antenna based on a combination of fractal geometry with CSRR

ABSTRACT In this paper, an antenna design method operating at 3.5 GHz for 5G system is presented to improve its performance. The antenna is designed using fractal geometry combined with an imperfectly structured ground plane. In which, the radiation surface has the form of a Minkowski island fractal geometry, and the removed part of the ground is a complementary split ring resonator unit cell. In this design, the substrate material is FR4-epoxy microwave laminates with dielectric constant ϵ = 4.4, loss tangent (tan δ) of 0.02, and h = 1.6 mm thickness used to design the antennas. HFSS software is used in the simulation with the feeding method with a microstrip line. The proposed antenna has a significant performance increase compared to the original microstrip antenna such as reduced about 56% reduction in total size, enhanced 207% bandwidth, increased peak gain to 4.66 dB, and improved radiated efficiency to 89.3%. The physical model of the antenna has been fabricated and measured to verify the correctness of the design.

Gain Enhancement of Patch Antenna Using High Refractive Index Metamaterial-based Bi-convex Lens for Base Station Applications

ABSTRACT In this paper, a high refractive index-based metamaterial Bi-convex lens superstrate for the gain enhancement of broadside radiating antennas like microstrip antennas is presented. Fundamentally, an effective HRI medium is created by the Single Ring Split Ring Resonator unit cells printed on an FR-4. By stacking the multiple layers of the superstrate, a virtual HRI-based equivalent Bi-convex lens is constructed to focus the incoming diverged beam from a patch antenna. A gain enhancement of 4.42 dB is achieved with the help of a 3-layer HRI-based Lens superstrate. The simulation and measurement results are also almost agreed on the same.

Electrothermally controllable terahertz metamaterial for sensing application

A design of electrothermally controllable terahertz (THz) metamaterial (ECTM) is presented, which is composed of split-ring resonator (SRR) on Si substrate. All SRR unit cells are connected to form ECTM with a current loop. By driving a direct-current (DC) bias voltage on ECTM, the heating energy is generated and then changed the surrounding refraction index. Therefore, it results in a resonant shift. While the DC bias voltage is applied from 0 volt to 0.95 volts in transverse electric (TE) mode, ECTM shows a tunable triple-resonance with the tuning ranges of 24 GHz, 40 GHz, and 32 GHz, respectively. The maximum sensitivity is 42 GHz/volt. Meanwhile, the maximum Q-factor is 24.5. These results pave a way for ECTM to be applied in polarization-dependent filters and sensors for further tunable and controllable optoelectronics applications.

A Multiband, Polarization-Controlled Metasurface Absorber for Electromagnetic Energy Harvesting and Wireless Power Transfer

A multiband, polarization-controlled energy harvesting metasurface is presented in this article for harvesting electromagnetic energy in the Wi-Fi bands. Inspired by the split-ring resonator (SRR), a metasurface of SRRs is designed by nesting multiple SRRs together. The novelty of the design lies in the controllable multiband polarization and adjustable absorption frequency, so as to achieve the active modulation of energy harvesting on the metasurface at different frequencies. The metasurface is composed of a periodic array of SRRs unit cells, an impedance-matched rectifier, and a load. Metasurface arrays and rectifier integration are proposed to reduce power losses, while the channels formed by the array enhance energy density and improve the ability to capture energy. Moreover, the design for the rectifier is capable of rectifying RF energy from multiple Wi-Fi bands simultaneously at low input RF power density. The finite array of <inline-formula> <tex-math notation="LaTeX">$5\times $ </tex-math></inline-formula> 5 SRRs absorber is fabricated and tested. Measurements in an anechoic chamber show that the fabricated prototype reaches the efficiency of 66.5&#x0025; at 2.4 GHz, 40.6&#x0025; at 5.2 GHz, 35.6&#x0025; at 5.8 GHz under transverse electric (TE) polarization, and 38.3&#x0025; at 5.3 GHz under transverse magnetic (TM) polarization when the incident power density is greater than 66 <inline-formula> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula>/cm².

Multilayered metamaterials array antenna based on artificial magnetic conductor's structure for the application diagnostic breast cancer detection with microwave imaging

In this work, a small multilayer ultra-wideband (UWB) patch antenna for microwave breast imaging (MWI) applications was developed both theoretically and experimentally. However, to improve the antenna performance relating to the bandwidth (BW), the radiating element of the suggested initial antenna is modified by adding a modified split ring resonator (SRR) and slits in the patch as well as the ground plane. Then, to achieve the requisite antenna properties for MWI applications such as the gain and directivity, the antenna is equipped with a uniplanar artificial magnetic conductor (AMC) structure made up of a 3 × 3 array of square modified SRR unit cells. The final proposed prototype has a relatively small size of 20 × 19 × 1.6 mm3 and it accomplishes a return loss below -10 dB (S11< -10 dB) at overall BW of 7 GHz (4.1 – 9.7 GHz) with more than 5 dBi realized gain. In this way, the characteristics of the fabricated antenna are measured to examine the antenna performance. Indeed, the fidelity factor of face-to-face (FtF) and side-by-side (SbS) scenarios are also noticed for the same frequency range. In the final analysis, a simulation model of the antennas, which operate as a transceiver, and a breast phantom model with tumor sample are proposed for detecting cancerous tumor cells within the breast.Hence, the proposed design is suitable in the biomedical applications such as tumor cell detection.

Design of highly directive slot antenna using metamaterial structure under optimal condition

In this article, a highly directive slot antenna design using a parallel incident magnetic metamaterial (MTM) structure has been presented. A split ring resonator (SRR) structure having mu near-zero and epsilon very large with low impedance behavior is employed to enhance the directivity of the antenna. In the proposed optimized design, four-MTM slabs with an array of 2 × 2 SRR unit cell have been placed perpendicularly over the slot antenna to enhance the directivity. The thickness of utilized MTM slab in the vertical direction is under the optimal condition, which is highly desired to obtain better improvement in directivity. In spite of directivity enhancement of about 6 dB, antenna miniaturization of 11.4% is also obtained due to the loading effect of the MTM slab. The proposed directivity enhancement approach of the slot antenna is established by simulation and verified by measurements. It is perceived from both measured and simulated results that over the whole working band, a significant directivity enhancement is sustained along with reduced backward radiation compared to the unloaded slot.

Oblique and Polarization Independent Metasurface-Based Absorber for Bio-Sensing Applications

In this paper, a submillimetric/THz metasurface polarization/oblique independent absorber is designed and characterized. The absorber is designed using a periodic arrangement of a modified split ring resonator unit cell. The symmetric absorber is insensitive to the variation of incident angles and polarization angles. The results confirm that perfect absorption is achieved (close to 100%) for either TM or TE polarization at 300 GHz. Moreover, the absorber is efficient for normal and oblique incident angle (above 90% for 45° angle of incidence). In all the presented cases, the full width half maximum bandwidth is 20 GHz. The absorber unit cell size is only 0.0052 λ 0 × 0.0052 λ 0 and it has a low-profile thickness = 0.0002 λ 0, at the operating frequency. Also, an absorber-based biosensor is presented. The sensing has proved the coating analyte thickness can be detected by shifting the absorption frequency. The maximum sensitivity is 24.9% RIU−1 with a low-profile maximum of 50 µm thickness. Analytical formulas for the frequency shift have been extracted. The presented results are discussed based on 3D full-wave EM simulations.

Simulated Triple Circular Split-Ring Resonator Metamaterial Unit Cell for THz application

Metamaterial used widely nowadays to overcome the limitation of the natural material in manipulating the electromagnetic wave and radiation. Split-Ring Resonator (SRR) have been used widely as a design to manipulate the electromagnetic waves but none of them used for higher frequency such as light frequency. Therefore, the objective of this paper is to design SRR unit cell that is capable to bend the light wave. The negative value of material properties obtained from the simulation of the metamaterial at three different part which are at phase=0, real value and imaginary value. CST Microwave Studio 2018 used as a simulation software. The results show all the negative value of material properties obtained at different frequency range. However, the negative value of material properties at phase=0 and imaginary part is obtained at same frequency range. While for real part, the negative value for all material properties occurred at different frequency range. This SRR design is suitable to manipulate the lights radiation waves.

Design and Analysis of $D$ -Band On-Chip Modulator and Signal Source Based on Split-Ring Resonator

In an effort toward high-speed and low-power I/O data link in the future exascale data server, this paper presents a signal source and a modulator in the $D$ -band. The split-ring resonator (SRR) structures are used to boost both the signal power and the extinction ratio (ER). The modulator manifests itself as a compact SRR whose magnetic resonance frequency can be modulated by high-speed data. Such a magnetic metamaterial achieves a significant reduction of radiation loss with high ER by stacking two auxiliary SRR unit cells with interleaved placement. The high-Q tank for oscillation is realized by a stacked SRR decorated with slow-wave transmission line (T-line) for electric field confinement. A four-way power-combined fundamental 80-GHz coupled-oscillator network is magnetically synchronized by the slow-wave T-line, which is frequency doubled to 160 GHz. Fabricated in the 65-nm CMOS process, the measured results show that: 1) the modulator achieves 3-dB insertion loss at the on-state with 43-dB isolation at the off-state, leading to a 40-dB ER at 125 GHz within an area of only $40\,\,\mu \text {m} \times 67\,\,\mu \text{m}$ and 2) the signal source achieves 6.3% frequency tuning range (FTR) with 3.7-mW peak output power at 160 GHz within 0.053-mm2 active area. It has a measured phase noise of −105 dBc/Hz at 10-MHz offset, 5.5% dc-to-RF power efficiency, 70.1-mW/mm2 power density, FOM of −171 dBc/Hz, and FOM $_{T}$ of −172.7 dBc/Hz.

Metamaterial superstrate microstrip patch antenna for 5G wireless communication based on the theory of characteristic modes

Abstract Metamaterials (MTMs) have received considerable attention due to their novel electromagnetic properties. Their applications include enhancing gain and bandwidth in microstrip antennas. In this article, a dual band microstrip antenna design based on characteristic mode analysis (CMA) using MTM superstrate is proposed for 5G wireless communication. The CMA is used for the modelling, analysis and optimization of the proposed antenna to examine the underlying modal behaviour of the MTM unit cell and to guide mode excitation. The antenna structure consists of a microstrip feed line connected to a rectangular patch. Then triangular split ring resonator unit cell is inserted on the ground of a traditional patch antenna that resonates at 15 GHz to produce additional resonance at 10 GHz. A planar array of 2 × 3 triangle MTM unit cells is used as superstrate to improve the gain and bandwidth at both resonances simultaneously. The optimal distance between MTM superstrate and the antenna patch is determined using the Fabry-Perot cavity theory to maximize power directivity and efficiency of the proposed antenna. The CST microwave studio software is used to model and optimize the proposed antenna. A prototype of the designed antenna that was fabricated showed good agreement between measurement and simulation results.

Microwave Imaging for Breast Tumor Detection Using Uniplanar AMC Based CPW-Fed Microstrip Antenna

A novel, low cost, and comprehensive microwave imaging (MWI) system is presented for the detection of unwanted tumorous cells into the human breast. A compact metamaterials (MTM) artificial magnetic conductor (AMC) surface-inspired coplanar waveguide fed (CPW-fed) microstrip antenna is developed for MWI applications. The initial wideband CPW antenna is designed by the modified oval shape patch and half cycle copper stripe line ground. The antenna is incorporated with two layers uniplanar AMC structure which is composed of a $5\times 5$ array of square modified split ring resonator unit cells to obtain the desired antenna characteristics for the MWI applications like breast imaging. The metamaterial-based AMC structure improves the gain about 5 dB and produces stronger directive radiation characteristics. The enhancement of CPW performance proofs the effectiveness of the double layer MTM-AMC structure and its suitability for MWI. A microcontroller-based PC controlled alternative mechanical imaging system is designed to collect the scattering signal from the CPW-fed antenna. The changes of reflection and transmission coefficient with the variation of dielectric content into the breast phantom structure are analyzed. The remarkable deviation of scattered field is processed by image processing program using Matlab. By using these AMC inspired CPW-fed antenna based microwave imaging, the system can clearly detect the tumor inside the breast phantom.

Efficient design of electrically small antenna using metamaterials for wireless applications

In this paper, a simple and efficient approach is presented for the design of a compact CPW fed slot antenna loaded with complementary split ring resonators (CSRRs) and metamaterial (MTM) slab. It has been shown that the fundamental resonant frequency of the conventional slot antenna can be lowered considerably by loading CSRRs and an MTM slab. The MTM slab consists of an array of 1 × 3 single-sided periodic structure of split ring resonator unit cells. The CSRRs are incorporated on both sides of the rectangular slot and the MTM slab is placed below the dielectric substrate of the antenna to achieve miniaturization. About 56.7% miniaturization is attained for the proposed CSRRs and MTM slab loaded antenna in comparison to the conventional antenna. It is also observed that the minimal effect on the co-polarization and cross-polarization is obtained in the case of proposed antenna. The overall antenna size is 0.23 λ0 × 0.23 λ0 × 0.009 λ0, where λ0 is the free space wavelength. In this proposed antenna a high radiation efficiency of about 84.2% is obtained. Owing to the high efficiency and compact size, the proposed antenna will find broad applications in the field of wireless communication.

Design of tunable microwave transmission lines using metamaterial cells

In this paper, frequency tunable transmission lines are designed using metasurface split ring resonator unit cell. We prove that the tuning principle in metasurface transmission lines is based on the variation of the resonance frequency of the permeability. The frequency-tuning arises by changing the values of two gaps in the inner and outer rings of unit cell (g1 and g2). The branches of a disconnected gaps type conductor of each unit cell can be joined by switches (PIN diodes, MEMs, etc.). According to switch states ON or OFF, the unit cell has four different commutable behaviors which are 00, 01, 11, and 10. The results show that the resonance frequency of our metasurface transmission line is strongly shifted by about 2.5 GHz between the cases (01) and (11).

Mutual Coupling Reduction in Dielectric Resonator Antennas Using Metasurface Shield for 60-GHz MIMO Systems

An effective technique for reducing the mutual coupling between two dielectric resonator antennas (DRAs) operating at 60-GHz bands is presented. This is achieved by incorporating a metasurface between the two DRAs, which are arranged in the H-plane. The metasurface comprises an array of unique split-ring resonator (SRR) cells that are integrated along the E-plane. The SRR configuration is designed to provide bandstop functionality within the antenna bandwidth. By loading the DRA with 1 × 7 array of SRR unit cells, a 28-dB reduction in the mutual coupling level is achieved without compromising the antenna performance. The measured isolation of the prototype antenna varies from -30 to -46.5 dB over 59.3-64.8 GHz. The corresponding reflection coefficient of the DRA is better than -10 dB over 56.6-64.8 GHz.

Gain Enhancement of Planar Antenna Enabled by Array of Split-Ring Resonators

This communication proposes a high-gain bow-tie antenna operating over the frequency band of 5.5–8 GHz. The proposed antenna is comprised of a microstrip-to-slot transition line connected to bow-tie radiators. Seven slabs of split-ring resonator (SRR) unit cells are integrated into the orthogonal plane of antenna substrate to enhance its gain. Each slab consists of $2 \times 7$ double-sided SRR unit cells. A prototype of the antenna is fabricated and measured. The results indicate that the reflection coefficient is better than −10 dB over the frequency band of 3.5–8 GHz. The measured antenna gain varies from 10.2 to 13.8 dBi over a frequency range of 5.65–7.8 GHz. The measured radiation efficiency corresponds to 90% at 7 GHz. The cross polarization is better than −30 dB in the $E$ -plane at 6.5 GHz.

Tunable Terahertz Filter and Modulator Based on Electrostatic MEMS Reconfigurable SRR Array

This paper demonstrates a tunable terahertz (THz) filter and a modulator based on an electrostatic micro electro mechanical systems (MEMS) reconfigurable split ring resonator (SRR) array. The device uses tunable metamaterial concept, in which an RF-MEMS (radio frequency-MEMS) capacitor is embedded in each SRR unit cell to tune the electromagnetic resonant frequency. By utilizing THz time domain spectroscopy (THz-TDS) measurement and through the voltage actuation, we have controlled the THz transmission of the metamaterial device, and thus demonstrated a tunable filter. Since the low loss material of fused quartz is used as the substrate, the device shows a high contrast ratio THz switch at a given frequency by controlling the capacitance of the RF-MEMS capacitor. The dynamic performance of the switch, i.e., the modulation ability, is also characterized by THz-TDS. The measurement results show up to 2 kHz of the modulation speed with the TDS operated. The device is developed by the surface micromachining process with three photolithography steps.