Excitation Of Electromagnetic Waves Research Articles

Solution of electromagnetic scattering field of adjacent transmission towers based on reciprocity theorem

Due to the large number of transmission towers being built, the dense distribution of transmission towers is inevitable in some areas. Densely distributed transmission towers will generate severe electromagnetic coupling, which will affect the setting of the passive interference protection distance between transmission towers and adjacent radio stations. Therefore, based on the traditional algorithm for solving the electromagnetic scattering field of a single electrically large target in wide area space, the electromagnetic coupling effect between multiple adjacent transmission towers within a range of 10 times the signal wavelength was considered. Based on the reciprocity relationship between the scattering electric field and the source and the introduced auxiliary field source as the intermediate variable, the electric field integral equation of the secondary scattering field generated by the electromagnetic coupling effect of adjacent transmission towers was derived, and the secondary scattering field is superimposed with the primary scattering field of the transmission generated by the electromagnetic wave excitation of the radio station, obtaining the electromagnetic scattering field at any point. In order to verify the accuracy of the algorithm proposed in this article, the scaled model experiments for the electromagnetic coupling effect between two transmission towers in an anechoic chamber were conducted. The average error of the algorithm proposed in this article is 6.73%, while the error of traditional algorithms is 20.18%. Compared with the traditional algorithm, the accuracy of the proposed algorithm is improved by 13.45%.

Composite metamaterial antenna with super mechanical and electromagnetic performances integrated by three-dimensional weaving technique

The integration of structure and function was crucial for the application of microstrip antennas. Layered microstrip antennas were prone to delamination, which severely limits their performance stability. The textile conformal microstrip antenna with integrated structure design prevented the layered failure and greatly improved the damage resistance of the antenna. However, textiles had an inherent deficiency in suppressing surface waves due to their discontinuous mesh structure, critically deteriorating the radiation performance of microstrip antennas. Electromagnetic metamaterial with a specific pattern resonated in the excitation of electromagnetic waves to form a forbidden bandgap, which was expected to suppress surface wave radiation of microstrip antennas. In this study, a textile-based microstrip antenna integrated with electromagnetic metamaterials (MA-EBG) was proposed by embedding conductive copper wires in three-dimensional (3D) spacer fabric to form an integrated structure. Due to the function of the forbidden bandgap in metamaterial structure, the surface wave radiation was suppressed and the gain of antenna was increased from 5.1 dB to 9.6 dB. Owing to the tight physical binding, MA-EBG retained its structural integrity with proper electromagnetic performance under the impact of 24 J. The application of electromagnetic metamaterials elevated the gain of textile-based microstrip antennas, which provided a new method for the design of high-gain textile-based microstrip antennas with excellent mechanical properties.

Experimental detection of topological surface waves at a magnetized plasma interface in the Voigt configuration

This Letter reports on the experimental observation of a topologically non-trivial electromagnetic wave propagating perpendicular to an applied magnetic field at the interface between a gaseous plasma and metal. The resulting one-way wave-guiding is a demonstration of topological non-reciprocity associated with the edge state within the gap between the lower and upper X-modes of the bulk plasma. Electromagnetic wave excitation using simple dipole antennas results in a 20 dB isolation at 10.8 GHz with the plasma biased with a magnetic field of 87 mT. We show that reducing the magnetic field gradually diminishes the strength of the transmitted wave due to the closing of the X-mode gap.

Features of backward waves and negative refraction in absorbing bi-isotropic media and metamaterials

ABSTRACT Conditions of the excitation of backward electromagnetic waves and negative refraction in absorbing bi-isotropic layered media and metamaterials are investigated. Based on the exact analytical model, the features determined by absorption and inhomogeneity of the waves and possible metamaterial properties of the medium are ascertained. It is shown that only simultaneous realization of backward, backward with respect to the boundary between two media, and negative refraction is possible for each of the proper waves in a bi-isotropic layer. The conditions are obtained when two (one transmitted and one reflected waves) or all the four proper waves in the layer are backward and characterized by negative refraction on boundaries. Taking into account the calculation of Pointing’s vector and energy dissipation of the waves, it is shown that the well-known limitations on the chirality and nonreciprocity parameters require a clarification for the considered media.

Propagation of visible light in nanostructured niobium stripes embedded in a dielectric polymer

Abstract Nanometric metallic stripes allow the transmission of optical signals via the excitation and propagation of surface-localized evanescent electromagnetic waves, with important applications in the field of nano-photonics. Whereas this kind of plasmonic phenomena typically exploits noble metals, like Ag or Au, other materials can exhibit viable light-transport efficiency. In this work, we demonstrate the transport of visible light in nanometric niobium stripes coupled with a dielectric polymeric layer, exploiting the remotely-excited/detected Raman signal of black phosphorus (bP) as the probe. The light-transport mechanism is ascribed to the generation of surface plasmon polaritons at the Nb/polymer interface. The propagation length is limited due to the lossy nature of niobium in the optical range, but this material may allow the exploitation of specific functionalities that are absent in noble-metal counterparts.

Localized Excitation of Electromagnetic Ion Cyclotron Waves From Anisotropic Protons Filtered by Magnetic Dips

AbstractThe excitation of electrostatic and/or electromagnetic waves in the plasma universe is often associated with anisotropic velocity distributions of charged particles. In Earth's inner magnetosphere, this anisotropy can gradually develop as particles injected from the magnetotail drift around the Earth at different speeds depending on their energy and pitch angle. Here, we show that the perpendicular‐moving and bouncing ions can be separated more abruptly near the injection front. These pitch‐angle filters are localized magnetic dip structures formed by the diamagnetic behavior of the injected particles, which can trap perpendicular‐moving ions and allow bouncing ions to overtake. The resulting ion anisotropy facilitates the rapid generation of electromagnetic ion cyclotron (EMIC) waves, which in turn can largely reshape the Van Allen radiation belts. This scenario is examined by case and statistical observations, together with numerical simulations that reproduce most of the observational signatures, to support the causal relationship between magnetic dips, anisotropic ion distributions, and localized excitation of EMIC waves. Our study highlights the important roles of magnetic dips in the inner magnetospheric dynamics, as pitch‐angle filters of the injected ions and traveling hotspots of EMIC wave activities.

The Use of Plasmonic Spectroscopy for Detecting Ultra-Low Concentrations of Substances

This paper presents the results of research into the excitation of a surface electromagnetic wave (SEW) in Au/AgI and Au/Ag films contacting aqueous solutions of hydrogen peroxide (H2O2) and sodium chloride (NaCl). The dependences of the SEW excitation angle in the Kretschmann configuration on the interaction time of the solution with the metal film have been obtained. The effect of an aqueous H2O2 solution on the AgI and Ag film under prolonged exposure has been demonstrated. It has been shown that the dynamics of the excitation angle can be used to estimate the concentration of solutions with low and ultra-low concentrations. As an example, the results of using the technique for the analysis of aqueous solutions of NaCl are presented.

On Cherenkov excitation of electromagnetic waves by vortex travelling in Josephson sandwich

The intensities of two types of Cherenkov waves arising at the motion of a solitary vortex along a Josephson sandwich are compared. These waves arise in the tail part of the vortex or are emitted deep into the medium surrounding the sandwich. The vortex velocities at which one of these two types of waves excited by the Cherenkov mechanism dominates are determined.

Ponderomotive force driven mechanism for electrostatic wave excitation and energy absorption of electromagnetic waves in overdense magnetized plasma

The excitation of electrostatic waves in plasma by laser electromagnetic (EM) pulse is important as it provides a scheme by which the power from the laser EM field can be transferred into the plasma medium. The paper presents a fundamentally new ponderomotive pressure-driven mechanism of excitation of electrostatic waves in an overdense magnetized plasma by a finite laser pulse. Particle-in-cell simulations using the EPOCH-4.17.10 framework have been utilized for the study of a finite laser pulse interacting with a magnetized overdense plasma medium. The external magnetic field is chosen to be aligned parallel to the laser propagation direction. In this geometry, the EM wave propagation inside the plasma is identified as whistler or R and L waves. The group velocity of these waves being different, a clear spatial separation of the R and L pulses are visible. In addition, excitation of electrostatic perturbation associated with the EM pulses propagating inside the plasma is also observed. These electrostatic perturbations are important as they couple laser energy to the plasma medium. The excitation of electrostatic oscillations are understood here by a fundamentally new mechanism of charge separation created by the difference between the ponderomotive force (of the EM pulse) felt by the two plasma species, viz., the electrons and the ions in a magnetized plasma.

Research on Permanent Magnet-Type Super-Low-Frequency Mechanical Antenna Communication

In the super-low-frequency ( 30 ∼ 300 Hz ) band communication, the traditional antenna covers a large area and has low radiation efficiency. The excitation of electromagnetic waves by the mechanical motion of permanent magnets enables miniaturized technology for super-low-frequency communication. For this miniaturization technique, this paper proposes a super-low-frequency communication architecture framework. Theoretical analysis and experimental verification of each unit module in the structural framework are carried out to achieve high-quality communication. For the radiation unit, permanent magnet parameters and communication distances are introduced to establish a rotating permanent magnet radiation power analysis model and to study the radiation characteristics of rotating permanent magnets. For the receiver unit, a sensitivity normalization characterization method based on the ratio of the coil thermal noise voltage to the induced voltage is proposed. Based on the sensitivity analysis model, a square coil was developed that meets the communication requirements of a mechanical antenna and an experimental platform was built. Experiments are conducted on the factors affecting radiated power and coil sensitivity, and 2FSK signal modulation communication experiments are conducted to verify the feasibility of the communication structure framework. The volume of the mechanical antenna permanent magnets in the experiment is all below 10 cm3, and the operating frequency is continuously adjustable from 0 to 250 Hz. The experimental results show that the near-field radiated power of a rotating permanent magnet is proportional to square of the volume of the rotating permanent magnet; the sensitivity of the coil is proportional to the number of turns and the area of the coil. By controlling the speed in real time, you can control the frequency of the signal and modulate it.

Multilayer graphene frequency doubler using direct-current bias and reflector networks

A multilayer graphene frequency doubler (GFD) with inductance–capacitor resonators (LCRs) and microstrip reflective stubs (MRS) is proposed in this paper. Graphene has strong nonlinear characteristics. Under the excitation of electromagnetic waves, the output power of odd harmonic of graphene is greater than that of even harmonic. Under the joint excitation of electromagnetic wave and bias voltage, the even harmonic output power of graphene is enhanced and the odd harmonic is suppressed, which is very suitable for making GFD. On the basis of analyzing the conductivity of graphene, the symbolically defined device model of multilayer graphene is established, and the model is applied to GFD circuit, the simulation results are basically consistent with the experimental data. The multiplier efficiency of graphene can be effectively improved by the bias voltage and LCR and the MRS. At an operating frequency of 0.65–1.15 GHz, the minimum conversion loss (CL) of the GFD is 20.57 dB when the input power is 16 dBm.

The Effect of Ion-to-Electron Mass Ratio on the Electron Beam-Plasma Interaction

Two-dimensional electromagnetic particle-in-cell simulations are carried out to investigate the effect of ion-to-electron mass ratio on the evolution of warm electron beam-plasma instability. Four cases are considered: A: mi/me = 0 (two-electron stream instability); B: mi/me = 1 (pair plasma); C: mi/me = 100; and D: mi/me = 1000. It is shown that the generation of Langmuir waves in the fundamental mode of electron plasma frequency and the subsequent dynamics of large-amplitude solitons are not affected by the ion species. However, it determines the decay process of solitons and the excitation of electromagnetic waves in the second harmonic. In the first two cases, mi/me = 0 and 1, there is no sign of emission in the second harmonic, while the strongest emission in the second harmonic is found for the case of largest mass ratio, mi/me = 1000. This confirms the two-step wave-wave coupling mechanism for the generation of second harmonic electromagnetic waves, which requires the excitation of ion-acoustic waves in the first step. Moreover, the dispersion diagrams of all excited waves are presented.

Взаємодія хвиль і частинок при інжекції модульованого електронного пучка в іоносферну плазму. Теорія та експеримент

We present the results of the active space experiment with charged particle beam's injection (electrons and xenon ions) carried out onboard Intercosmos-25 station and daughter Magion-3 subsatellite. The ones are obtained under conditions when the particle beams were injected in opposite directions relative to the magnetic field B0 in such a way that the electron injection was directed towards the Earth. Mechanisms of beam-plasma instabilities relative to the excitation of electrostatic and electromagnetic waves are considered during the electron beam injection (~10 keV, 0.1 A) from the Intercosmos-25 station. Development of transverse instability on the first cyclotron resonance leads to the excitation of whistler mode waves backward-propagating relative to the injected electrons (from the Earth). The investigation object was the beam-excited differential fluxes of ionospheric electrons in a wide energetic range of 27 eV — 412 keV registered by the charged particle spectrometers onboard the Magion-3 subsatellite. Thereby, the interaction of whistler waves with ionospheric electron fluxes is stimulated by the energy transfer mechanisms such as 'particle-wave-particle'. Numerical results of beam-plasma instabilities are compared also with thermal plasma parameters registered at different space points on the station and subsatellite. Excitation of longitudinal and transverse beam-plasma instabilities will inevitably lead to their competition, which will affect the results of the experiment. The data of stimulated fluxes of ionospheric electrons allow us to investigate the various effects of the wave-particle interaction, taking into account the influence of the growth rate of longitudinal instability on the excitation angle of whistlers and their structure. This approach is based on the results of laboratory experiments to determine the pattern of excited whistlers for an electric dipole antenna and the analogy of the beam-plasma channel with the radiating system. The results of the active space experiment confirm the dependence of the growth rate of whistler mode waves on the development of longitudinal beam instability.

Report on VERSIM 2020

The 9th VLF/ELF Remote Sensing of Ionospheres and Magnetospheres Workshop (VERSIM 2020) was successfully held as a virtual meeting during the week of 16–20 November 2020. The meeting had been rescheduled from the original meeting (23–27 March 2020 at the Uji Campus, Kyoto University, Japan), cancelled due to the COVID-19 pandemic. The VERSIM workshop aims to bring together scientists from all across the globe to present and discuss topics related to the excitation, propagation, and effects of electromagnetic waves in the ELF/VLF (300 Hz – 30 kHz) range. The VERSIM group was established as a joint URSI/IAGA work group in 1975. It has been the main scientific body to specifically focus on whistlers in the Earth's ionosphere and magnetosphere (whistler waves were one of the first electromagnetic signals detected by ground instruments, and gave important clues about the Earth's active space environment). The scope of this group has grown substantially over the years. It has grown particularly in recent years with the recognition that whistler-mode chorus and hiss waves play a particularly important role in shaping the dynamics of the Earth's high-energy radiation belts (particularly topical in light of the continuing successful operation of the Van Allen Probes and the Arase (ERG) spacecraft). Whistler waves are also known to be intimately involved in the magnetic reconnection process (which is currently very topical due to the launch of the MMS satellite) and solar flaring. In addition to the traditional VERSIM topics, results of recent space missions, such as Arase, MMS, and the Van Allen Probes, were presented.

Semianalytical Solution for Determination of Wave Amplification Characteristics in a Complex Elliptical Dielectric Waveguide Including Strongly Magnetized Plasma Circular Column

In this research, the excitation of hybrid electromagnetic waves in a complex dielectric-plasma waveguide is investigated semianalytically using the perturbation method and applying the suitable boundary conditions. Under this study waveguide combines circular and elliptical geometries, eccentrically. This elliptical waveguide has been filled with a dielectric material, whereas two axial hollows with circular section have been created in its focuses. In one of the hollows, there is an axial strongly magnetized plasma and a relativistic solid circular electron beam (RSCEB) is injected inside the other hollow. In addition, the growth rate of slow waves amplified by the electron beam is numerically calculated. The effects of accelerating voltage, current density of RSCEB, and geometrical parameters, such as radii of plasma column and electron beam, on the growth rate, electric field profile, and the frequency spectra are studied. Finally with considering the results, we will propose the optimum configuration to obtain maximum amplification of slow waves.

Dual-band microwave resonators based on cross hollow structures for refractive index sensing

We numerically and experimentally studied the electromagnetic characteristics of a suitably designed planar metamaterial which composed of cross hollow structures. The results show that two sharp transmission dips with quality factors of 7.93 and 19.3 can be generated in the microwave region under the excitation of normal incident electromagnetic wave. And if its surface is covered by 2 mm thick analyte, both of the two transmission dips show linearly spectral shift with the change of the analytes’ refractive index. Using the two resonances as the identifiers, the calculated average refractive index sensitivities are 1.116 GHz/refractive index unit (RIU) and 2.357 GHz/RIU, with corresponding figure of merits (FOM) of 1.87 and 4.9. It offers a potential for sensing detection and provides a reliable reference for the design of excellent plasmonic sensors.

ON GENERATION OF A WAVE PACKAGE IN A WAVEGUIDE, FILLED ACTIVE MEDIUM

Excitation of electromagnetic waves in a waveguide with a medium, which is a two-level system, is considered. To describe the processes, both classical electrodynamics methods and quantum mechanics methods are used. The nature of the processes under study turns out to depend on the relationship between the Rabi frequency and the line width of the excited wave packet. It is shown that if the field energy density is high, then spatially inhomogeneous Rabi frequencies arise, which leads to oscillatory behavior of the wave field amplitudes. If the levels of the excited field are small, then the dynamics of the two-level quantum system becomes monotonic and the population inversion tends to zero.

Carbon-Based Composite Microwave Antennas

Applications of metamaterials to microwave antennas are reviewed over the past decade. The manufacturing of microwave antennas using graphene-containing carbon composite materials was developed and prototypes of dipole and horn antennas made from such materials were created. The radiation properties of the designed antennas and their metal analogs were measured and compared. The standing wave ratios, the radiation patterns and the amplitude-frequency characteristics were analyzed for horn antennas at frequencies 1.6 GHz and 5 GHz and for dipole antennas in the frequency range 0.2–0.6 GHz. The polarization characteristics of the horn antennas were studied. The effects of different carbon composite materials’ structures (fiber or fabric) on the antennas’ parameters were estimated. It is shown that antennas made from graphene-containing composite materials are able to operate efficiently and exhibit almost the same radiation properties as conventional metal antennas of the same geometry and size. However, the carbon-based antennas have much smaller weights and enhanced stability in a wide range of temperatures. In the future, such antennas should replace the conventional ones for many applications, especially for the excitation and reception of electromagnetic waves in space plasmas.

Антенная система диапазонов сверхвысоких и крайне высоких частот с широкоугольным сканированием

Two variants of dual-band antenna systems with a common aperture are considered and compared. The common is that in the both variants there are used: two-reflector system with rotation of polarization plane for exсitation of extremely high frequency band electromagnetic waves and slotted-waveguide array for excitation of microwave frequency band electromagnetic waves. Twist-reflector of extremely high frequency band is combined with aperture of slot-waveguide array. The difference of the proposed variant of antenna system is use of a flat transreflector and a twistreflector, which is a multi-element polarization array and has little effect on the characteristics in the microwave range. The structure of flat transreflector is based on multi-layer zoned Frenel antenna. The both variants of antenna system allow to realize a wide-angle space scanning. Manufacturing of antenna system with flat multi-layer transreflector is greatly simplified with the help of well-developed technology for the production of printed circuit boards. There are presented the results of computer simulation that show the possibility of practical realization of the proposed antenna systems.

Resonant absorption of terahertz waves in layered superconductors: Wood's anomalies and anomalous dispersion

We study theoretically the resonant absorption of terahertz electromagnetic waves of TM polarization in a slab of layered superconductor enclosed within twofold dielectric layers. Using the transfer-matrix method and assuming weak dissipation of waves in the sample, we analyze the absorption for both symmetric and antisymmetric bilateral incident radiation. The excitation of electromagnetic waves localized on layered superconductors gives rise to resonant absorption, a phenomenon known as Wood's anomaly, providing for suppression of the specular wave reflection. This phenomenon is essentially modified in the layered superconductors as compared with usual conductors. The dispersion curves of localized modes are nonmonotonic, thus resulting in the specific dependence of the absorptance $A$ on the incidence angle $\ensuremath{\theta}$. We reveal the conditions for emergence of the resonant absorption and derive the asymptotic expressions for the resonant absorptance. A specific non-Lorentzian line shape of $A(\ensuremath{\theta})$ dependence, like twin resonant peaks or a merged single broad peak, appears when the wave frequency $\ensuremath{\omega}$ is tuned close to the top point on the dispersion curve $\ensuremath{\omega}(\ensuremath{\theta})$. Experimental observation of such resonant line shapes can serve as a verification of the existence of localized waves with nonmonotonic dispersion in the layered superconductors.