Improved Impedance Matching Research Articles

Compositional design of C-coated multi-elemental alloy nanoparticles for superior microwave absorption

Exploring improved electromagnetic wave absorption performance in magnetic components involves capitalizing on dual dielectric relaxation and multiple magnetic resonances, ultimately giving rise to a dielectric-magnetic matching effect. Herein, a one-step Metal-organic Chemical Vapor Deposition (MOCVD) method has been utilized to fabricate C-coated ternary and quaternary alloy nanoparticles (FeCoNi, FeCoNiCu, FeCoNiMg, and FeCoNiMn) with tunable magnetization. The results affirm that the capabilities of impedance matching and electromagnetic wave attenuation can be significantly regulated by compositing nanoparticles with different elements. The optimized C-coated FeCoNiMg nanoparticles demonstrate an exceptional capacity for electromagnetic wave attenuation, achieving a reflection loss value of −51.8 dB at a matched thickness of 2.9 mm. Moreover, the absorption bandwidth significantly broadens to 7.60 GHz (10.4 – 18.0 GHz) with a thickness of 2.7 mm. The exceptional performance in electromagnetic attenuation is credited to the dielectric loss and improved impedance matching characteristics induced by the C-coated FeCoNiMg nanoparticles. The findings from this study will be beneficial in the development of lightweight and highly effective electromagnetic wave absorbers using magnetic alloy nanoparticles.

Ti3C2Tx/PANI/CoNi as a ternary composite material unveiling excellent microwave absorption performance

Ti3C2Tx MXene material exhibits exceptional dielectric properties and a distinct layered structure, making it a noteworthy microwave absorbing material. However, its microwave absorption performance is limited due to poor impedance matching and a single loss mechanism. To address these issues, this work develops a solvothermal method to introduce the magnetic component CoNi alloy and generate organic polymer PANI through in-situ polymerization, resulting in the preparation of Ti3C2Tx/PANI/CoNi ternary composites that significantly improve impedance matching and microwave absorption performance. The microwave absorption properties of the binary and ternary composites are compared, and the superior performance of the ternary composites is emphasized. Among the ternary composites, M-P-CN 3:1:8 exhibited an excellent microwave absorption performance, demonstrating a minimum RL value of −55.48 dB and an effective absorption bandwidth of 5.1 GHz at a thickness of 2.0 mm. The synergistic effect of multiple loss mechanisms, multilayer structures, and multiple interfacial polarization methods further contribute to the enhanced microwave absorption performance of ternary composites. This study provides a straightforward method for synthesizing and designing multi-component composite absorbing materials based on MXene.

Facile synthesis and magneto-alignment effect on the microwave absorption property of NiCo2O4/NiO/Co3O4 composites

A simple method of high-temperature ignition to metalorganics was successfully used to synthesise composites of NiCo2O4, NiO and Co3O4. A detailed investigation of the composite’s microwave absorption properties revealed the magneto-alignment effect. By closely arranging NiCo2O4, NiO and Co3O4 nano-particles in epoxy resin, the magnetic exchange is strengthened under the influence of a magnetic field. The sample without magnetic alignment, S0, exhibited poor absorption efficiency with reflection loss (RL) values hardly reaching − 10 dB across a frequency range of fixed and different thicknesses (2–18 GHz). In comparison, the oriented composite exhibited higher permittivity and permeability, particularly in the high-frequency range. Considering the improved impedance matching and reasonable adjustment of dielectric and magnetic losses, the microwave absorbing performance of the oriented composite substantially improved in the 10–14 GHz range. The minimum RL is reduced to − 45.11 dB with an effective bandwidth of 4 GHz. Herein, we present a straightforward method to increase the microwave absorption performance of NiCo2O4 by modifying the macroscopic order and degree.

Broadband microwave absorption for thin FeSiCr/rGO composites

A series of FeSiCr/reduced graphene oxide composites (FeSiCr/rGO) are successfully prepared by ball milling as a lightweight broadband electromagnetic wave absorbers. The microstructure and absorption properties of the FeSiCr and FeSiCr/rGO composites were compared in detail. The results show that the milled FeSiCr/rGO composite for 1 h can achieve a minimum reflection loss (RLmin) of −15.2 dB at 3.64 GHz with the thickness of 2.0 mm. Whereas, at the thickness of 1 mm, the effective bandwidth is 9.8 GHz when the value of the RL below −5dB. The FeSiCr/rGO composites show better microwave absorption thanks to the improved impedance matching. Furthermore, the peak of RL for FeSiCr/rGO composites, is entirely within the C-band and Ku-band, with a thickness ranging from 1 mm to 2 mm. Overall, this thin and lightweight FeSiCr/rGO composites can meet the requirement of strong and broadband absorber.

10–14GHz and 14–18GHz Interdigital Planar Bandpass Filters for Frequency Multiplexer

This paper presents the design of two wideband bandpass filters (BPF) operating in the 10–14 GHz and 14–18 GHz ranges for a five port 1-18GHz frequency multiplexer. The 10–14 GHz BPF utilises an interdigital array of resonators with asymmetrical widths and is combined with a low-pass filter for wide stopband characteristics. Sharp attenuation in the stop bands is achieved by including quarter wavelength open stubs. The 14–18 GHz BPF incorporates three interdigital resonators with a modified middle resonator, introducing a variable gap width for improved impedance matching. Open-circuited stubs and a bandstop filter further enhance attenuation in the stop bands. Equivalent circuit models accompany both filters. Both filters exhibit excellent performance, as evidenced by the reflection coefficients below −12 dB within their respective frequency ranges. The insertion loss remains below 2.5 dB throughout the passband, indicating efficient signal transmission. Moreover, the group delay for both filters is less than 0.8 ns, indicating minimal signal delay. These results demonstrate the high-quality characteristics of the designed filters, making them suitable for a wide range of applications requiring efficient signal filtering and multiplexing.

Lightweight multi-dimensional MXene/Ni chain/porous carbon with the improved impedance matching for high-performance microwave absorption

Dielectric/magnetic coupling is an effective method to improve the electromagnetic (EM) absorption characteristics of wave-absorbing materials. In addition, the design of the porous structure meets the requirements of light weight of absorbing materials. In this work, Ti3C2Tx (MXene) nanosheets and Ni chains are filled into porous carbon obtained by carbonization of melamine foam to obtain MXene/Ni chain/Melamine foam-derived porous carbon (MFPC) composites with low density, high conductivity and excellent EM absorption performance. Surprisingly, the minimum reflection loss of the MFPC/M-3 reached -41.55 dB at 2.3 mm, and its effective absorption bandwidth (EAB) was 5.15 GHz. The MFPC/M-4 has the widest EAB of 5.68 GHz at 2.3 mm. High EM wave absorption performance is attributed to the dielectric/magnetic coupling, which improves the impedance matching characteristics and provides multiple scattering, interfacial polarization, conductivity loss, dipole polarization, and magnetic loss. Furthermore, composites also have lower density and higher electrical conductivity. This dielectric/magnetic coupled porous composite will have good development in the field of EM absorption.

Ni/Porous Carbon-Based Composite Derived from Poplar Wood with Ultrabroad Band Microwave Absorption Performance

Electromagnetic wave (EMW) absorbers and electromagnetic shielding materials have attracted much attention in recent years. In this paper, Ni/wood-based porous carbon (WPC) composite material was prepared via morphology genetic method by using nickel chloride and poplar as raw material, The experimental results show that the microwave absorbing properties of the materials are related to the pyrolysis temperature, when the pyrolysis temperature settle at 700 °C, the minimum reflection loss of WPC-Ni can reach-60.4 dB with the thickness of 2.93 mm. Moreover, the effective absorption bandwidth has been greatly broadened up to 7.3 GHz when the thickness is 2.63 mm. The reason for such excellent wave absorbing performance is that the introduction of magnetic particles Ni and WPC-Ni regular straight channels improve impedance matching, the heterogeneous interface of Ni/ wood increases the polarization loss of electromagnetic waves. It is believed that this work can provide a new idea for the preparation of low-cost and high-efficiency broadband microwave absorber.

Additive manufacturing of broadband electromagnetic wave absorbing materials: Polymer-derived SiC/Si3N4 composites with triply periodic minimal surface meta-structure

High temperature ceramic-based electromagnetic wave (EMW) absorbing materials has been widely studied as multifunctional materials for the application in various high-speed vehicle. However, current high temperature EMW absorbing materials are limited by narrow absorption bandwidths due to their inferior impedance matching characteristics across a wide frequency range. This study proposes a novel polymer-derived SiC (PDCs-SiC)/Si3N4 triple periodic minimal surface (TPMS) meta-structure inspired by the gyroid bionic structure. The presented design strategy integrates the material and meta-structure properties, which was inspired by the interaction mechanism between these properties on the EMW absorption performance of the prepared composites. The TPMS meta-structure were fabricated through three-dimensional (3D) printing combined with precursor infiltration pyrolysis technology, followed by annealing treatment and Al(H2PO4)3 sol infiltration. The results demonstrated that the dielectric constants of the composites were reduced through annealing treatment and Al(H2PO4)3 sol infiltration process, thereby improving impedance matching and enhancing the EMW absorption performance. The effective absorption bandwidth (EAB) of the prepared PDCs-SiC/Si3N4 composites reached 3.52 GHz at a thickness of 3.3 mm. Furthermore, TPMS meta-structure with DSM unit demonstrated the excellent absorbing properties with a wide absorption bandwidth of 11.12 GHz, as evidenced by simulations and experiments. This can be attributed that the fully connected porous TPMS meta-structure further improved the impedance matching and enhanced the transmission path of electromagnetic waves, while the discontinuous unit in the top layer of DSM induced electromagnetic wave resonance and interference cancellation, thereby enhancing the EMW absorption performance of composites. This study presents an innovative development strategy for designing and preparing high-temperature electromagnetic wave absorbing materials with broad bandwidth.

Decoration of conjugated polyacene quinone radical (PAQR) with Fe3O4 nanospheres achieving improved impedance matching and electromagnetic wave absorption

Conjugated polymers have exhibited great potential to reform traditional electromagnetic wave absorbers owing to their advantages in tailorable electrical properties, lightweight, good processability, high environment resistance, and so on. In this work, conjugated polymer of polyacene quinone radical (PAQR) with unique nomadic polarization behavior was prepared by a solid-state polymerization process and subsequently decorated with Fe3O4 nanospheres through a solvothermal method to obtain PAQR/Fe3O4 nanocomposites. Electromagnetic wave absorbing properties of the polymer-based nanocomposites were thoroughly discussed. It was found that PAQR decorated with Fe3O4 in moderation exhibited excellent wave absorbing abilities with absorbing bandwidth of 4.8 GHz and reflection loss exceeding - 40 dB at a thin thickness around only 1.5 mm. The wave absorbing mechanisms were not only attributed to polarization loss and conduction loss of conjugated macromolecules, but also related to that the decoration of Fe3O4 significantly improved the magnetic loss abilities and impedance matching for the nanocomposites. This work firstly studied the electromagnetic properties of PAQR-based composites in GHz bands and proposed a powerful support for the development of conjugated polymer wave absorbing materials.

Applying Characteristic Impedance Compensation Cut-Outs to Full Radio Frequency Chains in Multi-Layer Printed Circuit Board Designs.

Modern wireless communication systems are of utmost importance to various sectors such as healthcare, education, the household, and the advancement of emerging technologies like the internet of things, autonomous vehicles, and the enhancement of 5G. Further development and improvement of these systems drives the need for small dimension, high integration and density, and cost-effective electronic devices. Achieving optimal performance in wireless electronic devices involves overcoming engineering challenges related to microstrip line signal integrity. This research addresses the impact of surface mount technology (SMT) component pads on signal integrity, proposing a novel high-frequency microstrip line structure for mitigating impedance discontinuities. The study introduces stepped microstrip lines and explores characteristic impedance compensation techniques. A six-layer printed circuit board (PCB) structure is presented, and the effects of compensation on signal integrity are analyzed using time-domain reflectometry and scattering parameter measurements. The results demonstrate the effectiveness of compensation methods in aligning characteristic impedance with desired values, thereby ensuring improved impedance matching and transmission coefficients. The average over-the-length impedance for the proposed structure with compensation applied was measured to be 52.7 Ω, which is only 1.3 Ω (2.5%) more than that of the reference microstrip. Applying reference plane cut-outs leads to a maximum compensated absolute value of more than 30 Ω to reach the target impedance with a 10% tolerance. This research contributes valuable insights for advancing wireless communication systems and maintaining robustness in high-frequency microstrip transmission lines.

Multi-level hollow sphere rich in heterojunctions with dual function: Efficient microwave absorption and antiseptic

Effective electromagnetic wave absorption is now possible thanks to the design of the dielectric-magnetic double loss mechanism and the rich heterogeneous structure. In this study, hollow carbon spheres with rich heterostructures were synthesized using an easy and effective in situ growing approach. In addition to improving impedance matching, the hollow structure also reduces material density and weight. By modifying the load, this system can alter the dielectric characteristics of MXene, which in turn affects the sample's ability to absorb electromagnetic waves. MXene and the carbon material create a thick conductive network during the whole electromagnetic wave absorption process, creating the ideal environment for conduction loss. The sample's ability to attenuate electromagnetic waves is further improved by the interfacial polarization that the rich heterogeneous structure can produce. Co-magnetic nanoparticle nanoparticles are the main source of magnetic loss. The MXene@Co/C-100–800 (MCC-100–800) exhibits excellent electromagnetic wave absorption performance under the synergy of multiple loss mechanisms, with the maximum effective absorption bandwidth (EABmax) reaching 7.20 GHz and the minimum reflection loss (RLmin) being –53.99 dB at 2.10 mm. Finally, this work is guided by the coating engineering of MXene and provides new ideas for the rational design of heterostructures of nanomaterials.

Construction of ZnO/Ni@C hollow microspheres as efficient electromagnetic wave absorbers with thin thickness and broad bandwidth

Ingenious microstructure design and rational composition collocation have been proved to be an effective strategy for developing efficient electromagnetic wave (EMW) absorbers. It would be promising to fabricate a hollow structured composite integrating multiple loss mechanisms (conduction, magnetic, and polarization losses) for excellent EMW absorption. Herein, a novel dielectric-magnetic compound of ZnO/Ni@C hollow microsphere was prepared through hydrothermal reactions followed by an in-situ chemical vapor deposition (CVD). In this ternary composite, abundant ZnO/Ni heterostructures formed the hollow microsphere skeletons and provided unique Schottky junctions, which endowed the composite with improved impedance matching and strong polarization loss. Meanwhile, the amorphous-polycrystalline carbon layer deposited on the surface of each microsphere enhanced the conduction and interfacial polarization losses. In addition, the magnetic Ni nanoparticles induced magnetic loss. Benefiting from the synergistic effect of the hollow structure and multiple loss mechanisms, the ternary composite exhibits an effective absorption bandwidth as wide as 6.55 GHz at a thickness of only 1.85 mm, accompanied by a minimum reflection loss of –39.8 dB. Besides, the radar cross-section and the electromagnetic field simulation further verify the superior EMW absorption performance of the composites. Our work provides a new reference for the fabrication of dielectric-magnetic ternary hollow microspheres as EMW absorbers with thin thickness and broad bandwidth.

Microstructure regulation and microwave absorption properties of ZnO/RGO composites.

Electromagnetic waves can cause different degrees of damage to the human body. People are developing unique nanomaterials with excellent reflection loss (RL), thin thickness, wide frequency band and light weight to improve the absorption efficiency of electromagnetic waves. Using a hydrothermal method, ZnO nanocrystals are combined with graphene oxide (GO). After heat treatment, evenly dispersed ZnO nanocrystals are attached to the GO surface or inserted into the lamellae, and the amount of Zn(CH3COO)2·2H2O and GO is selected to obtain ZnO/RGO nanocomposites with different mass ratios (1 : 1, 1 : 2, 1 : 3). The ZnO/RGO nanocomposites were mixed with paraffin wax with different mass ratios (15, 20, 25, 30 wt%) to explore their electromagnetic parameters and wave absorption properties. It is found that at 25 wt%, ZnO : GO = 3 : 1 and thickness of 3 mm, the sample exhibits excellent wave absorption performance (-36.6 dB) and wide effective absorption bandwidth (6.6 GHz). The microwave absorption performance is enhanced because ZnO nanocrystals inhibit RGO agglomeration and improve impedance matching between the heterostructure interface and RGO.

Electrospun Co/attapulgite/carbon nanofibers with the curved and multicomponent heterogeneous structures as excellent microwave absorbers

Multicomponent design based on magnetic carbon nanofibers (CNFs) composite is an expected approach to achieve excellent microwave absorption. Herein, the Co/attapulgite (ATP)/CNFs were prepared via electrospinning and vacuum calcination. The structure and electromagnetic (EM) properties of Co/ATP/CNFs impacted by the structure evolution of ATP at different calcination temperatures was investigated. At the calcination temperature of 550 °C, the optimal reflection loss (RL) reached −46.67 dB at 15.76 GHz in 2.5 mm thickness, and the effective absorbing bandwidth (EAB) reached 6.72 GHz at 3.0 mm thickness. ATP is introduced into Co/CNFs to construct the magnetic CNFs with various interfaces and bending structures, thereby enhancing dielectric loss and improving impedance matching, and finally realizing broadband absorption. This work presents a promising mentality to obtain environmental protection and efficient microwave absorbing materials (MAs).

A Compact RF Energy Harvesting System With an Improved Impedance Matching Network

A Compact RF Energy Harvesting System With an Improved Impedance Matching Network

Strong and wide microwave absorption of multilayered metastructure enhanced by impedance matching mechanism

The present study proposes a strong and wide microwave absorption of multilayered metastructure (SWMAMM) capable of achieving an ultra-wideband absorption of −20 dB and 60° oblique incidence. SWMAMM primarily consists of metasurface-Ⅰ (MS-Ⅰ), metasurface-Ⅱ (MS-Ⅱ), and a top absorption-enhanced skin, which are separated by three support dielectric slabs. Based on impedance matching theory and the interference model, MS-Ⅰ serves as the core functional layer for wideband absorption; whereas MS-Ⅱ not only provides ultra-wideband impedance matching but also enhances absorptivity, distinguishing it from most designs. To further improve impedance matching, different hole arrays are incorporated into the substrates of MS-Ⅰ, MS-Ⅱ, and the top absorption-enhanced skin by modifying their equivalent reactance. The measurement results demonstrate that the −10 dB and −20 dB reflection bands are separately in the range of 3.97–23.19 GHz and 5.24–21.81 GHz when the oblique incidence angle reaches 5°; the −10 dB reflection band can cover the range of 5.99–25.00 GHz when the oblique incidence angle reaches 60°. Our approach, which involves impedance matching design of MS-Ⅱ and optimizing impedance matching by incorporating different hole arrays into the substrates of the MS-Ⅰ, MS-Ⅱ, and the top absorption-enhanced skin, can be applied to various unit cells and dielectric materials. This approach offers significantly enhanced convenience and efficiency compared to existing designs, thereby facilitating further optimization and development of Electromagnetic absorbers.

Hierarchical porous carbon fibers for broadband and tunable high-performance microwave absorption

Constructing multiple polarization losses and improving impedance matching in carbon materials is essential for improving electromagnetic wave absorption performance of carbon materials. Meanwhile, surface contamination of electromagnetic wave absorbers has a significant impact on their absorption performance. Herein, a pod-like macroporous carbon nanofibers with self-cleaning function are successfully prepared by Electrospinning-etching strategy. Through the adjustment of SiO2 and pore structure, conduction loss, dipole polarization loss, interface polarization loss, and impedance matching of carbon nanofibers are optimized simultaneously. The optimized a pod-like macroporous carbon nanofibers has strong absorption and wide effective absorption bandwidth. With a cavity content of 4 %, the minimum reflection loss at 2.29 mm is -49.36 dB, and the effective absorption bandwidth is 7.6 GHz and the matched thickness is 2.16 mm. This result indicates that cavity and pod-like structure can significantly improve dielectric properties and enhance interface polarization loss and conductivity loss. The simulation results verify that the pod structure has a greater impact on surface electric field distribution, which shows that interface polarization is caused by the cavity structure. In addition, the contact angle of absorber is 105 °, which proves its self-cleaning ability. This functional absorbing material has potential to meet future practical applications.

Regulating N-doping strategies to construct 3D interconnected abundant porous N-doped carbon for polarization loss-enhanced microwave absorbers: Theory, design, and experiments

The widespread proliferation of modern portable electronic devices has necessitated the development of functional materials with high-efficiency microwave absorption properties. In this study, we utilized biomass-derived jujube shells as a carbon source and employed a nitrogen-doping process to modify carbon materials, resulting in the fabrication of outstanding microwave-absorbing biomass-based nitrogen-doped porous carbon. Additionally, we discussed the influence of different nitrogen sources on material structure and microwave absorption performance. These N-doped porous carbon materials exhibited excellent specific surface areas, particularly Org-N, which facilitated the formation of conductive networks and the multi-stage reflection and scattering of microwave. Moreover, N-doping created numerous defect sites and heterogeneous structures, improving impedance matching, thus promoting dipole polarization and interface polarization effects, which accelerated electron migration and interlayer hopping, contributing to the attenuation of microwave energy. The lowest reflection loss for Org-N, Inorg-N, and Mixed-N reached −27.3 dB, −40.9 dB, and −45.6 dB, respectively. Mixed-N exhibited optimal microwave absorption performance at 9.9 GHz with d = 2.4 mm and achieved an effective absorption bandwidth (EAB10) of 3.0 GHz (11.0 GHz–14.0 GHz) at d = 2.0 mm. Additionally, the enhancement of polarization relaxation effects was elucidated by examining the charge density distribution in molecular models featuring various N-doping forms. Consequently, biomass-derived N-doped porous carbon materials emerge as lightweight and highly efficient functional materials for microwave absorption purposes.

Well-matched PANI@FePO4@FeSi hybrid composite with excellent microwave absorption property

PANI@FePO4@FeSi composites were prepared by one-pot synthesis. The PANI@FePO4 coating layer can effectively enhance magnetic loss, dielectric losses, and improve impedance matching by reduce the skin effect. The optimized reflection loss (RL) of the composites is −54 dB at 15.76 GHz with the absorption bandwidth (RL<−10 dB) of 2.7 GHz (14.3−17 GHz).Density functional theory (DFT) and ANSYS High-Frequency Structure Simulator (HFSS) analysis results suggest that destruction of local microstructural symmetry and inducing additional electric dipoles at the interface of each component. The density of state (DOS) of p orbital near the Fermi level decreases. Thus, dipole oscillation and polarization loss get enhanced under the external electromagnetic field. This work provides an avenue for designing new microwave absorbers.

Utilizing Se vacancies as electronic traps to synergize impedance matching and dipole polarization with ultrathin strategy to boost Fe-Se electromagnetic wave absorption

The electronic structure, transport properties and magnetic properties of the material can be adjusted by regulating the formation and concentration of anionic vacancies. In particular, materials based on transition metal chulides (TMC) have high second-order nonlinearity and atomic thin thickness, and anionic vacancy engineering can effectively achieve the optimization of material properties. However, the impact of anion vacancy engineering on dipole polarization has not been fully resolved and clarified yet, and it cannot be solely relied upon semi-empirical methods. Therefore, it is of utmost importance to deeply understand the intrinsic mechanism between vacancies and electromagnetic (EM) parameters. This knowledge will provide crucial guidance for the development of advanced electromagnetic wave (EMW) absorption materials. In this study, a novel approach is proposed for the first time, which involves the creation of Se vacancies at the heterogeneous interface formed by Fe-Se compounds. Remarkably, the generation of Se vacancies leads to an increased electron transfer from Fe to Se atoms, resulting in the formation of numerous dipolarization centers. This effect significantly enhances the material’s polarization loss capacity. Furthermore, the presence of Se vacancies acts as traps for nearby free electrons, reducing the material’s conductivity, weakening the skin effect, and improving impedance matching. The precise modulation of Se vacancies in Fe-Se compounds has led to the achievement of ultrathin characteristics and significantly enhanced EM absorption capabilities. With a thickness of only 1.5 mm, the effective absorption bandwidth (EAB) reaches 5.42 GHz, covering the Ku band, which represents a remarkable increase of 53.5 % compared to unmodified Fe-Se compounds. At a thickness of 1.3 mm, the minimum reflection loss (RL) reaches −42.4 dB, demonstrating an impressive improvement of 41.3 %. Moreover, simulations of the radar cross section (RCS) indicate that the material possesses a robust microwave attenuation ability, underscoring its great potential for practical applications.