GHz X-band Research Articles

Ultrathin and Flexible ANF/APP/PRGO Composite Films for High-Performance Electromagnetic Interference Shielding and Joule Heating

With the problem of electromagnetic interference (EMI) increasingly serious, the development of lightweight and flexible electromagnetic shielding composite films with excellent Joule heating performance and good mechanical properties is of great significance for modern electronic devices. In this study, we prepared aramid nanofiber/aramid nanofiber-poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)/polydopamine-modified reduced graphene oxide (ANF/APP/PRGO) composite films with excellent electromagnetic shielding properties and electrical heating properties by stepwise vacuum filtration. With high conductivity (124.10 S/cm) and multi-interface electromagnetic wave reflection caused by the layered structure, the composite films achieve an EMI shielding effectiveness (SE) as high as 40.52 dB at 8.2–12.4 GHz (X-band) with a low thickness (∼22 μm). At the same time, the composite films also exhibit excellent electrical heating performance with fast response and cycle stability, which can reach a surface saturation temperature as high as 127.6 °C under an applied voltage of 7 V. Therefore, it can be envisaged that the ANF/APP/PRGO composite films have certain practical application value in the fields of electromagnetic shielding and electric heating.

Triple Band-Notch UWB Antenna Embedded with Slot and EBG Structures

In this paper, a planar, compact pentagonal shaped ultrawideband antenna of microstrip line fed offering triple band-notched characteristics response is proposed and investigated. Triple band-notch response can be achieved by creating two inverted U-shaped slots of different size in pentagonal patch, and also electromagnetic band gap structure of hexagonal shape is created near the feed line of UWB antenna. To implement the proposed antenna, RT/DUROID 5880 substrate of 1.6 mm thickness is used. The designed antenna was successfully simulated, developed, and manufactured. The dimension of the suggested antenna is 36 mm × 33 mm × 1.6 mm and has a bandwidth of 3.1–10.6 GHz with a magnitude of S 11 < − 10 dB , the maximum pass band gain of 4.6 dB and with the exception of the 4.0–4.4 GHz (C-band satellite communication), 5.2–5.8 GHz (WLAN), and 8.0–8.25 GHz (X-band) frequency bands. The suggested antenna has a good return loss, a virtually omnidirectional radiation pattern, and a constant gain throughout operation.

A Single-Layer S/X- Band Shared Aperture Antenna with MIMO Characteristics at X-Band for Airborne Synthetic Aperture Radar Applications

New frequencies can be supported with very effective space use by using the shared aperture antenna This work presents on designing a dual-banddual-polarized (DBDP) S/X-band shared aperture antenna (SAA) for synthetic aperture radar (SAR) applications operating at S-band frequency (3.2 GHz) and X-band frequency (9.65 GHz). The single-layer SAA DBDP S-band antenna is designed in a square-shaped patch with coaxial feeding in both vertical and horizontal polarization. The X-band antenna design is in 1 × 3 vertical series with microstrip feeding and arranged at four corners of the proposed antenna. The S-band antenna is mainly used for airborne applications such as air traffic control and surface ship radar. In contrast, the X-band antenna application is maritime vessel traffic control, defense tracking, and vehicle speed detection for law enforcement. To verify the antenna, a prototype is fabricated and measured with s-parameters. The proposed design exhibits that the gain of the S-band is 7.2 dB and for the X-band is 12.4 dB, and the isolation is achieved more than −35 dB, and for this antenna, we achieved a bandwidth of 0.12 GHz for S-band and 0.27 GHz for X-band. However, the X-band antenna is a multi-input and multioutput antenna that is to be validated by using MIMO characteristic parameters such as envelope correlation coefficient (ECC), diversity gain (DG), channel capacity loss (CCL), mean effective gain, and mutual coupling. The MIMO characteristic parameter of X-band antenna values is found to be in a similar manner to both simulated and measured values. For this X-Band antenna, ECC, DG, CCL, and mutual coupling were achieved as below 0.05, 9.5 dB, 0.5 bps/Hz, and −30 dB to −55 dB, respectively. The total size of the antenna is 100 mm × 100 mm × 1.6 mm.

A Quadruple Notch UWB Antenna with Decagonal Radiator and Sierpinski Square Fractal Slots

A novel quadruple-notch UWB (ultrawideband) antenna for wireless applications is presented. The antenna consists of a decagonal-shaped radiating part with Sierpinski square fractal slots up to iteration 3. The ground part is truncated and loaded with stubs and slots. Each individual stub at the ground plane creates/controls a particular notch band. Initially, a UWB antenna is designed with the help of truncation at the ground plane. Miniaturization in this design is achieved with the help of Sierpinski square fractal slots. Additionally, these slots help improve the UWB impedance bandwidth. This design is then extended to achieve a quadruple notch by loading the ground with various rectangular-shaped stubs. The final antenna shows the UWB range from 4.21 to 13.92 GHz and notch frequencies at 5.02 GHz (C-band), 7.8 GHz (satellite band), 9.03, and 10.86 GHz (X-band). The simulated and measured results are nearly identical, which shows the efficacy of the proposed design.

Improved fracture response and electromagnetic interference shielding effectiveness of cementitious composites incorporating pyrolytic bagasse fibers and pine needles

The increasing amount of bagasse and pine needles have become a potential environmental threat to humans and wildlife, as they have serious consequences of catching fire or dumping on land. These wastes have been transformed for the first time into nano carbonaceous inerts via pyrolysis at 500 °C and 700 °C, respectively, in an inert atmosphere and utilized in the preparation of cementitious composites, to improve their strength, fracture response, and electromagnetic interference shielding. The pyrolysis temperature was decided based on thermogravimetric analysis of the selected Agro-wastes. Carbonized material produced by pyrolysis was ground to nano level and characterized through X-ray diffraction analysis, scanning electron microscopy, energy dispersive X-ray spectroscopy, Raman spectroscopy, laser granulometry, and UV–visible spectroscopy. Samples of cement mortar with cement to the sand ratio of 1:1.5 were prepared with the addition of 0.025 %, 0.05 %, 0.08 %, 0.20 %, 0.50 %, and 1.00 % pyrolyzed nano-inerts by wt. of cement after the effective dispersion in water. The uniform dispersion of carbonized particles in cementitious matrix was evidenced through the forensic analysis. Three-point bending test of mortar prisms was conducted at 0.1 mm/min strain rate in strain-controlled mode and the broken halves were tested in compression. A maximum increment of 25.36 % in compressive strength and 15.83 % in flexural strength was achieved due to the addition of 0.20 % pyrolyzed bagasse fibers and 1.00 % pyrolyzed pine needles respectively. A substantial increase of 114.15 % and 101.88 % was achieved in fracture toughness with the addition of 0.20 % carbonized bagasse fibers and 1.00 % carbonized pine needles, respectively. The improvement in strength and ductility is associated with supporting mechanics of crack branching, bridging, and crack contouring verified via SEM micrographs. The inertness of pyrolyzed particles in cementitious composites was verified by X-ray diffraction analysis. Furthermore, the cementitious samples were tested within the frequency range of 8–12 GHz in x-band to check electromagnetic interference shielding effectiveness (EMI-SE), and maximum improvement of 18.02 dB and 20.06 dB was attained with 0.50 % intrusion of pyrolytic bagasse fibers and pine needles, respectively.

A 5G rotated frame radiator for ultra wideband microwave communication

AbstractA 5G rotated frame radiator for multiple applications is presented in the following paper. The presented geometry is capable of radiating the large frequency band from 2.91 to 12.17 GHz, which covers the 5G-(I) sub-6 GHz band, X-band communication with high efficiency. The impedance bandwidth of the radiator is 128%, with an electrical size of 0.24 λ × 0.24 λ × 0.15 λ in lambda. The antenna is simulated with an FR4 substrate using CST Simulator. 06-stages evolution process is also investigated by simulations, and corresponding S-parameter results are presented. Antenna's design comprises a patch in a rotated square fractal-like frame fed by a microstrip line. The proposed structure also demonstrates stable radiation patterns across the operating bandwidth. The proposed radiator has a high gain of 3.8 dBi, and an efficiency of 85%, which claimed that UWB range of the designed antenna. Therefore, it is useful for 5G-(I) sub-6 GHz band, X-band applications, including mobile, radar, and satellite microwave communication.

Atomic oxygen exposure effect on carbon nanotubes/epoxy composites for space systems

Structural, optical and EMI shielding properties of epoxy resin reinforced with carbon nanotubes fillers “Taunit-M” and “Taunit-MD” have been studied. To estimate the resistance of nanocomposites operating in low-Earth orbits, the samples were exposed to atomic oxygen (AO) in the fluence range of (1.7–30) × 1020 cm−2. AO exposure results in mass loss of epoxy resin with carbon fillers: the erosion yields (Rm) are 1.07 × 10−23 g/atom and 1.21 × 10−23 g/atom for “Taunit-M″ and “Taunit-MD”, respectively. Diffuse and specular reflectance noticeably decreases after AO exposure which in their turn leads to increase of solar absorptance from 0.940 to 0.996 for “Taunit-M″ and from 0.944 to 0.992 for “Taunit-MD”. AO exposure also results in reduction of EMI shielding effectiveness from ∼5 dB to ∼4.2 dB and ∼4.96 dB for epoxy resin with “Taunit-M″ and “Taunit-MD”, respectively, in the frequency range of 8.2–12.4 GHz (X-band) at room temperature.

Dielectric characterization studies of hydrogen-bonded polar liquids in nonpolar medium using cavity perturbation technique

The dielectric characteristics of polar substances like propan-1-ol, propionaldehyde, isopropyl amine & its equimolar ternary mixtures in benzene are examined at discrete microwave frequency region using the cavity perturbation technique at 6.218 GHz (J-band), 9.880 GHz (X-band), 16.331 GHz (P-band) and 24.951 GHz (K-Band) at room temperature. The minimum energy geometry optimization is performed at 6-311G+ (d, p), 6-311G++ (d, p) basis set with DFT(B3LYP) method for both pure as well as ternary mixtures of propan-1-ol, propionaldehyde & isopropyl amine liquid systems. The dipole moment(s) of these combinations are evaluated using Higasi's approach and verified with theoretical data. The average relaxation times of the ternary solutions are calculated using the Cole-Cole plots. The mean molecular polarizability values of distinct systems of propan-1-ol, propionaldehyde, isopropyl amine, and their ternary solutions are calculated with Lippincott-δ function model. The findings are described through the molecular association between the components by hydrogen bonding.

Electromagnetic Band Gap based compact UWB Antenna with Dual Band Notch Response

In Antenna Technology, Electromagnetic Band Gap (EBG) structures are one of the mostly used structures to improve gain of antenna, suppress surface waves and band notching. In UWB frequency spectrum more number of small frequency bands are exists and these bands cause electromagnetic interference, to reject such bands more number of EBG structures are required. Due to limited monopole antenna's ground plane, it is required to have EBG with small in size and single EBG to reject two or more bands. The simulated results of proposed new C-shaped EBG by placing near the feedline of fork-shape Ultra-Wide Band (UWB) antenna to reject two bands namely Lower Wireless Local Area Network(L-WLAN) band range from 5.15 GHz to 5.35GHz and X-band of satellite downlink communications networks (7.25GHz –7.75GHz) within a UWB antenna's spectrum and EBG occupying less area compared with the reported Conventional Mushroom Type (CMT) EBG, semi-circular EBG, slotted-patch ELV EBG and TVS EBG. Fabrication and measurement results of the newly proposed antenna attain an enormous bandwidth i.e., from 2.8 GHz to 11.5 GHz while eliminating frequency bands between 5.15 GHz to 5.35 GHz (Lower WLAN) & 7.25GHz to 7.75GHz (X-band of satellite downlink).

MXene-decorated carbonized jute composite for high-performance electromagnetic interference shielding

Lightweight, good processability and efficient electromagnetic interference (EMI) shielding materials have captured more interest with the recognition of electromagnetic pollution hazards. Biomass-based carbon has been considered as a promising EMI shielding due to its low cost, renewability and environmental friendliness. Here, we used jute felt as the precursor of biomass carbon to fabricate the MXene (Ti3C2Tx)/jute composite (MXene/CJ) via a simple carbonization process and dip-and-dry method. Higher carbonization temperature and more MXene loading are conducive to electrical conductivity and shielding effectiveness (SE). When the carbonization temperature was 900 °C and dip-and-dry times was 3, the average EMI SE of 59.08 dB was achieved in 8.2–12.4 GHz (X-band) with a reflection-dominated mechanism. Besides, the composite also exhibits the potential to be used as a strain sensor. Under small pressure, the composite possessed excellent sensitivity and response time. The wrist bending, swallowing and vocal cord vibration can be monitored in real-time. These results illustrate that the MXene/CJ composite has a broad prospect in the EMI shielding and wearable electronics fields. This work also provided a feasible approach for the high-value utilization of natural biomass resources.

The ferromagnetic resonance (FMR) of SrZ hexaferrite (Sr3Co2Fe24O41), and the tuning of FMR with an external magnetic field

The hexagonal Z-type ferrite Sr3Co2Fe24O41 (SrZ) was first synthesised in 2001 and reported as being a room temperature multiferroic material in 2010, with subsequent investigations into its multiferroic properties, but little into high frequency and microwave properties, and ferromagnetic resonance frequency (FMR), which determines its ability as an electromagnetic (EM) absorber and radar absorbing (RAM) stealth material. It was shown that SrZ existed as a majority or single phase after heating in a narrow temperature range between 1170 and 1190 °C using X-ray diffraction (XRD) and measurement of magnetic hysteresis loops, with the sample appearing to be single phase SrZ at 1190 °C. We measured complex permeability and permittivity of a single phase polycrystalline ceramic sample of SrZ between 500 MHz and 8 GHz (X-band). The sample had a relatively high permittivity >17 over this entire frequency range, and it showed a strong ferromagnetic resonance (FMR) at 2.3 GHz. This FMR could also be tuned by the effect of an external magnetic field, by moving a simple bar magnet progressively closer to a toroidal sample. This incurred a very slight shift in the peak up to 2.48 GHz at distances of 2.5–10 cm from the sample – a tuning of ∼5–6% with applied magnetic fields estimated to be 0.11–0.23 T, which is not insignificant. At a close distance of 0.5 mm we got a high degree of tuning of FMR to 3.4 GHz, a large change of 1.07 GHz (= 46% increase) with an applied magnetic field estimated to be 0.40 T. Despite this, the applied field had no significant effect on permittivity over 0.5–8 GHz. Such results have never been reported before, and are significant, as this would enable tuning of the FMR via simple physical/mechanical movement of a bulk alloy magnet, effectively creating a tuneable microwave filter or absorber.

Superhydrophobic graphene nanowalls for electromagnetic interference shielding and infrared photodetection via a two-step transfer method

The growing need for flexible electronic devices has triggered substantial research efforts toward multifunctional surfaces. Herein, flexible and superhydrophobic surfaces based on micro-nanoscale two-tier structures were prepared by combining graphene nanowalls (GNWs) with UV-curable adhesive polymer using a two-step transfer method. These GNWs/UVA surfaces show excellent superhydrophobic properties with a water contact angle (CA) above 170° and a rolling angle (RA) below 5°. The superhydrophobic properties are retained with extreme liquid repellency even after thousand times of bending. The surfaces are highly conductive (conductivity > 3000 S/m) and provide excellent electromagnetic interference (EMI) shielding effect over the range of 8.2–12.4 GHz (X-band). Moreover, the surfaces exhibit high average infrared (IR) absorption up to 85 % in the range of 2–20 μm, indicating good performance in IR shielding. Furthermore, a long-wave IR photodetector with flexible hydrophobic GNWs/UVA was prepared, which has a responsivity of 28 μA/W at room temperature. The IR photodetector also has good water resistance stability. The methodology reported here provides a new route to fabricate micro-nano structures for multifunctional superhydrophobic surfaces. It has great potential for myriad applications in commercially viable flexible electronics, EMI protection, and IR photodetection.

A Triple-Band Reflective Polarization Conversion Metasurface with High Polarization Conversion Ratio for Ism and X-Band Applications.

A compact and triple-band polarization converting reflective type metasurface (PCRM) with a high polarization conversion ratio (PCR) is proposed for strategic wireless antenna-integrated applications. The unit cell of the metasurface is composed of S- and G-shaped patches separated with a parasitic gap and the grounded via is connected to the full ground plane. The unit cell is etched on an FR4 substrate (dielectric constant, εr = 4.4, loss tangent, tan δ = 0.02), with compact dimensions of 10 mm3 × 10 mm3 × 1.6 mm3. This structure provides a resonance at 5.2 (ISM), 6.9, and 8.05 GHz (X-band) frequencies. The designed unit cell structure is studied for Transverse Electric (TE)/Transverse Magnetic (TM) incident waves and their responses to the various incident angles. The corresponding PCR is calculated, which shows 92% in the lower frequency band (5.2 GHz), 93% in the second frequency band (6.9 GHz), and 94% in the high-frequency band (8.05 GHz). The total efficiency of the structure shows 83.2%, 62.95%, and 64.6% at the respective resonance bands. A prototype of the proposed PCRM with 3 × 3 unit cells is fabricated to validate the simulated results. The experimental data agrees with the simulation results. The compactness, triple-band operation with a high PCR value of more than 92% makes use of the designed metasurface in wireless antenna-integrated applications at ISM and X-bands.

Construction of SnO2 nanoparticle cluster@PANI core-shell microspheres for efficient X-band electromagnetic wave absorption

Superior electromagnetic (EM) wave absorption properties in 8.2–12.4 GHz (X-band) can be obtained via the effective combination of polyaniline (PANI) and SnO 2 nanoparticle cluster. In this work, SnO 2 nanoparticle cluster@PANI (SnO 2 @PANI) core-shell microspheres were firstly fabricated via a hydrothermal process followed by in-situ polymerization, and the EM wave absorption properties of SnO 2 @PANI core-shell microspheres in X band were studied. The related structure and morphology analyses indicated SnO 2 @PANI core-shell microspheres were successfully synthesized with PANI coated on the surface of SnO 2 nanoparticle cluster. The minimum reflection loss (RL min ) of − 69.1 dB (thickness of 2.78 mm) and effective absorption bandwidth (EAB) covering the whole X-band (when the thickness was from 2.5 to 3.1 mm) was achieved. Remarkable EM wave absorption properties of SnO 2 @PANI core-shell microspheres were mainly attributed to the outstanding impedance matching characteristic and dielectric loss capability (conduction loss, interfacial polarization loss and dipole polarization loss). • SnO 2 @PANI core-shell micropheres have been synthesized via a hydrothermal process followed by in-situ polymerization. • The excellent reflection loss of SnO 2 @PANI core-shell micropheres is − 69.1 dB with a matching thickness of 2.78 mm. • The effective absorption bandwidth of SnO 2 @PANI core-shell micropheres could cover the whole X-band.

Fabrication of a highly efficient multilayer microwaves insulator based on CuFe2O4/(Pb1−xLax)/(Zr1−yTiy)O3 (composite: 7/60/40) (0 ≤ x, y ≤ 1) and Cu-doped g-C3N4 nanograins

Nowadays, microwave pollution is a major concern around the world. Therefore, the construction of multilayer microwave absorbers with low thickness and wide bandwidth has been investigated. A novel multilayer broadband microwave insulator with high performance containing fillers comprised of copper ferrite spinel (CuFe2O4) nanograins (NGs), lead zirconium titanate ceramic (Pb1−xLax)(Zr1−yTiy)O3 (composite: 7/60/40) (0≤x,y ≤ 1) (PLZT) nanoparticles (NPs), and copper-doped carbon nitride graphitic (Cu-doped g-C3N4) nanosheets (NS) based on epoxy resin has been successfully prepared. The crystal structure and morphology of synthesized nanograins were specified using XRD, SEM, and EDX/mapping analysis. In addition, the microwave absorption properties of the resulting multilayer microwave insulator were evaluated using a vector network analyzer (VSM) in the frequency range of 8–12 GHz. Response surface methodology (RSM) was applied to the design of experiments to reduce the experimental time and cost, and obtain the optimal conditions. The weight percentage (wt.%) of CuFe2O4 magnetic nanograins, (Pb1−xLax)(Zr1−yTiy)O3 (0 ≤ x,y ≤ 1) dielectric NGs, Cu-doped g-C3N4 electric conductivity nanosheets, and thickness of the designed insulators were optimized using the RSM method to attain a multilayer microwave insulator with the optimal microwaves absorption efficiency. The minimum reflection loss (maximum absorption efficiency) was determined to be < –30 dB (absorption >99.9%) for the optimized multilayer microwaves insulator under the conditions of 3.0 wt% CuFe2O4 magnetic nanoparticles, 5 wt% (Pb1−xLax)(Zr1−yTiy)O3 (0≤x,y ≤ 1) dielectric NGs, 1.0 wt% Cu-doped g-C3N4 electric conductive nanosheets with 1 mm thickness in the microwave frequency range of 8–12 GHz (X-band). The highest attenuation coefficient (>500 dB/m) showed that the microwaves energy was weakened. In addition, the minimum reflection coefficient (maximum transmission coefficient) was calculated to be ∼0.01 (RL = −35 dB, AL = 99.99%). Finally, the obtained results show that these factors and their levels were correctly selected for the fabrication of high-performance multilayer microwave insulators.

Electromagnetic Attenuation Performance of Sustainable e-Textile Derived from Polypyrrole Impregnated Jute Fabrics with Predominant Microwave Absorption

ABSTRACT The proliferation of electromagnetic (EM) pollution is more rapid now and can be more outrageous in near future due to the exponential growth of the electronics industry. Strategy of using natural fibers for fabricating efficient EMI shielding materials is an environmentally benign solution for this serious peril. With this motivation, we are introducing novel e-textile derived from sustainable jute fabrics that are capable of suppressing and absorbing EM radiations in the frequency range 8.2–12.4 GHz (X-band). In the present work, jute fabrics were in-situ polymerized with pyrrole monomer. These conductive fabrics were then characterized and correlated for their structure, morphology, thermal stability, electrical conductivity, and EMI shielding capabilities. Moreover, this e-textile showcased excellent electrical conductivity of 1.160 S/cm and exhibited a maximum EMI shielding effectiveness value of −30.2 dB (>99.9% blockage) at 1 mm fabric thickness by a predominant absorption behavior with menial reflection or secondary pollution, which is highly beneficial for commercial applications. This is so far the first report of jute fabrics as e-textile with the highest shielding efficacy value reported, which makes them an ideal candidate for next generation of smart and wearable electronic textiles for futuristic applications such as robotics and artificial intelligence (AI).

Electrochemical deposition assisted the construction of titanium carbide@polyaniline hybrid in waterborne polyurethane conductive network for improved electromagnetic interference shielding and flame retardancy

To solve the increasing serious electromagnetic radiation pollution and limitations of metal-based electromagnetic shielding materials in flexible devices, the polyaniline (PANI) is deposited on the surface of two-dimensional Ti3C2 to obtain the Ti3C2@PANI hybrid for constructing waterborne polyurethane (WPU) composite. Meanwhile, to address the flame risk of WPU composite, the two-dimensional black phosphorous (BP) is incorporated as a flame retardant to prepare isolated flame-retardant black phosphorous-waterborne polyurethane/Ti3C2@polyaniline(Q-FBP-WPU/Ti3C2@PANI) composite with isolated structure. Due to the existence of conductive fillers and the isolated structure, the Q-FBP-WPU/Ti3C2@PANI composite exhibited the highest electrical conductivity (2.23 S/m) and the electromagnetic shielding effectiveness (EMI SE) of 27.3 dB in the frequency range of 8.2–12.4 GHz (X-band) and retains higher than 20 dB after hundreds of stretching and bending, which completely satisfies the commercial demands. Compared with the composite with a disordered structure, the thermal conductivity of Q-FBP-WPU/Ti3C2@PANI is increased by 93.3%. The cone test results show that the peak heat release rate, total heat release, total smoke production and total CO production of Q-FBP-WPU/Ti3C2@PANI is decreased by 46.2%, 16.3%, 21.2% and 15.5% than that of pure WPU, certifying the fire safety of WPU are greatly improved. This work supports a novel and applicable idea for constructing functional electromagnetic shielding materials.

A Compact Dual-Band Self-Diplexing MIMO Patch Antenna for ISM and X-Band Communications

A compact, dual-band, and self-diplexing MIMO patch antenna with a shared aperture is presented for Industrial scientific medical (ISM) band and X-band communications. The structure consists of two orthogonal feed lines and a rectangular slot in a square patch. The size of the FR4 substrate is 50 × 50 × 1.6 mm3. The designed structure operates at 5.8 (ISM) and 8 GHz (X-band) frequencies independently with a simulated peak gain of 5.46 and 3.59 dBi respectively. A 13 dB of isolation is obtained for the two orthogonal ports. The obtained frequency ratio range is 1.20-1.33 over the reflection bandwidth. The design structure is fabricated and validated experimentally. The compactness and promising performance in terms of low ECC (Envelope Correlation Coefficient) (<0.1), high peak gain can make the proposed antenna a choice for current wireless devices.

Flexible interconnected 4-port MIMO antenna for sub-6 GHz 5G and X band applications

A flexible 4-port 4-element interconnected MIMO antenna is proposed for Sub-6 GHz 5G and X-band applications. The 4-element structure attains a low profile of 0.612λ2 (at 3.34 GHz) through careful placement of antenna elements. The elementary antenna top side is formed of an inverted E and inverted L-shaped conductive structure attached to both sides of the central feed line. Two hollow tilted square-shaped assemblies are added horizontally with the inverted L for performance enhancement. The bottom plane consists of a truncated ground with a vertical stub on the side for achieving wideband performance. The MIMO configuration along with polarization diversity is attained by positioning the elementary antenna symmetrically in a sequential rotational manner. The interconnection between ground planes is ensured by placing an I-shaped strip which is further modified by adding a slotted rectangular stub on the central vertical line for better isolation. The flexible antenna demonstrated minimum efficiency and maximum gain of 70% and 4 dBi, respectively in addition to accomplishing a bandwidth of (40%) 3.34–5.01 GHz and (3.31%) 8.9–9.2 GHz while satisfying the MIMO diversity performance in terms of envelope correlation coefficient (ECC) < 0.17. Finally, the antenna performance in terms of S-parameters and MIMO diversity parameters are tested by bending the antenna along the X and Y axis that demonstrated decent performance thus making the MIMO antenna worthy for its use in Sub-6 GHz 5G and X Band Applications with tight space requirements.

RADAR ABSORBING MATERIALS

Carbon nanotubes (CNT) were functionalized with ethanol, nitric and sulfuric acid. From the obtained nanocomposites, electrical permittivity, magnetic permeability and reflectivity complex parameters were studied in the frequency range of 8.2 to 12.4 GHz (X-band). The results of reflectivity for nanocomposites, functionalized with CNT, showed an attenuation of - 21 dB and -18 dB, at the frequency of 10.4 GHz and 12.4 GHz, respectively, with approximately 99% of attenuation, demonstrating, then, that they are promising for application as Radar Absorbing Materials (RAM).