X-band Frequency Research Articles

Comparison between Two Different Fractal Koch Position for Reflecting Intelligent Surface (RISs)

The paper focuses on investigating the fractal shape placement of metasurface reflectors at the X-band frequency for Reflecting Intelligent Surface (RIS). The proposed reflector adopts a square shape, with the fractal intersection on a Rogers RO5880 substrate measuring 0.51 mm in thickness. The graph illustrating the S-parameter and reflection phase exhibits the simulated outcomes for various fractal positions. Furthermore, the bandwidth of the proposed reflector was determined by analyzing the simulation results. The impact of the incident wave angle on the proposed reflector was observed to shift along the horizontal axis. Mainly, the reflector with the inward fractal shape position demonstrated better performance and a wider bandwidth compared to the outward fractal substrate.

Electromagnetic shielding enhancement in cement composites: a comparative study of mechanically and thermally recycled carbon fibers

Abstract The recycling of carbon fibers that have reached the end of their service life and their reintegration into new applications hold significant importance from an environmental and sustainable perspective. In this study, the aim is to enhance the electromagnetic wave shielding properties of cement-based composites by incorporating mechanically and thermally recycled and ball-milled carbon fibers at volumetric ratios of 1%, 2%, and 3%. Electromagnetic tests are conducted in the X-band frequency range (8-12.5 GHz), commonly preferred for microwave applications. The obtained results demonstrate an improvement in the SEA (absorption loss )and SET (total power loss) values of the composite with the use of recycled fibers. This improvement is particularly more pronounced in composites containing thermally recycled fibers. The enhanced performance is attributed to the electrical conductivity imparted by carbon fibers. At a frequency of 11.9 GHz, the SET value increased from 8.5 dB for the control sample to 9.2 dB for composites with 3% mechanically recycled fibers and up to 19 dB for composites with 3% thermally recycled fibers. These findings indicate that using recycled carbon fibers enhances the electromagnetic wave shielding properties, with thermal recycling contributing more significantly to this enhancement.

Manganese–cobalt ferrite and polyaniline core–shell nanocomposite as an efficient shielding material against electromagnetic interference under X-band frequency

Manganese–cobalt ferrite and polyaniline core–shell nanocomposite as an efficient shielding material against electromagnetic interference under X-band frequency

Enhanced Electromagnetic Interference Shielding in Cement Composites Utilizing Carbon Fiber Clustered Networks with Dual Different Lengths

Electromagnetic interference (EMI) shielding is crucial for radio frequency ranges, particularly around 1 GHz, to ensure the functionality and security of electronic devices and wireless communications especially within building materials. The inherent properties of typical metallic materials, such as their heavy weight and high cost, make them less suitable for mass production, particularly in the construction applications. Herein, we present a novel approach to improve EMI shielding efficiency of cement composites by incorporating two types of carbon fibers with distinct lengths as fillers and optimizing the clustering network among these fillers. By precisely controlling the length and proportion of long (mother) and short (anchor) carbon fibers, we demonstrate that a 7:3 ratio of 6 mm mother fibers to 2 mm anchor fibers yields optimal shielding efficiencies, delivering 65.3 dB at a low radio frequency (1 GHz) and 44.5 dB in the high X-band frequency range (8.2 – 12.4 GHz). Significantly, two-dimensional matrix simulations corroborate the geometric modifications occurring between fillers as the length and ratio of carbon fibers are altered, showing excellent agreement with our experimental results. Combined with an intriguing approach to fine-tune the clustered network of carbon fibers, this study highlights the critical role of filler geometry within the matrix in developing high-performance EMI shielding materials, offering new insights for the design of advanced EMI shielding solutions.

Dielectric and Emissivity Behavior of Soil of Rehand River of Surajpur Chhattisgarh at X-Band Microwave Frequency

Abstract: Microwaves are a form of electromagnetic radiation consisting of electric and magnetic fields oriented at right angles to one another. They operate within a frequency range of approximately 0.3 GHz to 300 GHz, corresponding to wavelengths from 1 meter to 1 millimeter. This paper explores a theoretical model for estimating the emissivity and dielectric constant of soil samples as they relate to moisture content. The emissivity of these soil samples was measured at X-Band frequencies for both vertical and horizontal polarizations. The results indicate that emissivity is higher for vertical polarization than for horizontal polarization. Additionally, the dielectric constant shows a gradual increase with rising moisture content.

Experimental and Simulated Investigation of S-parameters and Power Loss Characteristics of PTFE/Glass Composites at X-band Frequency

Polytetrafluoroethylene (PTFE)-based substrates are in high demand for high-frequency (microwave) applications because of their low relative permittivity, enabling efficient signal transfer. In this work, PTFE composites have been prepared with different content (5 wt.% - 25 wt.%) of soda lime silica glass (SLSG) for substrate application. The composites were characterized by their complex permittivity and S-parameters through the rectangular waveguide (RWG) measurement method over x-band frequency (8.2 GHz – 12.4 GHz). The RWG set-up was connected to a vector network analyser for the characterization. Power loss of the composites due to material absorption was calculated using the measured S-parameters. As the content of the SLSG increased from 5 - 25 wt.%, complex permittivity rose from 2.18-j0.0035 to 2.56-j0.0047 in the frequency range considered. In addition, |S11| reduced from 0.623 and 0.700 to 0.418 and 0.441, whereas |S21| varied from 0.780 and 0.713 to 0.906 and 0.895 for 5 wt.% and 25 wt.% SLSG contents at 8.2 GHz and 12.4 GHz, respectively. The calculated power loss increased from 2.94 dB to 3.29 dB and 4.01 dB to 4.88 dB for the same filler contents and frequency. Furthermore, the S-parameters were simulated using the finite element method (FEM) via COMSOL software and compared with the measured values. The comparison revealed a mean relative error of < 0.1, denoting the accuracy of the RWG method. Also, the electric field distribution across the waveguide length was visualized. Thus, the optimal performance of the composite was found at 5 wt.% SLSG filler content for microwave substrate application.

Synergistic effects of carbon black and electrospun FKM fibers for superior EMI shielding

Technological advancements have exacerbated electromagnetic interference (EMI), necessitating superior shielding materials. This study details the creation of lightweight, flexible fibrous coatings composed of fluoroelastomer (FKM) integrated with conductive carbon black (CB), utilizing electrospinning. The EMI shielding performance of the resultant composite was thoroughly evaluated using the OATS (open area test site) method within the X-band frequency range. Empirical data indicate that the FKM/CB composite fibers achieved excellent shielding performance, with an average shielding effectiveness of −69 dB and a peak of −72 dB at 8.4 GHz. The composite also demonstrated significant radar cross-section (RCS) reduction, enhancing its stealth capabilities and making it a prime candidate for defense applications.

Multifunctional Mxene-Infused Textile Toward Energy Harvesting, EMI Shielding, Flame Resistance, and Joule Heating with Thermo-Chemo-Mechanical Robustness

The increasing demand for wearable devices and mobility platforms has garnered the importance of multifunctional components that integrate various features. To achieve this multifunctionality, the carbon-based two-dimensional nanomaterial Mxene (Ti₃C₂Tx) has been explored in various studies including smart textiles, owing to its high electrical conductivity, hydrophilicity, and abundance of functional groups. But the limitations of MXene applications are its low mechanical durability and flexibility, as well as its vulnerability to moisture and washing, which restrict its use in wearable smart textiles. In this study, we developed a novel type of multifunctional smart textile that incorporates energy harvesting, electromagnetic interference (EMI) shielding, flame resistance, and Joule heating. By integrating these functions, the synergy between them could maximize the benefits of the smart textile. MXene, polyvinyl alcohol (PVA), and polyacrylic acid (PAA) were cross-linked through sonication and a vortex generator, and this mixture was vacuum-filtered onto Hanji, a traditional Korean paper, to create a fiber with an asymmetric structure via a simple yet efficient process. Various analytical techniques confirmed the successful cross-linking of MXene/PVA/PAA (MPP), ensuring the fabrication of MXene/PVA/PAA-Hanji (MPP-H) textiles. Structural integrity and stable interfaces were confirmed through a series of experiments, and the performance of the multifunctional capabilities was evaluated.In terms of the functionalities, The MPP-H fiber demonstrated the capability to generate power for over 1 h with the application of a small amount of electrolyte solution, producing a power density of approximately 100 µW/cm³. Additionally, it exhibited a high shielding effectiveness per unit thickness (SE/t) of up to 437 dB/mm within the X-band frequency range (8.2–12.4 GHz), indicating excellent shielding performance relative to its thickness. With an absorption shielding rate exceeding 90%, the developed textile was proven to be an absorption-based shielding material. Furthermore, the MPP-H displayed superior thermal and mechanical properties, including excellent flame retardancy, rapid Joule heating, durability through wash tests, and sonication resistance, making it practical for real-world applications.The MPP-H textile efficiently integrates multiple functionalities into a single material, making it a promising candidate for next-generation wearable devices and mobile technologies.

Si/Graphene exotic type IMPATT (p+-n-n+-) Opto-sensor: First experimental observation

On-chip DC characterization study has been performed on exotic-type Si/Graphene Avalanche Transit Time (ATT) device for ultra-fast optical-sensing. The performance of the newly proposed device has further been compared with conventional narrow and wide band gap semiconductor based p+-n-n+ devices. It has been observed that at X-band frequencies, the new class of device outperforms Si/SiC/GaN and their heterostructure counterparts, in terms of better RF power density (∼1W and 8.1W), RF conversion efficiency (6 % and 18 %) and much better quantum efficiency (93 % and 91.5 %), respectively for device active-region-widths of 15 μm and 25 μm. Standard Chemical Vapor Deposition (CVD) route has been followed to fabricate the new class of device. Further, the authors have studied the applicability of the newly developed devices for optical-sensing. This comprehensive study reveals that the Device Under Test (DUT) exhibits photo responsivity at least 10 times better than its counter parts. Thus, the study will be useful for future applications in single-photon-detection for defence and civil sectors.

Study of microwave absorption properties of strontium hexaferrite (SrFe12O19) and graphitic‑carbon nitride (g-C3N4) composite in X-band range

To improve microwave absorption in the X-band frequency range (8.2–12.4 GHz), this work describes the creation and characterization of a new composite material made of graphitic carbon nitride (g-C₃N₄) and strontium hexaferrite (SrFe₁₂O₁₉). Easy manufacturing techniques were used to ensure uniformity and the best possible distribution of both components in the composite. Using the vector network analyzer, microwave absorption characteristics were examined, with reflection loss (RL) serving as the primary performance metric. The composite material exhibited remarkable absorption of microwaves, as evidenced by its considerable reflection loss of −59.22 dB at a thickness of 4 mm. It was discovered that the main factor influencing this improved performance was the synergistic interaction between strontium hexaferrite and graphitic carbon nitride.

Geometry Dependent Microwave Absorption Properties in Carbonaceous Materials over X-Band Frequencies (8.2-12.4 GHz) for Stealth Applications

: Carbonaceous materials of two different types, viz. spherical nano carbon black (NCB) powder (Brunauer-Emmett-Teller (BET) surface area ~1400 m2/g) and multiwalled carbon nanotube (MWCNT) (BET surface area ~75 m2/g), have been impregnated in room temperature vulcanized (RTV) silicon rubber matrix to study the effect of geometries of filler particles on microwave absorption characteristics, over X-band frequencies (8.2 -12.4 GHz). The rubber-based composites are prepared by dispersion of NCB and MWCNT fillers in the liquid rubber with loading fractions ranging from 0.3-0.9 wt% and 1.1-1.7 wt%, respectively. The dielectric loss tangent (tanδe) profiles were evaluated for the filler-loaded rubber composites at different concentrations. The calculated Reflection loss (RL) profiles suggest that NCB-based rubber provides maximum RL value, (RL)max ~ -20 dB (99.00 % absorption), at a lower filler concentration of 0.5 wt%, as compared to MWCNT. However, the MWCNT-based rubber composite shows enhanced (RL)min values of ~ -29 dB (~99.99% absorption) due to multiple scattering phenomena. The identified NCB and MWCNT-based rubber-based MW absorbers have potential stealth applications for military aerial vehicles.

Replacing the Gallium Oxide Shell with Conductive Ag: Toward a Printable and Recyclable Composite for Highly Stretchable Electronics, Electromagnetic Shielding, and Thermal Interfaces.

Liquid metal (LM)-based composites hold promise for soft electronics due to their high conductivity and fluidic nature. However, the presence of α-Ga2O3 and GaOOH layers around LM droplets impairs conductivity and performance. We tackle this issue by replacing the oxide layer with conductive silver (Ag) using an ultrasonic-assisted galvanic replacement reaction. The Ag-coated nanoparticles form aggregated, porous microparticles that are mixed with styrene-isoprene-styrene (SIS) polymers, resulting in a digitally printable composite with superior electrical conductivity and electromechanical properties compared to conventional fillers. Adding more LM enhances these properties further. The composite achieves EMI shielding effectiveness (SE) exceeding 75 dB in the X-band frequency range, even at 200% strain, meeting stringent military and medical standards. It is applicable in wireless communications and Bluetooth signal blocking and as a thermal interface material (TIM). Additionally, we highlight its recyclability using a biodegradable solvent, underscoring its eco-friendly potential. This composite represents a significant advancement in stretchable electronics and EMI shielding, with implications for wearable and bioelectronic applications.

Design and experimental investigation of an origami inspired X-band accordion waveguide

This paper presents design, numerical analysis and experimental investigation of an origami inspired X-band accordion waveguide that is aimed to create a flexible and adaptive solutions. The design process is conducted in a Finite Integration Technique (FIT) based microwave simulation software to model and simulate the proposed waveguide, and that shows structural benefits of origami technique based paper folding. Proposed waveguide model is numerically analyzed under both X and Y bending with 30˚, 60˚, 90˚ and 120˚ bending angle to provide its flexibility. Besides, the electric and magnetic field distributions were also obtained and explained in details to provide working mechanism of the proposed accordion waveguide. The S21 transmission characteristics between ports exhibits a decrease of 0.015 dB in numerical results, which is negligible and acceptable in applications. The experimental results demonstrate that the proposed waveguide has effective transmission characteristics within the 8–12 GHz X-band frequency range, with a satisfactory S21 transmission parameter. The numerical and experimental results show that proposed origami inspired accordion waveguide has a huge potential for application in dynamic microwave and satellite components.

Design of compact signal source with reduced phase noise for airborne pulse Doppler RF sensor

Abstract In this article, a low phase noise signal source to be used as local oscillator in pulse Doppler radio frequency (PDRF) sensor is proposed. Innovative design techniques for realization of the low phase noise frequency source using phase-locked loop (PLL) and dielectric resonator (DR) are presented. Qualitative investigations have been carried out on the effect of phase noise in PDRF sensor performance. An X-band vibration resistant PLL-based frequency source with phase noise better than −95 dBc at 1 kHz frequency offset has been designed here. It also presents the design of a 7.6 GHz low phase noise, vibration resistant DR oscillator. Systematic analysis of the key design aspects, their thermal-vibrational stability, and ease of integration with hybrid microwave integrated circuits have been disclosed. A prototype board is fabricated, assembled in a compact mechanical enclosure of dimension 55 × 55 × 15 mm3. Finally, developed module is experimentally validated under 7.6 g rms magnitude random vibration test in three axes and compared results with other state of-the-art similar works. The comparison clearly shows the merit of present research work over other similar existing works.

Valorization of Ricinus communis outer shell biomass to biochar: Impact of thermal decomposition temperature on physicochemical properties and EMI shielding performance

The rising awareness of electromagnetic pollution has increased interest in renewable and ecologically sustainable materials for shielding electromagnetic waves. Research on carbon-based electromagnetic wave absorption materials derived from agro waste is widely explored due to their advantageous characteristics, including low density and consistent physicochemical properties. The research aims to produce biochar with maximum carbon content from Ricinus communis outer shell (RCOS) and to examine the characteristics of biochar/epoxy composites for their application in electromagnetic (EM) shielding. In this study, the composite made from RCOS-based biochar was effectively developed using slow pyrolysis at 400 °C–700 °C. The characterisations of enhanced properties of biochar were conducted by using yield analysis and proximate analysis, elemental analysis, field emission scanning electron microscope (FE-SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction analysis (XRD), thermogravimetric analysis (TGA), electrical conductivity. The biochar pyrolysis results revealed that the biochar yield, fixed carbon and maximum carbon content were 30 wt%, 50.49 wt% and 79.2 wt%, respectively, at 700 °C. Fourier transform infrared (FTIR) spectroscopy revealed that for the biochar at 700 °C, C=C and C-H functional groups were present, and the others were eliminated as volatile gases during biochar production. TG analysis demonstrated higher biochar stability with residues of 75 % for 700 °C. The biochar produced at 700 °C possesses the maximum electrical conductivity of 95 S/m due to the presence of graphitic carbon. The vector network analyser (VNA) measured a maximum shielding efficiency of 26.5 dB in the X-band frequency when adding 40 wt% biochar prepared at 700 °C to the epoxy matrix. The results suggest that the RCOS biochar/epoxy composites have promise as a novel type of absorbent materials because of their low density, lightweight structure, and extensive absorption capacities. These biochar-based lightweight composites can be used as a shielding material for electronic enclosures, telecommunication equipment, and aerospace applications.

Hybrid rib fabric electromagnetic shielding measurement in X-band

This study involves measurement and evaluation of the electromagnetic shielding effectiveness (EMSE) in the X-band frequency range of rib-knitted fabrics formed from hybrid conductors. Hybrid conductive fabrics were made by knitting copper, silver, and stainless steel conductors together with cotton yarn. The basic theory of EMSE is introduced, and the waveguide measurement setup described. The through-reflect-line calibration setup was used to obtain accurate results. After calibration of the established waveguide measurement setup, hybrid conductive fabrics were tested. The measurements were analyzed and the fabrics compared. The aim is to produce a hybrid fabric that is suitable for general use, has a good EMSE, is easy to produce, and offers low-cost high-frequency solutions. An easy-to-produce and low-cost EMSE material is required, especially in new-generation wearable flexible electronic devices and military applications.

Tailoring SrFe12O19 – MoS2 composites for enhanced microwave absorption performance in X-band

The electromagnetic wave-absorbing composites, incorporating strontium hexaferrite and molybdenum disulfide (SrFe12O19-MoS2), are synthesized by mixing in different weight ratios. In the present work, strontium hexaferrite (SrFe12O19) is developed through a low-temperature auto-combustion method while two-dimensional molybdenum disulfide (MoS2) is synthesized by a facile hydrothermal process. The materials and their composites undergo analysis using characterization techniques such as X-ray diffraction (XRD), fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), and vibrating sample magnetometer (VSM) to assess their structural, morphological, and magnetic properties, respectively. The minimal reflection loss (RLmin) of – 47.35 dB is observed at 8.66 GHz for the SrFe12O19-MoS2 (50 %-50 %) composite cast into pellets for microwave absorption analysis in the X-band frequency range. This RLmin is obtained with a sample thickness of 1.7 mm. An adequate bandwidth of 3.1 GHz, representing 77.5 % of the entire X band, is observed for a loss below −10 dB. The synergistic interaction between magnetism and dielectricity makes it an efficient electromagnetic absorber for modern technologies.

A novel engineered sandwich composite with ceramic-coated graphite fibre-reinforced face sheets and an auxetic core for enhanced broadband electromagnetic absorption: design using multiscale computational analysis

Abstract A novel sandwich composite is designed for enhanced broadband absorption using a multiscale computational analysis. The sandwich panel is configured with BaTiO3 coated graphite fiber reinforced polymer (C-GFRP) composite, while BaTiO3 based auxetic material is used as the core material. A computationally efficient in-house tool based on the variational asymptotic method is used to homogenise the electromagnetic properties and evaluate the reflection loss characteristics of the proposed sandwich structure using the scattering matrices. A detailed parametric study of 300 analyses is conducted to identify the optimal sandwich panel configurations for achieving broadband reflection loss under the normal incidence of transverse electric (TE) and transverse magnetic (TM) polarised waves. Two different configurations have been obtained, satisfying the requirements of broadband reflection loss in the X-band frequency range. Configuration (a) Vf = 15% without any ceramic coating, and configuration (b) Vf = 20% with ceramic coating volume fraction (Cf) of 70%. Configuration (a) and (b) maintained the desired reflection loss of greater than -10 dB up to an incidence angle of 40◦ and 60◦, respectively. With the demonstrated capability of covering the entire broadband frequency range, the proposed configurations can serve as baselines to explore novel ceramic-based engineered composite architectures for broadband absorption applications.

Comparison of Microwave Adsorpsion of Core-Shell Fe3O4@SiO2 by Different Methods

Abstract In this research, magnetite nanoparticles coated with sillica from rice husk ash (core-shell Fe3O4@SiO2) were synthesized by a modified stöber method through hydrolisis of silica using basic catalyst. Phase composition, morphology and microstructure were characterized using XRD, SEM, and TEM. The result shows that the sillica shell was successfully coated the core of nanoparticles magnetite. Core-shell Fe3O4@SiO2were synthesized using two method, first silica extraction and second through the silica gel. The application on microwave absorption are measured using VNA at the X-band frequency (8-12 GHz). Materials reach a reflection loss value of -34,29 dB at a frequency of 10,98 GHz for the first method (extraction of silica). For the second method (through silica gel), it exhibits two maximum absorptions with a reflection loss value under -20 dB, which are -23,05 dB at a frequency of 10,1 GHz and -25,03 dB at a frequency of 10,98 dB.

Role of Pb(Zr0.52Ti0.48)O3 on Electric, Dielectric, Electromagnetic Wave Absorption Characteristics of Multiferroic Nanocomposites for Magnetoelectric Devices

Multiferroic composites of ferrite and ferroelcectric phases with systematically varying concentration (100-x)Mg0.48Cu0.12Zn0.4Fe2O4 + x Pb(Zr0.52Ti0.48)O3 (MCZPZT) ( where, x mol% = 0, 20, 40, 50, 60, 80, 100) were prepared by mechanical alloying and sintering methods. The dc resistivity and dielectric constant of the samples as a function of temperature were studied in detail and obtained results are reported. The magnetoelectric effect was investigated for the composites. The sample with 80% ferroelectric phase (MP5), shows largest magnetoelectric output voltage coefficient (dE/dH) H value of 880 μVcm.Oe at 2000 Oe magnetic field. Electromagnetic interference shielding properties of transmission loss and attenuation constant were determined for the composites. Skin depth decreases with frequency from 0.29 to 0.2 cm in the range 8–12 GHz for all composites. The composite MP5 with 80% PZT shows lowest α value between 282 dB m−1 and 414 dB m−1 throughout X-band frequencies. The present results proved that the current magnetoelectric materials of all concentrations exhibit strong magnetoelectric coupling with excellent microwave absorbing performance in X-band region and are appropriate for EMI shielding and novel device applications.