Improved Impedance Matching Research Articles

Design of corrosion-resistant absorbers with a core @ compact film structure based on the “dissolution-redeposition” theory

Chemical stability is the key factor of magnetic metal powder absorbers for their practical applications in the marine environment. Herein, a strategy of phosphating conversion coating (PCC) preparation based on the “dissolution-redeposition” theory which can regulate the surface dissolution reaction and deposition process of metal powder absorber was constructed reasonably. The TA/pH value of the phosphate conversion solution could be adjusted to reduce the hydrogen evolution rate and increase the nucleation rate of CaHPO4 to prepare compact PCC with a certain thickness on the surface of iron powder. Results show that among the different samples, the sample fabricated in TA/pH = 11.37 solution has the best corrosion resistance with the lowest corrosion current density (Icorr = 0.12 μA/cm2) and the highest corrosion potential (Ecorr = -0.453 V) due to the excellent compactness of PCC, and best microwave absorption performance due to the retained conductivity loss and improved impedance matching of the relatively thin thickness of PCC. The minimum reflection loss was -51.31 dB at 16.6 GHz and the effective bandwidth (RL < -10 dB) up to 5.4 GHz with a matching thickness of 2.28 mm. This work provides a useful reference for the design of integrated materials with microwave absorption and corrosion protection for practical applications.

Construction of CoFe2O4/MXene hybrids with plentiful heterointerfaces for high-performance electromagnetic wave absorption through dielectric-magnetic cooperation strategy

Developing high-efficiency electromagnetic wave (EMW) absorption materials is urgently demanded but challenging to tackle the increasingly serious electromagnetic radiation pollution. In this regard, a novel multi-heterostructure hybrid consisting of two-dimensional MXene nanosheets and zero-dimensional CoFe2O4 nanoparticles was successfully constructed by facile solvothermal approach. Benefiting from the improved impedance matching, electric/magnetic coupling effect, polarization loss originated from numerous heterointerfaces and defects, as well as multiple reflection and scattering, the resultant CoFe2O4/MXene (CM) hybrids realize brilliant EMW absorption performance. Notably, the final EMW absorption performance of CM hybrids is closely associated with their electromagnetic parameters, which could be facilely regulated by adjusting the ratios of CoFe2O4 to MXene. The resultant CM hybrids present the optimal minimum reflection loss (RLmin) of −58.8 dB at 9.59 GHz with a tiny thickness of 2.36 mm and exhibit a broad effective absorption bandwidth (EAB) of 6.3 GHz (11.7–18.0 GHz) at a thickness of only 2.03 mm, which covers the whole Ku band. In addition, the effectiveness of CM hybrids as highly efficient EMW absorption materials in real condition is intuitively demonstrated by the radar cross section simulation. This work paves a new route for synthesizing high-performance MXene-based EMW absorption materials with superior practical application value.

Decoupling Method for Four Closely Spaced Planar Inverted-F Antennas Using Parasitic Elements and Bridge Lines

This study proposed a novel decoupling method for four planar inverted-F antennas (PIFAs) operating at 2.0 GHz (f0). The edge-to-edge and center-to-center spacings of the adjacent PIFAs are extremely small (0.05λ0 and 0.17λ0, respectively), resulting in strong mutual coupling among them. In our previous study, we proposed a structure consisting of parasitic elements (PEs) and a bridge line (BL) for the decoupling of two PIFAs. One attractive feature of the proposed method is that no adjustment of the original structure and size of the PIFAs is necessary. However, as the number of PIFAs increases to four, their decoupling becomes considerably more complicated, and impedance mismatch is also an issue to be considered. Therefore, in this study, PEs and BLs are functionally developed to simultaneously achieve low mutual coupling and improved impedance matching of the four PIFAs. The simulated results showed that loading the proposed PEs and BLs onto the four PIFAs could reduce as well as maintain all mutual coupling for less than -10 dB, and simultaneously improve impedance matching. Therefore, the total antenna efficiency at 2.0 GHz could be significantly improved from 64.2% to 84.8% for PIFA1 and PIFA4, and from 35.9% to 74.2% for PIFA2 and PIFA3. Four PIFAs with PEs and BLs were fabricated and measured to validate the simulation results.

Miniaturized broadband upward-folded dipole for base station applications

This paper proposes a compact and broadband dual-polarized base station antenna based on current path extension for 2G/3G/LTE base stations. The antenna is miniaturized by bending the end of the radiator to extend the current path. By bending the antenna, a new resonant mode is introduced to increase the bandwidth. In addition, a parasitic patch is placed above the antenna to improve impedance matching, and the introduction of artificial magnetic conductors reduces the profile of the antenna and significantly improves the radiation characteristics. The antenna radiator has a compact size of only 0.207×0.207λL2 at the lowest frequency with a total profile of 0.136 λL. The measured results indicate that the proposed antenna has a substantial bandwidth of 45.5% and more than 34 dB of high port isolation with a gain of 7.9 ± 0.5 dBi.

Improved impedance matching speed with gradient descent for advanced RF plasma system

Plasma processes are widely used in the fabrication of integrated circuits for the smaller, faster, more powerful circuits demanded by new technology. High-performance semiconductor equipment is required for dynamic random-access memory and three-dimensional NAND flash memory in semiconductor manufacturing. To enhance the speed of RF impedance matching, this paper proposes a method for calculating the load impedance of the plasma chamber. To calculate the target value of the variable components, we employ the input impedance of the impedance-matching unit and the complex impedances of the variable components. In addition, the internal parameters are automatically tuned through the gradient-descent method of machine learning, which improves the accuracy of impedance matching. The new matching method achieved a fast matching time and high efficiency of the matching trajectories. Moreover, it avoids the increase of the reflected power during the matching process, which causes plasma instability, and prohibits significant matching delay in a specific area, which disadvantages the conventional matching algorithm. These advantages are expected to significantly expand the development of new plasma processes from that of conventional impedance matching.

Biomass-derived ferrous magnetic carbon-based nanocomposites from loofah collaterals for excellent electromagnetic wave-absorbing materials

High-performance wave-absorbing materials are always pursuing the goals of thin, lightweight, wide and strong absorption. Hitherto carbonaceous materials are still one kind of the most popular wave-absorbing materials. This work proposed a facile biomass-derivation route to prepare carbonaceous wave-absorbing materials. Loofah collaterals were impregnated with Fe(NO3)3 solution, and a process of iron-catalyzed carbonization for the dried precursors ensued, leading to the formation of Fe@Fe3C/C ternary nanocomposites. It’s found that the Fe@Fe3C/C nanocomposites possessed the absorption abilities from 13.0 to 18.0 GHz with the effective absorbing bandwidth almost covered the Ku band. The superior wave-absorbing properties were mainly ascribed to the synergism of dielectric and magnetic loss mechanisms. Meanwhile, the improved impedance matching and the elevated attenuation ability also favored the strong absorption at specific thickness. This work paved the way for the green synthesis and mass production of high-efficient wave-absorbing materials, and further inspired the regeneration of biomass waste for electromagnetic applications.

Advanced multifunctional IGBT packing materials with enhanced thermal conductivity and electromagnetic wave absorption properties

Insulated-Gate Bipolar Transistors (IGBT) face limitations in high-frequency electronic applications due to heat accumulation and electromagnetic interference issues. To address these challenges, it is crucial to develop packing materials with excellent electromagnetic interference immunity and heat dissipation properties. In this research, a novel epoxy-based packing material (MDCF@C-ZrO2/EP) with high electromagnetic wave absorption and exceptional thermal transport properties was produced by employing a unique three-dimensional carbon structure-induced nanomaterial dispersion strategy. In particular, the three-dimensional MDCF structure effectively prevents packing agglomeration and fosters the formation of an abundant hetero-interface between MDCF and C-ZrO2, leading to improved impedance matching and enhanced electromagnetic wave dissipation capabilities. Remarkably, even at a mere 5 wt% filling level, the material demonstrates an impressive reflection loss value of −58.92 dB and a wide effective absorption bandwidth of 6.68 GHz, effectively covering the entire Ku-band. Additionally, the 3D MDCF@C-ZrO2 significantly enhances the phonon transport path and elevates the thermal conductivity of pure epoxy resin by an impressive ∼ 150%. As a result, this innovative research holds tremendous potential in enabling the application of IGBTs in high-power and high-frequency electronic components, while also contributing to the advancement of next-generation wireless communications and smart devices.

A Review of Nitrogen-Doped Graphene Aerogel in Electromagnetic Wave Absorption.

Graphene aerogels (GAs) possess a remarkable capability to absorb electromagnetic waves (EMWs) due to their favorable dielectric characteristics and unique porous structure. Nevertheless, the introduction of nitrogen atoms into graphene aerogels can result in improved impedance matching. In recent years, nitrogen-doped graphene aerogels (NGAs) have emerged as promising materials, particularly when combined with magnetic metals, magnetic oxides, carbon nanotubes, and polymers, forming innovative composite systems with excellent multi-functional and broadband absorption properties. This paper provides a comprehensive summary of the synthesis methods and the EMW absorption mechanism of NGAs, along with an overview of the absorption properties of nitrogen-doped graphene-based aerogels. Furthermore, this study sheds light on the potential challenges that NGAs may encounter. By highlighting the substantial contribution of NGAs in the field of EMW absorption, this study aims to facilitate the innovative development of NGAs toward achieving broadband absorption, lightweight characteristics, and multifunctionality.

In-situ construction of volcanic rock-like structures in Yb2O3 modified reduced graphene oxide and their boosted electromagnetic wave absorbing properties

Creating porous structures is a practical method for enhancing the impedance matching and interfacial polarization of dielectric materials, which in turn leads to improved electromagnetic (EM) wave absorption performance. However, the use of nanoparticles, nanorods, and two-dimensional materials to construct a simple porous structure typically has a minor effect on the EM parameters and interface polarization. To improve impedance matching and reduce the reflection of EM waves while simultaneously enhancing interfacial polarization, a more rational structure for dielectric materials is desired. Herein, a ytterbium oxide/reduced graphene oxide (Yb2O3/rGO) composite with a volcanic rock-like structure is proposed to exhibit outstanding impedance matching and loss capacity and achieve high EM wave performance. The addition of Yb2O3 is utilized to induce the formation of porous structures with varying morphologies. Yb2O3 not only significantly improves the polarization loss but also facilitates volcanic rock-like structure construction, thus improving the EM wave performance. As a result, the Yb2O3/rGO composites with a volcanic rock-like structure exhibit outstanding EM absorption performance, including three-band absorption (C, X, and Ku bands), as evidenced by their minimum reflection loss (RLmin) of −57.2 dB (equivalent to 99.9999% effective absorption) at 11.6 GHz when the matched thickness is 2.1 mm and an effective absorption bandwidth (EAB) of 4.2 GHz. Simulations in the CST microwave studio further validate the benefits of the composite's unique structure, which shows a radar cross-section (RCS) reduction value of up to 38.1 dB m2. This work offers valuable insights for the development of next-generation EM wave absorption materials through the implementation of a well-designed and distinctive structure.

Electromagnetic Property Modulation of Flaky Ferromagnetic 304 Stainless-Steel Powders for Microwave Absorption at Elevated Temperatures

Soft magnetic metallic absorbents suffer from severe oxidation, reduction in permeability and deterioration in microwave absorption when exposed to high temperatures. In this study, we prepared flaky 304 stainless-steel powders as new microwave absorbents via deformation-induced ferromagnetism. The 304 stainless-steel powders showed significant increases in saturation magnetization (Ms) from 1.03 to 82.46 emu/g when their shape was changed from spheroids to flakes; the Ms further increased to 92.29 emu/g after heat treatment at 500 °C in air. The permeability of 304 alloy powders also showed an obvious increase after ball milling and remained roughly stable after heat treatment at 500 °C in air. Moreover, the permittivity exhibited a sharp decrease after heat treatment, enabling the improvement of impedance matching and microwave absorption. After heat treatment at 500 °C in air for 100 h, the simulated reflection loss of 304 stainless-steel powders with wax still showed attractive levels, giving a minimum value of −22 dB and remaining below −6 dB over 8.5–16.5 GHz at a thickness of 2 mm. Our work can help to include paramagnetic alloy systems as new microwave absorbents for working in harsh environments.

Multiband deformed off-set octagonal patch antenna with improved impedance matching

A novel method is proposed to achieve a single layer miniaturized multiband side-fed microstrip patch antenna for mobile communication applications. Unlike the conventional microstrip antenna with a microstrip line side feed, the integration of a rectangular strip, triangular radiation element, and off-set octagonal radiation patch contributes to the impedance matching, radiation of the multiband signals, and reduction of the length of the regular side-fed antenna. The analysis reveals that a TM01, TM21, and TM22 modes at 1.85, 2.3, and 3.38 GHz, respectively, are excited to realize the multiband radiation. The measurements show that the proposed antenna can work in the 1850/2310/3380 MHz multiple frequency bands simultaneously and can be integrated with planar circuits using a simple structure.

Wideband Circularly Polarized Antenna Array Using Three-Layer Segmented Patches for Q-Band Application

A compact wideband circularly polarized (CP) millimeter-wave (mm-wave) antenna array using three-layer segmented patches (SEP) element is presented in this letter. To achieve miniaturization and wideband feature, three-layer SEP with four <i>L</i>-shaped branches are first designed to generate three CP modes (AR minimum points) within a compact size. With the three CP modes, a broad AR bandwidth of 31.7&#x0025; is achieved by the proposed CP element. Then, four metallic vias and an <i>L</i>-shaped feeding line are used to improve impedance matching. As a result, a wide impedance bandwidth of 33.1&#x0025; is also obtained by the proposed CP element. Based on the proposed wideband CP element, a compact 4&#x00D7;4 CP antenna array fed by a simple full-incorporate microstrip network is designed. Measured results of the array show a 3 dB AR bandwidth of 29.7&#x0025; from 30.1-40.6 GHz, an impedance bandwidth of 36.1&#x0025; from 29.15-42.0 GHz, and a peak gain of 18.2 dBic, which is well suited for Q-band satellite communications.

Improvement of the wave-absorbing properties of biomass-derived porous carbon through in-situ growth of SiC nanowires

SiC nanowire-modified biomass porous carbon materials (GF-SiC) have been developed by uniformly encapsulating SiC nanowires on the surface of porous carbon. GF-SiC exhibits remarkable wave absorption properties of a maximum reflection loss of -60.72 dB at a thickness of 1.74 mm and a wide effective absorption bandwidth (RL≤-10 dB) of 5.52 GHz at a thickness of 2.04 mm. The improved wave-absorbing performance of GF-SiC can be attributed to the three-dimensional porous structure, interfacial polarization effects caused by encapsulated SiC nanowires, and improved impedance matching. This work provides a new idea for the development of low-cost environmental electromagnetic wave absorbing materials.

High-Gain and High-Efficiency Flexible Nonsymmetrical Metamaterial Tag

A flexible nonsymmetrical metamaterial (FNM) tag with high gain, high efficiency and wide readable angle range is proposed here, whose working band is 900MHz-930MHz. We improved impedance match between tag's antenna and chip to reduce the mismatch loss and increase radiation efficient of the tag by loading border cross units with top or bottom defaulted (BCUT/BCUB) units above and below the central folded dipole. Furthermore, the proposed tag is in size of 95mm×57mm×0.23mm, and it can realize 5dBi realized gain and radiation efficient of 89.13%, and 54m reading distance when the reader's effective isotropic radiated power is 42dBm if it's on a plane; and when it is conformal to cylinders whose radius over 26mm, the tag also can work at 900-930MHz, perform over 80% efficient and realize over 35m reading distance in measurement.

Facile hydrothermal process achieving 1T/2H phase tailoring of MoS2 nanosheets for efficient microwave absorption

Electromagnetic pollution is becoming a serious concern. Electromagnetic wave absorbers with light weight, high efficiency and broadband are desirable for electromagnetic protection. Recently, 1T/2H hybrid molybdenum disulfide nanosheets attracted great attention due to the enhanced microwave attenuation driven from fabrication of 1T/2H metal-semiconductor heterojunctions. However, the easy and controllable 1T/2H phase tailoring remains a challenge because of the difficulty in accurately controlling the two-phase ratio and the complicated process. In this study, a facile hydrothermal process is proposed to acquire the 1T/2H MoS2 nanosheets with different 1T contents. The high-resolution TEM images reveal the MoS2 nanosheets are composed of 1T/2H nano-heterojunctions with the 1T and 2H nanodomains arranged alternatively. Without compositing with conductive matters, the MoS2 nanosheets exhibit excellent microwave absorption performance with a maximum reflection loss of −27 dB and an effective absorption bandwidth of ∼4.16 GHz (at 2.3 mm thickness). It benefits from the increased conductivity of the MoS2 nanosheets, abundant 1T/2H phase boundaries and lattice defects, and improved impedance matching induced by the embedding of the 1T phase in the 2H matrix. This work demonstrates the feasibility of the proposed facile hydrothermal process in achieving 1T/2H phase regulation, providing an effective method to tailor the properties of MoS2 nanosheets for various applications.

Double N Stubs for Impedance Matching Improvement of Pogo Pin Test Board at mmWave Applications

Double N Stubs for Impedance Matching Improvement of Pogo Pin Test Board at mmWave Applications

Multi-mechanism response of molten salt-modified MXene with NiCo2O4 nanosheets for enhanced electromagnetic wave absorption performance

To obtain even superior electromagnetic wave (EMW) absorption materials, research is currently focused on composite absorbers. The aim of this work is to prepare composite absorbers with multiple absorption mechanisms using 2D porous Ti3C2Tx MXene as a substrate. Here, porous Ti3C2Tx MXene nanosheets with a large layer spacing were formed through high-temperature molten salt treatment of layered Ti3C2Tx MXene nanosheets. Then, NiCo2O4 nanosheets were anchored onto the porous Ti3C2Tx MXene nanosheets through heat treatment, forming a heterogeneous structure of porous Ti3C2Tx MXene/NiCo2O4 (P-MXene/NiCo2O4). The heterogeneous interface between Ti3C2Tx MXene and NiCo2O4 nanosheets forms strong interfacial polarization, while NiCo2O4 connects the MXene layer to layer forming a conductive network structure. Furthermore, NiCo2O4 nanosheets suppress the self-stacking of porous Ti3C2Tx MXene nanosheets and improve impedance matching. As a result, P-MXene/NiCo2O4 offers excellent EMW absorption performance with a reflection loss (RL) value of − 64.7 dB at a matching thickness of 4.465 mm. This study provides a new idea for pretreating Ti3C2Tx MXene and constructing efficient composite absorbing materials for electromagnetic waves.

Enhancement in the electromagnetic shielding properties of doped [formula omitted] magnetite nanoparticles [formula omitted

Fe3O4 nanoparticles (NPs) are one of the most investigated materials in the field of microwave absorbers. To further optimize the electromagnetic interference (EMI) shielding effectiveness, doped M0.01Fe2.99O4(M=Mn,Ni,Cu,Zn) NPs were synthesized through co-precipitation method. All samples were subjected to X-ray diffraction analysis to determine their crystal structure. Transmission electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy were performed to confirm the morphologies, distribution of elements, and valence of iron in the prepared nanoparticles, respectively. The dielectric and magnetic characteristics displayed a considerable improvement for the doped Fe3O4 samples, except Zn0.01Fe2.99O4 where the obtained values were found to be comparable to those of pure Fe3O4. These variations are described in terms of the homogeneously distributed microstructure, mixed spinel cationic distribution in the doped samples, and Fe2+/Fe3+ ratios at the octahedral interstitial sites. Moreover, the EMI shielding efficiency was measured in the X-band frequency range (8.2 – 12.4 GHz) using a wave guide approach. The total shielding effectiveness of Cu0.01Fe2.99O4 and Ni0.01Fe2.99O4 samples was found to be much higher than that of pure Fe3O4 with absorption being the dominant mechanism. This is most likely owing to their high dielectric permittivity, enhanced conductivity, and high magnetic permeability, which results in improved impedance matching and stronger microwave absorption. This suggests that these doped nanoparticles may be utilized as efficient electromagnetic absorbers.

Influence of elements (Zr, Mo, Cr, Fe, and Ni) doping on the electromagnetic wave absorption performance of Ti3AlC2-based ceramics

Currently, materials that absorb electromagnetic waves (EMW) are being increasingly studied and used. In particular, numerous attempts have been made to improve the performance of EMW-absorbing ceramics, but little attention was paid to the effect of doping on their relevant properties. In this work, Ti3AlC2, a typical MAX-phase ceramic, was doped with different elements (Zr, Mo, Cr, Fe and Ni) at the M site via a pressure-free reactive sintering. Phase and microstructure analysis show that the doped Ti3AlC2 samples possess high purities and typical layered structures. It was noticed that (Ti0.8Zr0.2)3AlC2 demonstrates the lowest reflection loss (−48.0 dB at the thickness of 1.62 mm) and a maximum effective absorption bandwidth of 3.9 GHz. Elemental doping has been proved to alter the dielectric and magnetic properties of Ti3AlC2, and the boosted EMW absorption performance was found to be originated from the improved impedance matching. Here, we systematically investigated the influence of different dopants on the EMW absorption characteristics of Ti3AlC2, which provides significant insights for the future design of novel EMW-absorbing materials.

An Adaptive Broadband Active Impedance Matching Network for Underwater Electroacoustic Transduction System

Since the power supply is limited in ships, the impedance matching network is essential for a high-power underwater electroacoustic transduction system. However, the existing impedance matching networks can barely achieve full impedance matching under a wide frequency change range. This paper proposes a shunt active impedance matching network (SAIMN) to achieve adaptive broadband impedance matching (up to 400Hz) for increasing power utilization from a power amplifier to the transducer. Firstly, the load impedance characteristic and operation principle of SAIMN are introduced mathematically. Secondly, the parameter design method is provided to improve impedance matching performance. After that, a compound control strategy is presented to control the power amplifier and proposed SAIMN. Finally, the simulation and experimental results validate the effectiveness of the proposed SAIMN and its control strategy. The results clearly show that the proposed SAIMN can adaptively match load impedance for the different loads in a broadband frequency range. The power factor of the power amplifier is significantly improved, and the current stress of the switching device is significantly reduced with the proposed SAIMN.