Transmission Of Electromagnetic Waves Research Articles

Design and manufacturing of waveguide of parabolic antenna using EDM process

Wireless technology was one of the main areas of research in the world of communication system today and a study of communication incomplete without an understanding of the operation and manufacturing of waveguide of parabolic antenna. Waveguide is an important electromagnetic wave transmission Component of parabolic antenna. potential benefits of parabolic antenna doesn’t required any cables to transmitte electromagnetic signal. Designing of waveguide was a most important role before its manufacturing. An attempt is made to design and manufacture the waveguide by varying cross- section using CREO software. Manufacturing of waveguide Carried out by milling, the inner pocket of waveguide was machined by Electrical discharge machining process. Which results accurate surface and suitable for travelling of electromagnetic wave without any disturbance.

Wave-transparent electrothermal composite film for anti-icing/de-icing

Wave-transparent materials are essential to ensure the high-fidelity transmission of electromagnetic waves and to safeguard antenna systems in critical fields such as aerospace, transportation, and communication. However, surface icing of wave-transparent materials or antennas will severely impact their transmission and aerodynamic performance. In this study, a patterned electrothermal composite film (PEF) was prepared and optimized by relevant theories of electromagnetic leakage and frequency selective surface. The PEF demonstrated excellent rapid heating and stability, requiring only 0.4 W/cm2 power density to completely anti-ice in dynamic icing experiments. Additionally, the PEF boasted high transmittance, exceeding 80 % across an ultra-broadband range of 2–18 GHz. Furthermore, the PEF was lightweight and could be prepared in a large area. The results suggest that the PEF has the potential for valuable applications in radar radomes, wave-transmitting walls, and protective walls, particularly in cold areas.

A generalized temporal transfer matrix method and its application to modeling electromagnetic waves in time-varying chiral media

Chiral metamaterials have attracted significant attention in recent years due to their unique properties in both the microwave and optics regimes. However, most existing works rely on engineering the desired properties of spatial interfaces, and the concept of time-varying chirality has only recently begun to be explored. As a consequence, there is currently a lack of suitable tools for evaluating the propagation of electromagnetic (EM) waves in time-varying chiral media. As such, this paper presents the theoretical formulation for temporal reflection and transmission of EM waves in time-varying chiral media using the temporal transfer matrix method (TTMM). The developed TTMM tool will then be utilized to explore several application examples including a structure with an arbitrary temporal profile, optical activity generated from time interfaces, and anti-reflection temporal coatings. In addition, we employ a specialized finite-difference time-domain (FDTD) technique, known as BI-FDTD, in all the scenarios to validate the proposed theory.

Biomimetic thermally responsive photonic crystals film with highly robust by introducing thermochromic dyes

Thermally responsive photonic crystals (TRPCs) are intelligent responsive materials that can dynamically coordinate electromagnetic wave transmission, translating thermal stimuli into optical signals and structural color changes. However, it remains a big challenge to develop a robust TRPC, because of the thermochromic mechanism of unstable dramatic volume change that collapses photonic crystal (PC) structure. We demonstrate a highly robust and flexible TRPC film inspired by the chameleon, combining thermochromic dyes (TDs) with PC for a synergistic response. There is only negligible color fluctuation even after 2000 color-change cycles, attributing to no lattice parameter change during the thermal stimulus. Moreover, both positive (transparency to opaque color) and negative (opaque color to transparency) TDs are introduced into TRPC, implementing a full-color RGB thermally-responsive system. The response of the positive-TRPC and negative-TRPC temperatures were 32.0 and 50.5 °C, respectively. A TRPC film with environmental adaptability was designed, which offers a promising route to anti-counterfeiting, steganography and smart window.

Full-parameter omnidirectional transformation optical devices.

Transformation optics (TO) provides an unprecedented technique to control electromagnetic (EM) waves by engineering the constitutive parameters of the surrounding medium through a proper spatial transformation. In general, ideal transformation optical devices require simultaneous electric and magnetic responses along all three dimensions. To ease the practical implementation, previous studies usually made use of reduced parameters or other simplified approaches, which inevitably introduce extra reflection or unwanted phase shift. Up to today, experimental realizations of full-parameter transformation optical devices in free space are still quite limited. Here, a general design strategy is proposed to solve this problem. As a specific example, a full-parameter spatial-compression TO medium with constitutive parameters taking the diagonal form diag(a, a, 1/a) for the TM wave incidence was designed and realized experimentally. Such spatial-compression TO media were then applied to the implementation of an ideal omnidirectional invisibility cloak capable of concealing a large-scale object over a wide range of illumination angles. Both the simulation and experiment confirm that the cloak allows for nearly unity transmission of EM waves in the forward direction without introducing extra scattering or phase shift. This work constitutes an important stepping stone for future practical implementation of arbitrary full-parameter omnidirectional transformation optical devices.

Well‐posedness and Mittag–Leffler stability for a nonlinear fractional telegraph problem

AbstractThe ordinary diffusion models in continuous media are derived from basic principles: Conservation of energy and momentum. The classical telegraph equation is one of the earliest and most commonly used equation to describe the transmission of electromagnetic waves. In fractal and disordered media, to capture the complex diffusion feature, we consider rather fractional models. Indeed, the mean square displacement in anomalous media is no longer proportional to the time but rather proportional to a power of time whose exponent may be between zero and one or between one and two. This is the case for the present fractional telegraph equation in the presence of non‐negligible voltage wave. Here, the well‐posedness and stability of a telegraph problem with two time‐fractional derivatives is discussed. In addition to being a noninteger problem, the equation in the model is subject to a nonlinear source as well as a nonlinear lower order fractional derivative term. First, the well‐posedness in an appropriate underlying space is established by the use of resolvent operators. Then, it is proved that, despite the presence of these nonlinearities, solutions are Mittag–Leffler stable. This confirms (and extends) the fact that the lower order term plays the role of a damper in the fractional case. To this end, we combine the energy method with some properties of the Caputo fractional derivative.

Anisotropic Shape Memory Composite for Dynamically Adjustable Electromagnetic Interference Shielding

Smart electromagnetic interference (EMI) shielding materials that enable dynamical adjustment of electromagnetic wave transmission are highly desirable for various applications. Nevertheless, ordinary materials show nonadjustable EMI shielding performance after deployment. Herein, an anisotropic smart EMI shielding composite is presented, which shows tunable EMI shielding effectiveness by rotation, shape memory, and simple stacking. The composite possesses a sandwich structure consisting of two graphene fibrous films (GFFs) with intermediate shape memory poly(ethylene-co-vinyl acetate) (EVA). Owing to the aligned graphene fibers of GFF, the GFF/EVA composite showed anisotropic mechanical property, shape memory property, and shielding effectiveness. The composite shows high tensile strength but declined shape memory property in the axial direction (0°) of the graphene fibers. In the 0° direction of the GFF/EVA composite, a total shielding effectiveness (SET) of >40.8 dB in the X-band is observed, which is much higher than that in the 90° direction (vertical, <8.1 dB). The rotation-modulated EMI shielding of GFF/EVA is achieved by the anisotropy-dependent EMI shielding performance. Moreover, tunable EMI shielding is demonstrated through the shape memory process of the composite and the average SET can be adjusted in the range from 43.2 to 33.1 dB by fixing a tensile strain from 0 to 100%. Furthermore, the EMI shielding of the multilayered composite can be modulated by stacking individual GFF/EVA composites at different angles. The smart GFF/EVA composite with tunable and function-switchable features is demonstrated, which will contribute to the development of smart EMI shielding materials and devices for electromagnetic applications in various fields.

Smart Wood Dual‐Action Off/On Versatile Switches Based On Highly Sensitive Electrical And Electromagnetic Mechanosensing Performances

AbstractSmart electromagnetic (EM) functional materials that can arbitrarily utilize EM energy and reduce EM pollution are attractive for future EM devices in an information society; however, studies on precise EM interference (EMI) shielding and sensing are rare. In this work, dual‐action electrical and EM‐responsive mechanoreceptors are prepared from electrically conductive polypyrrole (PPy) nanoparticle (NP)‐infiltrated anisotropic wood (PW) aerogels. The prepared PW aerogels are composed of curved stacked layers of aligned cellulose nanofibers, and can be reversibly condensed and reconstructed for conductive network control during cyclic compression. These PW aerogels can withstand up to 74% compressive strain in a tangential direction and exhibit pressing‐enhanced electrical conductivity and polarization loss. The piezoresistive gauge factor (GF) and linearity of the PW aerogels can be adjusted by varying the PPy deposition time, leading to varying GF values in the range of 1.87–4.62. During mechanosensing based on EMI shielding effectiveness (SE), rapid off/on switching between the EM wave transmission and shielding is achieved when the SE varies above and below the effective EMI shielding area (&gt;20 dB) through continuous compression. Such dual‐action electrical/EM off/on wood aerogel switches provide opportunities for the development of advanced smart devices from biomass resources.

Transmission of electromagnetic waves from a plasma globe to a light emitting diode

When introducing students to the topic of energy transported by the electromagnetic field, it is sometimes helpful if both the transmission and reception of signals can be visualized. Here the use of a plasma globe as transmitter and light emitting diode as receiver is described, and how this setup may be used to initiate discussions on central topics of electromagnetic wave propagation.

A compact frequency reconfigurable beam switching antenna based on a single‐layer FSS

AbstractA compact frequency reconfigurable beam switching antenna based on a single‐layer frequency selective face (FSS) is proposed in this paper. The proposed antenna consists of a dual‐band dipole antenna and a single‐layer FSS with hexagonally arrangement. The omnidirectional radiation pattern of the dipole antenna designed as a radiation source and surrounded by the FSS can be converted into directional radiation pattern sweeping along the entire azimuthal plane at two single frequency of 2.4 or 5 GHz. The frequency selection is achieved by controlling the diode state of the FSS unit, and the beam switching is realised by a specific combination of electromagnetic wave reflection or transmission from the hexagonal FSS. The novelty lies in applying the hexagonal arrangement to a dual single‐frequency single‐layer FSS unit. This will not destroy the reflection or transmission characteristics of the FSS unit, but also contribute to reduce the antenna size and achieve a low cost. To validate the design, a prototype is fabricated and measured. The single‐layer FSS antenna with a volume of 57 mm × 57 mm × 58.5 mm can be scanned in 12 steps along the azimuth plane at 2.4 and 5 GHz, respectively.

Programming nonreciprocity and harmonic beam steering via a digitally space-time-coded metamaterial antenna

Recent advancement in digital coding metasurfaces incorporating spatial and temporal modulation has enabled simultaneous control of electromagnetic (EM) waves in both space and frequency domains by manipulating incident EM waves in a transmissive or reflective fashion, resulting in time-reversal asymmetry. Here we show in theory and experiment that a digitally space-time-coded metamaterial (MTM) antenna with spatiotemporal modulation at its unit cell level can be regarded as a radiating counterpart of such digital metasurface, which will enable nonreciprocal EM wave transmission and reception via surface-to-leaky-wave transformation and harmonic frequency generation. Operating in the fast wave (radiation) region, the space-time-coded MTM antenna is tailored in a way such that the propagation constant of each programmable unit cell embedded with varactor diodes can toggle between positive and negative phases, which is done through providing digital sequences by using a field-programmable gate array (FPGA). Owing to the time-varying coding sequence, harmonic frequencies are generated with different main beam directions. Furthermore, the space time modulation of the digitally coded MTM antenna allows for nonreciprocal transmission and reception of EM waves by breaking the time-reversal symmetry, which may enable many applications, such as simultaneous transmitting and receiving, unidirectional transmission, radar sensing, and multiple-input and multiple-output (MIMO) beamformer.

Highly anisotropic MXene@Wood composites for tunable electromagnetic interference shielding

Smart electromagnetic interference (EMI) shielding material with a dynamically adjustable electromagnetic response based on real-time requirements is attractive for future electromagnetic devices. Herein, a highly anisotropic [email protected] composite ([email protected]) with convenient shielding effectiveness (SE) regulation is fabricated by coating MXene on the natural wood surface. Benefiting from the anisotropic pore structure and abundant free radicals, the [email protected] displays a better impedance match in the tangential-section than in the cross-section. In the tangential-section, [email protected] can respond to changes in the dihedral angle between the wood grain and the electromagnetic wave electric field, and achieve the off/on switch between electromagnetic wave transmission and shielding. The SE ranges from 27.4 to 57.6 dB as the dihedral angle alters from 90° (perpendicular) to 0° (parallel). The finite element analysis simulation further reveals the tunable electromagnetic response. This sustainable EMI shielding material based on natural wood offers a novel platform for exploiting intelligent electromagnetic devices.

Ku/Ka Dual-Band Shared-Aperture Leaky-Wave Antenna With Fixed-Frequency and Wide-Angle Beam Scanning Based on Ridged SIW

In this communication, a novel ridged substrate integrated waveguide (RSIW) structure is reported, to realize the transmission of electromagnetic waves in dual bands in a shared aperture. The structure is consisting of two substrate integrated waveguides (SIW) operating in Ka and Ku bands, respectively, by integrating the Ka-SIW into the Ku-SIW like an embedded ridge. Therefore, the Ku-SIW operates like a ridge waveguide with single-mode transmission. Based on the RSIW structure, a leaky-wave antenna (LWA) is developed with fixed-frequency and wide-angle beam scanning in dual bands (Ka and Ku). Two types of slot arrays are arranged on the RSIW, and PIN diodes are adopted to control the states of slots. Two transitions from waveguide to SIW have been designed in Ka and Ku bands, respectively, to excite the RSIW. A binary holographic method based on isotropic-point-source array is developed to quickly obtain the excitation schemes of the slot array for desired beam angles. The measured results verify that the LWA can achieve beam scanning ranges of -72°~39° and -48°~42° at 31.5 GHz and 12.1 GHz, respectively. The proposed RSIW LWA has the feature of dual-band compact shared aperture, and may have a potential application in the dual-band communication systems.

Characteristic Analysis of Cascading-Combination DC/DC Controlled-Source Circuit for Marine Electromagnetic Transmitter

Nowadays marine electromagnetic method is a geophysical method which can effectively explore natural gas hydrate (NGH) resources. This method acquires seafloor structure and distribution laws of mineral resources by transmitting high-power electromagnetic waves to the seafloor, and its detection depth relies on intensity of transmitted electromagnetic waves. At present, marine electromagnetic transmitter is inappropriate for transmission of high-power electromagnetic waves, and therefore, a novel DC/DC controlled-source circuit formed by input-series and output-parallel ZVZCS DC/DC controlled-source circuit units was proposed in this paper, and thus transformation of high-voltage and high-power electric energy was realized by using switching devices with low rated voltage and rated current. Common duty ratio control is adopted to construct small-signal mathematical model of cascading-combination ZVZCS DC/DC controlled-source circuit, influences of parameters on voltage balance at input side and current balance at output side are analyzed. Simulation and experimental results verify that the proposed circuit has favorable voltage and current sharing effect and could satisfy deep exploration requirements of marine electromagnetic transmitter with high transmission voltage.

RIS-Assisted Hybrid Beamforming and Connected User Vehicle Localization for Millimeter Wave MIMO Systems

A reconfigurable intelligent surface (RIS) is a type of metasurface that can dynamically control the reflection and transmission of electromagnetic waves, such as radio waves, by changing its physical properties. Recently, RISs have played an important role in intelligently reshaping wireless propagation environments to improve the received signal gain as well as spectral efficiency performance. In this paper, we consider a millimeter wave (mmWave) vehicle-to-vehicle (V2V) multiple-input multiple-output (MIMO) system in which, an RIS is deployed to aid downlink V2V data transmission. In particular, the line-of-sight path of the mmWave system is affected by blockages, resulting in higher signaling overhead. Thus, the system performance may suffer due to interruptions caused by static or mobile blockers, such as buildings, trees, vehicles, and pedestrians. In this paper, we propose an RIS-assisted hybrid beamforming scheme for blockage-aware mmWave V2V MIMO systems to increase communication service coverage. First, we propose a conjugate gradient and location-based hybrid beamforming (CG-LHB) algorithm to solve the user sub-rate maximization problem. We then propose a double-step iterative algorithm that utilizes an error covariance matrix splitting method to minimize the effect of location error on the passive beamforming. The proposed algorithms perform quite well when the channel uncertainty is smaller than 10%. Finally, the simulation results validate the proposed CG-LHB algorithm in terms of the RIS-assisted equivalent channel for mmWave V2V MIMO communications.

Dielectric Spectroscopy: Revealing the True Colors of Biological Matter

Accurate characterization of biological matter, for example, in tissue, cells, and biological fluids, is of high importance. For example, early and correct detection of abnormalities, such as cancer, is essential as it enables early and effective type-specific treatment, which is crucial for mortality reduction <xref ref-type="bibr" rid="ref1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[1]</xref> . Moreover, it is imperative to investigate the effectiveness and toxicity of pharmaceutical treatments before administration in clinical practice <xref ref-type="bibr" rid="ref2" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[2]</xref> . However, biological matter characterization still faces many challenges. State-of-the-art imaging and characterization methods have drawbacks, such as the requirement to attach difficult-to-find and costly labels to the biological target (e.g., COVID-19 rapid tests), expensive equipment (e.g., magnetic resonance imaging), low accuracy (e.g., ultrasound), use of ionizing radiation (e.g., X-rays), and invasiveness <xref ref-type="bibr" rid="ref3" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[3]</xref> . The characterization of biological matter using microwave ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">µ</i> W), millimeter-wave (mmW), and terahertz (THz) spectroscopy is a promising alternative: it is label-free, does not require ionizing radiation, and can be noninvasive. Moreover, there is a significant difference in how different biological materials absorb, reflect, and transmit electromagnetic (EM) waves <xref ref-type="bibr" rid="ref4" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[4]</xref> that is due to the difference in their dielectric properties. The dielectric properties are described by the frequency-dependent material parameter called the complex permittivity <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathbf{\varepsilon}\left({\mathbf{f}}\right){,}$</tex-math></inline-formula> which expresses how the material responds to an external oscillating electric field. The complex permittivity of a material determines how the material absorbs, reflects, and transmits EM waves at different frequencies ( <xref ref-type="fig" rid="fig1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Figure 1</xref> ). Since each biological material’s permittivity spectrum is different, it acts as an EM fingerprint. A material’s complex permittivity can be calculated from the reflection and transmission of EM waves through the material, described by the S-parameters, which can be measured using a vector network analyzer (VNA) transmitting and receiving EM waves over a range of frequencies. The amplitude and phase of the transmitted and reflected EM waves at different frequencies are influenced by different underlying biological effects at different scales. That causes the entire spectrum to provide information from the supracellular to the molecular and even atomic scale.

Experimental Research and Application of Lightning Protection for Radome

In order to solve the problem of poor compatibility between lightning protection and electromagnetic wave transmittance, a new metal oxide diverter strip was selected in this paper. The breakdown characteristics of the diverter strip were studied by high voltage test, and the layout of the metal oxide diverter strip was designed and optimized by empirical formula. The lightning protection design test was carried out for a type of radome, and the feasibility of the method was verified. This method solves the problem of the radome perforation caused by the large inductive electric field of the antenna and is of great significance for the lightning protection design of the radome and its internal antenna equipment.

Analysis of Information Transmission Characteristics Based on Adaptive Ground Electrode Current Field

The information transmission mechanism of the ground electrode current field uses a very low-frequency electrical signal, which is applied to the two electrodes driven into the soil layer or the collapsed body of the tunnel to form a current field in the rock layer or soil layer. Signal detection is created via the strong penetration of wireless information transmission. This research focuses on various electromagnetic effects, such as polarization, magnetization, and the transmission of electromagnetic waves under the influence of different media, such as rock, sand, reinforced concrete, and air voids. The influence of these adaptive electromagnetic effects on the transmission of electromagnetic waves is mainly reflected in the reflection, refraction, and attenuation of electromagnetic wave signals. The inhomogeneity of the earth medium, the influence of topographic features, and multi-path transmission all cause signal distortion, fading, or changes in the direction of electromagnetic wave propagation. By studying the three physical quantities of magnetic permeability, permittivity, and conductivity, the electromagnetic characteristics of the earth medium are described to research the information transmission characteristics of the earth electrode current field.

Influence of a thin dielectric layer on resonance frequencies of square SRR metasurface operating in THz band

Abstract This article investigates the effect of an additional thin dielectric layer on the top of the metasurface (MS), on the transmission of electromagnetic waves in the terahertz band. For this purpose, the split ring resonator-based MS was designed and analyzed in the terahertz band. The influence of permittivity, film thickness, and suspension height on S 21 transmission coefficient characteristics was studied. For this purpose, a numerical model was created and solved using the finite element method. The conducted study can be helpful in three cases. First, changing the suspension height of the dielectric layer may allow tunable MSs using MEMS structures. Also, this research can be used to determine the effect of applying an additional layer of protection when using the MS as a sensor to test substances that can damage it. In addition, there is an opportunity to study the dielectric properties of thin films using the proposed MS.

Transmission and Scattering Characteristics in Plasma Sheaths of Re-Entry Vehicles Due to Multieffect Synergy

The interaction between electromagnetic (EM) waves and plasma sheaths of reentry vehicles has attracted widespread attention for solving the blackout problem in reentry control and communication. In this article, an integrated model is proposed to study EM wave transmission and scattering characteristics in plasma sheaths for typical altitude and velocity regimes. The key plasma parameters and their distributions of the plasma sheath are investigated based on the previously reported flying data. Reflection, transmission, and absorption coefficients as well as radar cross sections (RCSs) in studied cases are calculated by the integrated model. The results show that multieffects of the plasma sheath, including the high-density, strong-collision, wide-dispersion, subwavelength thickness, etc., can synergistically affect the transmission and scattering characteristics. EM signals of control and communication are then reflected, transmitted, or absorbed differently in various parameter regimes of the plasma sheath. The backward RCS of reentry vehicles may decrease or increase due to variations of feature EM shapes of the plasma sheath. Communication and control properties of the reentry vehicles are also revealed by synergy of multieffects of the sheath on EM waves in various regimes.