Modified Split Ring Resonator Research Articles

A four-port wideband filtering monopole MIMO array for sub-6 GHz 5G communications

AbstractThis communication presents the significance of a four-port 2×2 multiple input multiple output antenna operating in mid-band frequency for 5G handheld device application. A microstrip-fed reference truncated decagonal monopole antenna operating at 3.9 GHz and a modified split-ring resonator (SRR)-based low-pass filter that excites at a cut-off frequency of 6.5 GHz are designed. On introducing a stub line in the SRR structure, the proposed filter shows a good out-of-band rejection beyond 6.5 GHz. By integrating the filter into the reference monopole, a wideband filtering monopole with improved stopband performance is obtained. A four-port MIMO array is constructed by orthogonally positioning the antenna with a center-to-center separation of 0.25λ0. To improve isolation, a pair of inverted L-stubs of varying lengths is introduced. The closed loop formed by the interconnection of stubs enhances isolation within the frequency range of 3–3.5 GHz. The fabricated prototype fosters an impedance bandwidth of 66.67%, isolation >18.5 dB, an average suppression of 15 dB, an average peak gain >3.7 dB, envelope correlation coefficient < 0.015, Actual Diversity Gain (ADG) > 9.9 dB, Effective Diversity Gain (EDG) > 8.8 dB, and efficiency >88%. The proposed design is suitable for 5G sub-6 GHz applications such as n48, n77, n78, n79 bands, WiMAX, and LTE bands 42, 43, 46, 47, 48.

Fractal metasurface for THz applications with polarization and incidence angle insensitivity

A Fractal metasurface-based absorber is designed to obtain a wideband absorption in THz frequency band. The developed absorber has a broadband absorption over more than 600 GHz bandwidth, from 0.6 THz to 1.2 THz, with a minimum absorption percentage of 70% and total absorption from 1 to 1.1 THz. The proposed fractal structure is investigated using a Modified Split Ring Resonator (MSRR). The absorption coefficient of the proposed fractal metasurface is compared with the modified initially SRR metasurface. The results indicate that by using fractal design, the metasurface operating band is summed up, resulting in a wide bandwidth. The absorption coefficient of the proposed fractal metasurface is studied using two different simulation software programs to ensure the obtained results, with a high agreement between the results of them. The designed metasurface has a similar absorption response for the different polarization of the incident wave. The impedance of the designed metasurface indicates that, for the operating band, the fractal metasurface has a surface impedance of around 377 Ω, indicating a good matching between the designed metasurface and air. Different incidence and polarization angles are studied with results showing its insensitivity to both of them. The designed metasurface is compared with previously published works, showing wider bandwidth, higher absorption, and incidence and polarization insensitivity. The proposed metasurface absorber can be used for biomedical applications.

Modified Split Ring Resonators Sensor for Accurate Complex Permittivity Measurements of Solid Dielectrics.

In this paper, a sensor using modified Split Ring Resonators (SRRs) is designed, simulated, fabricated, and used for advanced investigation and precise measurements of the real part and imaginary part solid dielectrics’ permittivity. Adding vertical strips tightly coupled to the outer ring of the SRR leads to the appearance of two resonant frequencies at 1.24 GHz and 2.08 GHz. This modified geometry also assures an improved sensitivity. Using the full wave electromagnetic solver, both the unloaded and loaded sensors are investigated. The numerical simulations are used to develop a mathematical model based on a curve fitting tool for both resonant frequencies, allowing to obtain analytical relations for real and imaginary parts of permittivity as a function of the sample’s thickness and quality factor. The sensor is designed and fabricated on 1.6 mm thick FR-4 substrate. The measurements of different samples, such as transparent glass, acrylic glass, plexiglass, and Teflon, confirm that the modified SRR sensor is easy to implement and gives accurate results for all cases, with measurement errors smaller than 4.5%. In addition, the measurements highlight the importance of the second resonant frequency in the cases in which numerical limitations do not allow the usage of the first resonant frequency (1 mm thick sample).

Negative refraction metamaterial with low loss property at millimeter wave spectrum

The design of the millimeter-wave (MMW) metamaterials (MMs) unit cell operates at 28 GHz is presented and numerically investigated. The proposed structure composed of a modified split ring resonator (MSRR) printed on both sides of the substrate layer. Popular MM structures such as S-shape, G-shape, and Ω-shape are adjusted to operate at the 28 GHz for comparison purpose. MSRR achieves a wide bandwidth of 1.1 GHz in comparison with its counterparts at the resonance frequency. Moreover, the proposed structure presents very low losses by providing the highest transmission coefficient, S21, at the corresponding frequency region. The radiation loss is substantially suppressed and the negativity of the constitutive parameters of the proposed MM structure is maintained. By applying the principle of the electromagnetically induced transparency (EIT) phenomenon, the MSRR unit cell induces opposite currents on both sides of the substrate which leads to canceling out the scattering fields and suppresses the radiation loss. The constitutive parameters of the MM structures are retrieved using well known retrieval algorithm. The proposed structure can be used to enhance the performance of fifth generation (5G) antenna such as the gain and bandwidth.

Design and Research of Modified Split Ring Resonator for Reduction of Mutual Coupling in Microstrip Patch Antenna Array

In this document, we proved a new technique for eliminating the impact of mutual connection amongst elements in an antenna array by integrating the Metamaterial Hybrid Split Ring Resonator (HSRR). The HSRR suggested unit-cell consists of a single circular ring resonator, each rounded with two symmetrical divisions, with one hexagonal ring resonant. The insulation of over 13 dB without affecting the working frequency and radiation features shall be accomplished by integrating the HRSR metamaterial framework near the correct side of the standard radiating patsch of the antenna array running at 2.4 GHz. The efficiency of the HSRR antenna array proposed has been numerically assessed

Metagrating-enabled Brewster's angle for arbitrary polarized electromagnetic waves and its manipulation.

Brewster effect has attracted extensive interests through microwave to optical regime. However, previous work mainly focused on the cases with single linear polarization. We demonstrate in this paper an equal Brewster's angle for both TE (transverse-electric) and TM (transverse-magnetic) waves. Tunable Brewster effect is furthermore achieved. For practical implementation of this effect, we propose an anisotropic metagrating composed of modified split ring resonators (MSRR) as a proof-of-concept in X-band. Measurement results of the manufactured prototypes validate our method. The proposed metagrating featuring Brewster's angle manipulation potentially paves the way for many applications throughout the spectrum, e.g., angular selectivity.

Design of a modified single-negative metamaterial structure for sensing application

A new topology of modified negative effective permeability material (NEPM) are studied by adding a small similar form with different angles to the basic single split-ring resonators. We report our work conducted on the design, simulation and micro-fabrication of sensing system based on a modified split-ring resonator (MSRR) structure around 140 GHz operation frequency. Once the NEPM cells are excited, the reflection and transmission coefficients from the excitation mechanism can be measured by using quasi-optical technique with normal incidence. It has been shown that our proposal NEPM exhibits a high resonant frequency which is extraordinarily sensitive to the changes of the geometries and the properties of metal shape. By applying the new design of square Plus symbol (+) curve to the SRRs, more condensed size and higher sensitivity can be attained compared to conventional SRRs. Furthermore, the enhancement of sensitivity of the new design is also exposed. The considered sample double defect corner square modified form (DCD2) is fabricated in our lab using a conventional printed circuit board process with 2 μm aluminum and validated by comparing simulated profiles with measurements.

A Printed Xi-Shaped Left-Handed Metamaterial on Low-Cost Flexible Photo Paper.

A Xi-shaped meta structure, has been introduced in this paper. A modified split-ring resonator (MSRR) and a capacitive loaded strip (CLS) were used to achieve the left-handed property of the metamaterial. The structure was printed using silver metallic nanoparticle ink, using a very low-cost photo paper as a substrate material. Resonators were inkjet-printed using silver nanoparticle metallic ink on paper to make this metamaterial flexible. It is also free from any kind of chemical waste, which makes it eco-friendly. A double negative region from 8.72 GHz to 10.91 GHz (bandwidth of 2.19 GHz) in the X-band microwave spectra was been found. Figure of merit was also obtained to measure any loss in the double negative region. The simulated result was verified by the performance of the fabricated prototype. The total dimensions of the proposed structure were 0.29 λ × 0.29 λ × 0.007 λ. It is a promising unit cell because of its simplicity, cost-effectiveness, and easy fabrication process.

Sub wavelength plasmonic nano-antenna with modified SRR structure for Fano resonance

The optical electric field enhancement in the normal direction is noticed for Plasmonic and Fano mode at Nano antenna, therefore, we have modeled four various designs for Sub-wavelength Plasmonic and Nano-antenna with modified Split Ring Resonator (SRR) by adding new capacitors and SRR element to achieve the Fano resonance mode in various incident wave angles. Here, for all structures, the E-field enhancements at resonances are compared and design parameters effect on Fano resonance is debated. The incident wave direction is studied for making multi Fano resonance in all prototype structures and the extinction cross section comparison for 0°, 45° and 90° is revealed that the FANO resonances are related to the polarization angle of the incident wave and size of the gaps in Nano particles. SiN Substrate is selected with refractive index of 1.98 and silver with Johnson optical characteristic has been used for modeling of the metal layer. It has been observed that the |E2|/|Eint2| increased to 200000 at Fano resonances and the parametric studies showed that the gap size controls the Fano resonance frequency.

Multi-band phase shifter design using modified slotline configuration

In this paper, an analog multiband phase shifter using slotline configuration is proposed. To implement the design, a pair of modified Split Ring Resonator (SRR) is employed. The periodic property of SRR provides multiband characteristics, whether the coupling slot gives the phase variations over the bands. The operation is well explained with an equivalent circuit model and its characteristics have been studied both in simulation and measurement. The prototype operates in 1.77–2.16, 3.5–3.97, 5.08–5.33, 6.43–6.93, and 8.01–8.59 GHz frequency bands which can be utilized for GSM, GPS, WLAN, C-band, and X-band applications, respectively.

A negative index metamaterial antenna for UWB microwave imaging applications

In this article, a negative index metamaterial antenna is presented for ultrawideband (UWB) microwave imaging applications. Four left-handed (LH) metamaterial (MTM unit cells are located along one axis of the antenna as the radiating element. Each left-handed metamaterial unit cell assembles a modified split-ring resonator with a capacitance-loaded strip to obtain a design architecture that at a time shows both negative permittivity and negative permeability, which assures the stable negative refractive index to raise the antenna performance for microwave imaging. The antenna structure of dimension 16 × 21 × 1.6 mm3 is printed on low dielectric FR4 material with a slotted ground plane and a microstrip feed. Measured reflection coefficient illustrates that this antenna attains 114.5% bandwidth covering the frequency band of 3.4–12.5 GHz for a voltage standing wave ratio less than 2 with a maximum gain 5.16 dBi at 10.15 GHz. There is a stable harmony between simulation and measured results and improved nearly omnidirectional radiation characteristics within the operational frequency band. The stable surface current distribution, negative refractive index characteristic, considerable gain, and radiation property have made this proposed negative index metamaterial antenna distinguishable for UWB microwave imaging applications. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1352–1361, 2015

A Miniaturized Antenna with Negative Index Metamaterial Based on Modified SRR and CLS Unit Cell for UWB Microwave Imaging Applications.

A miniaturized antenna employing a negative index metamaterial with modified split-ring resonator (SRR) and capacitance-loaded strip (CLS) unit cells is presented for Ultra wideband (UWB) microwave imaging applications. Four left-handed (LH) metamaterial (MTM) unit cells are located along one axis of the antenna as the radiating element. Each left-handed metamaterial unit cell combines a modified split-ring resonator (SRR) with a capacitance-loaded strip (CLS) to obtain a design architecture that simultaneously exhibits both negative permittivity and negative permeability, which ensures a stable negative refractive index to improve the antenna performance for microwave imaging. The antenna structure, with dimension of 16 × 21 × 1.6 mm3, is printed on a low dielectric FR4 material with a slotted ground plane and a microstrip feed. The measured reflection coefficient demonstrates that this antenna attains 114.5% bandwidth covering the frequency band of 3.4–12.5 GHz for a voltage standing wave ratio of less than 2 with a maximum gain of 5.16 dBi at 10.15 GHz. There is a stable harmony between the simulated and measured results that indicate improved nearly omni-directional radiation characteristics within the operational frequency band. The stable surface current distribution, negative refractive index characteristic, considerable gain and radiation properties make this proposed negative index metamaterial antenna optimal for UWB microwave imaging applications.

Polarization insensitivity in square split-ring resonators with asymmetrical arm widths

A polarization-insensitive, square split-ring resonator (SSRR) is simulated and experimented. By investigating the influence of the asymmetrical arm width in typical SSRRs, we find that the variation of the arm width enables a blue shift of the resonance frequency for the 0° polarized wave and a red shift of the resonance frequency for the 90° polarized wave. Thus, the resonance frequency for the 0° polarized wave and the resonance frequency for the 90° polarized wave will be identical by asymmetrically adjusting the arm width of the SSRR. Two modified, split-ring resonators (MSRRs) that are insensitive to the polarization with asymmetrical arm widths are designed, fabricated, and tested. Excellent agreement between the simulations and experiments for the MSRRs demonstrates the polarization insensitivity with asymmetrical arm widths. This work opens new opportunities for the investigation of polarization-insensitive, split-ring resonator metamaterials and will broaden the applications of split-ring resonators in various terahertz devices.

Characteristics of Microstrip Fractal Antenna Shape Covered by Modified Split Ring Resonator

Metamaterials exhibiting negative index of refraction has attracted a great amount of attention in recent years. These materials are artificial structures that exhibit characteristics not found in nature. Microstrip antennas covered by metamaterial are one of the interesting areas of study. In this paper fractal shape antenna is proposed and covered by two layers of modified split ring resonator. The results shows an enhancement in Reflection Coefficients, gain, directivity and far field shapes.

Lowpass filter with large rejection through the entire W-band

A novel modified split ring resonator (MSRR) cell with compact dimension, wide stopband and deep transmission zeros is proposed. A relative experimental formula is induced. Then, a novel lowpass filter is designed by cascading three MSRR cells. Large rejection through the entire W-band is obtained by carefully choosing three transmission zeros of MSRRs in the lower, the middle and the higher frequencies, respectively. A rejection level of more than 35.89 dB is achieved from 75 to 110 GHz. In contrast, a high-low impedance lowpass filter is optimally designed with similar dimensions, the largest rejection of which is only 23.56 dB. It is even less than the least rejection level of our proposed filter.

Reconfigurable subwavelength waveguide based on magnetic metamaterial

The design and characterization is described of a reconfigurable subwavelength waveguide based on magnetic metamaterial. The waveguide is capable of reconfiguring its propagating mode from right-handed to left-handed, which can be applied in the design of novel microwave and RF devices such as leaky wave antennas with broadened scanning range. The waveguide consists of a rectangular metallic waveguide loaded by two pieces of different magnetic metamaterials, which are structured by the same cells—modified split ring resonators (MSRRs)—with different arrangements. Positions of the two pieces of metamaterials in the waveguide can be reconfigured separately by the control mechanism. The simulated transmission data show that the waveguide has a passband below the cutoff frequency of the hollow waveguide either in the left-handed case or in the right-handed case. The extracted constitutive parameters have demonstrated that the effective permittivity and permeability of the waveguide are simultaneously negative in the left-handed case and positive in the right-handed case. The magnetic field and surface current distributions in the waveguide confirm that the waveguide operates as can be expected. The influence of the control mechanism on the performance of the waveguide is studied. It is shown that the influence is so minor that it can be neglected.

Enhanced-Gain Microstrip Antenna Using Engineered Magnetic Superstrates

This letter presents a novel engineered magnetic superstrate designed to enhance the gain and efficiency of a microstrip patch antenna without any substantial increase in the profile of the whole structure (the antenna with the superstrate). The modified split ring resonator (MSRR) inclusions are used in the design of the engineered magnetic superstrate. Numerical full-wave simulations as well as analytical models are used to analyze the entire radiating system. Considering as an example a microstrip antenna operating within the UMTS band, the broadside gain of the antenna was improved by 3.4 dB and the efficiency was improved by 17% when using the engineered superstrate. The total height of the proposed structure, antenna with superstrate, is lambda0/7, where lambda0 is the free-space wavelength at the resonance frequency of the antenna.

An approach for small omnidirectional microstrip antennas based on the backward waves of double negative metamaterials

In this paper, a small omnidirectional microstrip antenna (MSA) is proposed based on a compact double negative (DNG) metamaterial, which is constructed by modified split ring resonators (MSRRs) and metal strips. First, the backward wave property of the DNG slab is investigated and illustrated by full-wave simulations. It is shown that the slab can exhibit double negative parameters and support backward wave in a broadband of 8.45 GHz∼11.05 GHz, so the existence of the DNG band is proven. Then the DNG unit cells are stacked and embedded into a host substrate to construct a phase-compensating substrate for the small MSA. By using the modified transmission line model (MTLM) and 3D full-wave simulation, a small MSA is modeled and characterized. Results show that the presence of the DNG fillings can indeed greatly reduce the physical dimensions from 0.5λ to 0.17λ, while its farfield pattern is significantly different from that of a conventional half-wave-length MSA. Lastly, the E-field distributions of the small MSA and a conventional half-wave-length MSA are contrasted and discussed to explain the functional mechanism of the small omnidirectional SMA.

Compact resonator for low temperature NMR experiments

We describe the design of a modified split-ring resonator, especially suited to low-temperature experiments, which enables cavities with dimensions of order 1 cm to resonate at frequencies as low as a few hundred megahertz.

A modified split-ring resonator probe for NMR imaging at high field strengths

A modified split-ring resonator probe for NMR imaging at high field strengths