Square-ring Resonator Research Articles

UWB bandpass filter with tilted square shape ring topology sandwiched in the middle of interdigital structure

ABSTRACT This paper consists of compact novel design and high-performance ultra-wide band (UWB) bandpass filter (BPF) employed with square ring resonator (SRR) sandwiched between an interdigital structure (IDS). The unique combination of these microstrip resonators achieves a good selectivity across the passband with good rejection performance. The proposed structure also achieves less complexity and ease of fabrication. The passband extends from 4.2 GHz to 10.9 GHz with a notch band of 3 dB fractional bandwidth 88% centred at 7.6 GHz. The first passband in UWB BPF has minimum insertion loss as 0.59 dB and maximum return loss as 40.1 dB, whereas second passband has minimum insertion loss as 1.33 dB and maximum return loss as 36.62 dB. The presented filter structure is designed using Keysight Advance Design System (ADS). The simulated s-parameter characteristics performance is found to be in good agreement with the measured result.

A high Q-factor metamaterial sensor based on electromagnetically induced transparency-like

This paper proposes an electromagnetically induced transparency-like (EIT-like) metamaterial with a high-quality factor (143.54), which is composed of a square ring resonator (SRR) and a cross-shaped resonator (CR). The designed metamaterial generates a sharp transparency peak at 15.79 GHz. The electric field distributions reveal that appearance of the transparency window results from the coupling between bright mode and dark mode. Moreover, analysis of the surface current distributions verifies that the EIT-like effect is induced by the destructive interference of the electric dipoles . Furthermore, the metamaterial is equated to a circuit model, which provides a better fit to the simulated transmission spectrum. These theories fully explain the generation mechanism of the EIT-like phenomenon. In addition, the EIT-like metamaterial is able to detect the dielectric constant of the target analyte (glucose solution), and the sensing performance is evaluated. The results demonstrate that the sensitivity (S) is 4.80 GHz R−1IU−1 and the figure of merit (FOM) reaches 43.71. The proposed EIT-like metamaterial shows prominent sensing abilities, consequently it has potential applications in environmental monitoring, biological and chemical measurements.

Chipless RFID Tag Implementation and Machine-Learning Workflow for Robust Identification

In this work, we describe a complete step-by-step workflow to apply machine-learning (ML) classification for chipless radio-frequency identification (RFID) tag identification, covering: 1) the tag implementation criteria for circular ring resonator (CRR) and square ring resonator (SRR) arrays for ML interoperability; 2) the data collection procedure to get a sufficiently representative dataset of real measurements; 3) the ML techniques to visualize the data and reduce its dimensionality; 4) the evaluation of the ML classifier to ensure high-accuracy predictions on new measurements; and 5) a thresholding scheme to increase the certainty of the predictions. The differences in the tags’ frequency responses are maximized by optimizing the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Hamming distance</i> between the tag identifiers (IDs) and by controlling each resonator array’s radar cross section (RCS) level. We show that the proposed workflow achieves perfect accuracy for the identification of four tags at a fixed distance of 160 cm. We also evaluate the performance of the proposed workflow to identify up to 16 tags within a flexible range (up to 140 cm), showcasing the tradeoff between the number of tags that can be correctly classified based on the reading range.

A new tunable bandstop filter square-ring resonator using varactor diodes.

This work presents the development of a bandstop filter with a tunable response. Varactor diodes are used as control elements. Studies and investigations demonstrate the influence of the variable capacitance on the input admittance and on the S-parameters frequency responses of the proposed square-ring resonator geometry. The design of the square-ring resonator is based on mathematical modeling of ideal transmission lines, considering parameters of characteristic admittance and electrical length for odd and even excitation modes. Based on S-parameters in ports, an equivalent circuit model of the resonator geometry is presented. The corresponding results are compared with numerical simulations. Comparative analyses are presented in order to guide the process of optimizing the physical dimensions of the layout. A prototype with dimension 0.0272 [Formula: see text] was designed, fabricated, and tested. As a measured result, a filter with two rejection bands was obtained, the first at 0.6-1.15 GHz and the second at 1.71-2.28 GHz, with 63.0 and 29.0% tuning range, respectively. In comparison with bandstop filters from the literature, the proposed reconfigurable filter presents a larger tuning range for the first band, sufficient inband rejection levels for several applications, and reduced physical dimensions. The proposed configuration is an attractive reconfigurable filtering device for use in modern communication systems operating below 3.0 GHz.

Analysis and characterization of structural, dielectric and magnetic properties of MgxCo(0.90−x)Zn0.10Fe2O4 nanoparticles based flexible metamaterial absorber for wireless communication

The anisotropic flexible metamaterial absorber (FMA) structure comprises a resonating layer, a ferrite-based flexible substrate layer, and a back layer. The sol-gel method is used to prepare the ferrite-based nanomaterial for enhancing absorbability. The solution prepared material is according to the formula of MgxCo(0.90−x)Zn0.10Fe2O4 and specified as X25, X50, X75 for X = 25%, 50%, and 75%, respectively. Then the proposed ferrites materials are characterized by XRD, and FESEM, respectively. Moreover, the magnetic and dielectric properties of the proposed MgxCo(0.90−x)Zn0.10Fe2O4 ferrites samples were explored for microwave applications. The dielectric constants and loss tangents of the fabricated, flexible substrates are measured at a frequency range of 3–7 GHz using the DAK 3.5. The computed relative permittivity values are 2.95 for X25, 3.55 for X50, and 4.05 for X75, respectively, while the loss tangents values are 0.00295 for X25, 0.00495 for X50, and 0.00695 for X75. Whereas the permeability and magnetic loss tangent values varied from 0.875 to 1.00 and 0.00225–0.00585, respectively. Finally, the resonators of the absorber consist of a Y-style shape, square-shaped metallic plate resonator, square ring resonator (SRR), and cross-liked shape. The proposed flexible metamaterial absorber (FMA) structure is developed on MgxCo(0.90−x)Zn0.10Fe2O4 nanomaterial-based flexible substrate with dimensions of 0.110λ x 0.110λ x 0.017λ to validate the design experimentally. The electrical dimension is calculated at a 5.5 GHz resonance frequency. The simulated results from the CST Microwave Studio simulator reveal that absorption peaks at 5.5 GHz with a 99.99% absorption that includes the C band frequency that can be used in satellite applications. The proposed FMA structure achieved a 60° incident angle response for TE and TM modes. The structure has superiority with compact dimensions, lightweight, and flexibility and can be used for C band wireless communications.

Millimeter-Wave Broadband MIMO Antenna Using Metasurfaces for 5G Cellular Networks

Developing a millimeter-wave (mm-wave) antenna that enables wide bandwidth with its operating band covering the entire global 5G spectrum is highly desirable but very challenging for achieving both compact size and high-performance antenna. Herein, the mm-wave microstrip patch antenna (MPA) and its multiple-input multiple-output (MIMO) configuration based on the metasurfaces for 5G system applications are proposed and investigated by the simulation method. To improve performance and keep the low-profile and low-cost MPA antenna, square ring resonator (SQRR) metasurface and radiating patch are printed on a single dielectric layer. With the presence of the metasurfaces that acting as a secondary radiator, the performance of the designed antenna is significantly improved with a wide operating band in the range of 23.9-30.7 GHz, high peak gain of 9.4 dBic, and radiation efficiency of above 87%. Based on this design, four-port MIMO antenna configuration is performed for evaluating a MIMO system that realizes the advantage features such as compact size, wide bandwidth covering the entire global mm-wave 5G spectrum band of 24.25-29.5 GHz, and excellent diversity performance characterized by good isolation between the adjacent elements and low envelope correlation coefficient. Thus, the MIMO antenna design is a very promising candidate for 5G MIMO mm-wave applications, specifically in cellular systems.

Compact MIMO Microstrip Antenna for Wireless PAN

This article presents compact wideband four elements Many-Input Many-Output (MIMO) antenna using Defect Ground Structure (DGS). The proposed structure is dedicated to cover 4G-LTE/Sub 6 GHz bands in the 2.5/3.5/5.5 GHz frequency range and WLAN, Wi-Fi, and (LTE bands 41, 42, 43, 46, and 48). It also includes new radio (NR) technology which has different bands for 5G and (sub-6 GHz bands 47, 48). The designed antenna is very compact in size having dimensions of 28 mm x 29.58 mm x 0.8 mm. Isolation is achieved with square ring resonators (SRR). Isolation is further enhanced by inserting slots and SRRs between antennas. MIMO antenna characteristics such as high isolation (45 dB), low envelope correlation coefficient (0.01), and high diversity gain (10 dB) are measured. Furthermore, a wide impedance bandwidth of 8 GHz is measured. MIMO antenna is verified with a Software-Defined Radio (SDR) platform.

Metamaterial solar absorber based on titanium resonators for operation in the ultraviolet to near-infrared region

In this work, we design an ultra-broadband metamaterial solar absorber with near-unity absorption. The absorber’s structure is optimized by using the particle swarm optimization algorithm. A unit cell of the absorber consists of three T i / T i O 2 / T i square disks enclosed by a Ti square ring resonator, all superimposed on a thin stack of T i O 2 / T i films. The optimized structure shows high average absorption of 96.92% over the full wavelength range of 200–3200 nm. The over 90% absorption bandwidth is 3000 nm, which covers the ultraviolet, visible, and near-infrared regions. The solar absorption of the structure is 95.5% in the range of 280–3200 nm. The absorber is polarization independent and insensitive to incident angle changes. The absorption remains higher than 80% and 75% for TM and TE polarizations, respectively, even under oblique incidence radiation up to 55°. The structure possesses high thermal and chemical stability owing to the use of Ti and T i O 2 materials. Due to its outstanding features, the absorber has high potential to be used in solar energy harvesting, thermo-photovoltaics, and thermal emitting applications.

Cascaded plasmon-induced transparency in spoof surface plasmon polariton waveguide

Manipulating spoof surface plasmon polaritons (SPPs) effectively has promising applications in developing ultracompact plasmonic circuits. Research on versatile components in planar spoof SPP waveguides has attracted widespread attention over the decades. In particular, cascaded chip-scale devices play an important role in enhancive buffering, highly-sensitive sensing and nonlinear interaction. Herein, we propose a novel strategy to manipulate the switching and slow wave features of spoof SPPs on the basis of plasmon-induced transparency (PIT) spectral responses. A combined module consisting of split square-ring resonators and electric-LC resonators is loaded with a spoof SPP waveguide along the propagating trajectory, where the destructive interference between the two resonators contributes to the PIT behavior and the group delay of the spoof SPPs. A modulation contrast of up to 16.2 dB is achieved for the spoof SPP transmission at the PIT peak frequency. The measurements are consistent with both full-wave simulations and theoretical calculations. Cascaded capabilities performed by installing multiple PIT modules at an interval of an equivalent wavelength are accomplished in the planar spoof SPP waveguide. The proposed strategy opens up fascinating prospects on highly integrated plasmonic circuits and networks.

Tunable balanced bandpass filter with wide frequency‐tuning range and high selectivity

AbstractA tunable balanced bandpass filter (BPF) with a wide frequency‐tuning range (FTR) and high selectivity is presented. The designed BPF is implemented by utilizing varactor‐tuned square ring resonators (SRRs) with parallel‐coupled feedlines. A wide FTR with an almost constant absolute bandwidth (CABW) can be realized by varactors Cv2 connected between SRRs. Four transmission zeros (TZs) can be obtained by the mixed electric and magnetic coupling, source‐load (S‐L) frequency‐variant coupling, and four shunt quarter‐wavelength open and short stubs. Meanwhile, two TZs on both sides of the passband keep the relative position unchanged to achieve high selectivity. The other two are generated to improve the out‐band rejection. In addition, by employing additional stubs and capacitances on the symmetry plane, the common‐mode (CM) suppression can be enhanced. For verification, a tunable balanced BPF with 0.62‐1.27 GHz and four TZs was designed, manufactured, and tested. And experimental results agree well with the simulated ones.

Terahertz analysis of a highly sensitive MIM-SRR-TiO2 nanostructure for bio-sensor applications with the FDTD method

This work analyzes the transmission line characteristics of a plasmonic metal-insulator-metal (MIM) waveguide and a square ring resonator (SRR) for dual band applications. The MIM-SRR-based bio-sensor using 3-Aminopropyl triethoxy silane (APTES) and titanium dioxide ( T i O 2 ) as a precursor material are proposed and investigated in this paper. The MIM waveguide characteristics such as propagation length and effective refractive index have been obtained using the finite differential time domain (FDTD) solver of CST studio suite. The MIM-based SRR band-pass filter was designed and analyzed at 1300 nm (230.6 THz) and 1600 nm (187.37 THz) wavelengths. In this work, the bio-compatibility material T i O 2 is used as an agent of bio-molecules detection, and APTES is used as a linker between silicon dioxide and T i O 2 . The proposed MIM-SRR- T i O 2 -based bio-sensor is operated at 1320 nm (227.115 THz) and 1630 nm (183.922 THz). The proposed MIM-SRR-APTES- T i O 2 bio-sensor is operating at dual pass bands of 1415 nm (211.867 THz) and 1762 nm (170.143 THz). The proposed MIM-SRR-APTES- T i O 2 has a Q -factor of 22.353 and 20.655 and a sensitivity of 571.02 and 877.86 nm/RIU at 1415 and 1762 nm, respectively. APTES and T i O 2 are responsible for detecting cervical cancer, which is generally observed in woman. The scalability and multiplexing capability of semiconductor-based technology, silicon photonic ring resonators, are promising analytical tools for detecting various sensing applications. The overall size of the proposed bio-sensor is 1200 n m × 300 n m × 60 n m .

Alternative material titanium nitride based refractive index sensor embedded with defects: An emerging solution in sensing arena

This article presents an ultra-compact refractive index sensor based on titanium nitride (TiN), a well-known alternative plasmonic material. The designed sensor consists of a straight waveguide, coupled with a groove and a Square-Ring Resonator (SRR). In addition, nanosized TiN dots are embedded in the waveguide and groove to enhance sensing performance. The spectral characteristics of the proposed sensor are numerically analyzed using the Finite Element Method (FEM). After extensive simulations, the most optimal structure provides a maximum sensitivity of 1074.88 nm/RIU and a Figure of Merit (FOM) of 32.4 and proves to be tolerant against probable real-life manufacturing defects. Furthermore, the incorporation of TiN equips the illustrated sensor with numerous advantages, for example, immunity to oxidation, optical tunability, capability to endure high-temperature, and compatibility with the standard Complementary Metal Oxide Semiconductor (CMOS) fabrication process. The major pitfall of traditional plasmonic metals is that the metals lack all these qualities, limiting real-life implementations of plasmonic devices. Therefore, the proposed model is superior to the conventional Metal–Insulator–Metal (MIM) setup and is expected to facilitate the development of practical, robust sensors.

An Ultra-Wideband Band Pass Filter using Metal Insulator Metal Waveguide for Nanoscale Applications

A T-stub Square Ring Resonator (SRR) based Ultra-Wide Band (UWB) Band Pass Filter (BPF) is studied and investigated in this paper. The proposed filter is based on coupled feed line connected to the T-stub SRR. Ultra-wideband characteristics can be realized by adjusting the T-stub lengths and coupling the gaps between both sides of waveguides and SRR. The characteristics of the T-stub SRR show that the miniaturized UWB BPF can be operated at THz frequencies. The proposed UWB filter is simulated and analyzed using the Finite Differential Time Domain (FDTD) solver-based Computer Simulation Technology (CST) studio suite. The resonance conditions are explained and the transmission performance of the filter agrees with the simulated and theoretical calculations. The proposed filter is best suitable for Electronic-Plasmonic Integrated Circuits (EPICs).

Concurrent Dual and Triple Band Square Ring Resonator Base-Band Filter using Metal-Insulator-Metal for Plasmonic Applications

Ring resonators are capable of providing high-quality factors with low insertion loss, which are the factors for considering it as a potential technique of guiding signal in the nanometer wavelengths. In this paper, a Nanoplasmonic configuration of a resonator comprising of the square ring known as Square Ring Resonator (SRR) is designed and analyzed for multiple band characteristics. The performance analysis of two different structures of the square ring resonators are presented in terms of the simulation reports like reflection and transmission coefficients, and field distribution plots. The designed Band Pass Filter (BPF) expressed excellent performance in the optical bands and hence are best suitable for Photonic Integrated Circuit (PIC) applications.

Design of Metal Insulator Metal based Square Ring Resonator Plasmonic Filter using Silica Slits for Dual Band Applications

In this paper, Metal-Insulator-Metal (MIM) based dual-band plasmonic bandpass filters (BPF) with single and dual silica slits design and analysis is presented. The Square Ring Resonator (SRR) is coupled using Coupled feed line for dual-band operations. The coupled feed line is used for dual-band operating wavelengths, 1300 nm (230.6 THz) and 1600 nm (187.37 THz). Design and simulations are performed using complex electromagnetic simulatorknown as computer simulation technology (CST) microwave tool. The proposed filters are used for plasmonic single and dual-band bandpass filter (BPF) applications in photonic integrated circuits (PIC’s).

Research on coupling property of side-coupled asymmetric square-ring resonator in a plasmonic waveguide

The characteristics of resonant modes in the side-coupled asymmetric square-ring resonator based on a plasmonic waveguide are investigated. The 1-order modes and 2-order modes can be manipulated by adjusting the longitudinal distance Δz and transversal distance Δx of the metal block in the square air cavity. The coupling and splitting effect of the resonant modes in the asymmetric square ring resonator are exploring. The proposed structure is potential in sensing and filtering.

Direct Coupling Strategy in Plasmonic Nanocircuits for Low Loss and Easy Fabrication

Plasmonic nanocircuits can deliver light in subwavelength scale, however, require state-of-the-art fabrication process due to the ultra-small footprints. Here, we introduce direct coupling strategy based on metal-insulator-metal (MIM) waveguide systems to reduce the system loss as well as the fabrication difficulty and increase the structural stability. Following this strategy, the coupling between the input waveguide and square ring resonator (SRR) can be realized via an aperture, and for the coupling between SRRs, the metal gap can be removed. The numerical results show that such direct coupling can produce similar effects with conventional indirect coupling in MIM waveguide systems, and the physics mechanism behind as well as influences of geometric parameters on transmission spectrum is also investigated. This work provides a simpler approach to realize on-chip plasmonic nanodevices, such as filters, sensors, and optical delay lines, in practice.

Square‐ring metamaterial for radiation characteristics enhancement of an SIW cavity‐backed slot antenna

Design and analysis of a low-impedance metamaterial (MTM) along with its application to antenna design are presented in this manuscript. This low-impedance MTM is a square-ring (SR) resonator, which exhibits low-impedance property irrespective of the polarization and incident angle of the imposed EM wave. This SR MTM slab is placed directly atop an SIW cavity-backed slot antenna for gain enhancement, eliminating the air gap between them. The peak realized gain improvement in the broadside direction is 8.3 dB, whereas the overall thickness of the antenna is 0.103 λ0 at the operating frequency of 9.78 GHz. Moreover, the front-to-back ratio is 26.5 dB and the cross-polarization is negligibly altered by this gain enhancement method. This concept is experimentally verified with fabrication and measurements.

Plasmon-induced anti-transparency modes in metasurface

We investigate plasmon-induced anti-transparency (PIAT) modes with a metallic metasurface on a dielectric substrate through the finite-element method. Multiple spectral splits are achieved by breaking the symmetry of square-ring resonators. The asymmetry of the structure is attained by incorporating cuts in the rings and increasing displacement of cuts in opposite directions. The high asymmetry decreases the spectral width and enhances the intensity of PIAT resonances. A unified mechanism for generating the PIAT resonances and plasmon-induced transparency (PIT) resonances is studied and agrees with the simulation results. These resonances are highly sensitive to the type of background materials and can be used for detecting cancerous and healthy tissues. A high figure-of-merit (FoM) of 808 is calculated for biosensing. The multiple high-quality factor resonances can also be used for optical filters (band-stop filtering for PIAT modes and band-pass filtering for PIT modes), slow light devices, and switching.

Metal-insulator-metal nano square ring resonator for gas sensing applications

ABSTRACT In this paper, three designs of Square Ring resonator (SRR) based on metal-insulator-metal (MIM) WG are reported. The transmission spectra and electric field distribution of the sensor structure are simulated using finite element method (FEM). The effect of structural parameters on the spectral characteristics and sensing performance are investigated comprehensively. The maximum achieved sensitivity and figure of merit of the sensor reached 1320 nm/RIU and 16.7, respectively. Due to the high performance and easy fabrication, this kind of plasmonic structures can find noteworthy applications in integrated optical circuits and on-chip nano-sensors.