EM Wave Propagation Research Articles

Ground experimental study of the electron density of plasma sheath reduced by pulsed discharge

Abstract A plasma sheath will be generated around the hypersonic vehicle during reentry, where a large number of electrons will significantly affect the propagation of EM waves, resulting in the phenomenon of communication blackout. This paper proposes a method of reducing the electron density of reentry vehicle plasma sheath by pulsed discharge. Experiments were conducted in a high-speed plasma wind tunnel to study the effects and scope of pulsed discharge on the plasma sheath electron density using an ultrahigh-speed camera and microwave diagnostic system. The experimental results show that the application of pulsed discharge resulted in the formation of a light intensity attenuation region measuring 14 × 19 × 4 cm around the discharge area, with an attenuation degree ranging from 30% to 58%. The microwave diagnostic results indicate that after the actuator discharge, the electron density of the plasma sheath within a 4 cm height above the vehicle wall is significantly reduced compared to before the actuator discharge, with a maximum reduction of approximately 86%. These results demonstrate that this method has significant effects on reducing plasma sheath electron density. Furthermore, the low power consumption, load, and space requirements suggest that it has potential for practical applications.

The Impact of an Electric Machine Body on EM Wave Propagation in RTMS

The metallic components of an electric machine exert a notable impact on the electromagnetic transmission between an external recipient and an internal shaft sensor. The RTMS (rotor temperature monitoring system) is aimed at boosting power transfer in the machine, regardless of the considerable impact of its components. This research assesses the influence of the components of an electric machine on shaft sensor transmission and specifically addresses the packaging needs of the receiver antenna. The study includes a comparative analysis of two antennas. HFSS (high frequency structure simulator) simulation was utilized to identify the antenna with a superior propagation factor. The principal contribution of this paper is the assessment of how the electrical machine body affects the transmission and propagation of rotor sensor signals, establishing a connection between these effects and the packaging criteria for the receiver antenna. Moreover, the paper presents an antenna design that capitalizes on the electrical machine body to enhance the power transmission effectiveness. The final section of this paper encompasses the experimental results obtained from the implementation of the RN171 antenna on the electrical machine, provides valuable insights into the propagation characteristics, and contributes to a comprehensive understanding of the electromagnetic dynamics within the system.

Galerkin Method and Parallel Algorithm for Solving the Problem of EM-Wave Propagation in a Locally Inhomogeneous Medium with a Graphene Layer at the Boundary of the Inhomogeneity Domain

Galerkin Method and Parallel Algorithm for Solving the Problem of EM-Wave Propagation in a Locally Inhomogeneous Medium with a Graphene Layer at the Boundary of the Inhomogeneity Domain

Reciprocal and non-reciprocal electromagnetic wave propagation in sub-100 nm epitaxial YIG thin films deposited under different oxygen growth pressure

Directional dependent transport of information in magnetic thin films offers a great opportunity to realize reciprocal and nonreciprocal microwave devices, such as filters, phase shifter, isolators and circulators. Electromagnetic wave (EM) propagation in sub-100 nm thin magnetic film is critical, yet reciprocal and non-reciprocal wave propagation and its accurate measurements remain a challenge. We investigated reciprocal and non-reciprocal wave propagation in 90 nm thick epitaxial thin films of yttrium iron garnet (Y3Fe5O12:YIG) grown by pulse laser deposition (PLD) technique on gadolinium gallium garnet [GGG(100)] substrates. The effect of oxygen growth pressure during deposition of YIG films exhibit directional dependence properties of electromagnetic wave propagation. The reciprocal EM wave propagation was generated by a S-type transmission line to achieve microwave (RF) magnetic fields (hRF) perpendicular to applied dc magnetic fields (HDC), to ensure the ferromagnetic resonance (FMR) condition. The center frequency is tuned up to 20 GHz with an applied magnetic field of 6 kOe. The tuning of the center frequency was achieved as of 85.3 % with HDC of 6 kOe. To achieve non-reciprocal EM-wave propagation one straight microstrip line was used to ensures a parallel configuration (parallel pumping FMR condition) of hRF to HDC. The nonreciprocity observed is due to the presence of gyrotropic properties in the YIG thin films and it enhances when YIG film was placed in asymmetric geometry. Further, oxygen growth pressure (>0.1 mbar) grown YIG films enhances the nonreciprocity by 21.6 %. The experimental results were successfully validated using high-frequency structure simulator (HFSS). Hence, these results indicate that controlled deposition parameters can be a crucial parameter in the design of reciprocal and nonreciprocal microwave signal processing devices.

Analysis of Radar Target Scattering Echo With Surface Ducting in Large-Scale Environments Based on the PE-MoM Hybrid Method

This letter proposes a three-dimensional (3-D) PE- MoM hybrid method to predict radar target scattering with sur- face ducting in large-scale environments. The method divides the complex multiscale problem into two sub-problems: electromag- netic (EM) wave propagation and scattering. The bidirectional 3-D parabolic equation (PE) method is used to consider the influence of environmental factors such as irregular terrain and atmospheric duct on EM wave propagation, while the method of moments (MoM) is used to calculate the scattering from the key target. By introducing phase compensation and Fourier synthesis techniques, the proposed method can be extended to predict transient scattering echoes from the target. A typical example is given to verify the correctness of the proposed method, and good consistency is also seen from comparison with the MoM. Finally, simulation analysis is carried out for the scattering of a missile target in a sea-land composite environment. The results show that the proposed method can effectively predict the scattering echoes of low-altitude targets in large-scale environments.

Harmonic generation in magnetized plasma for electromagnetic wave propagating parallel to external magnetic field

Harmonic generation has always been of fundamental interest in the study of the nonlinear nature of any physical system. In the present study, particle-in-cell simulations have been carried out to explore the harmonic generation of electromagnetic (EM) waves in a magnetized plasma. EM wave propagation is chosen to be parallel to the applied external magnetic field. The simulations show the excitation of odd higher harmonics of right circularly polarized waves and left circularly polarized waves when the incident wave is linearly polarized. The harmonic generation is maximum when the incident EM wave frequency matches the electron cyclotron frequency. When the incident EM wave has a circular polarization, no harmonics get excited. A theoretical understanding of these observations has also been provided. The studies thus show that by appropriately tailoring plasma parameters, EM waves of higher frequencies and the desired nature of circular polarization can be generated.

Investigation of Creeping Wave Characteristics Using Cross-Slot Antenna on 12-Cylinder Phantom Model

This letter presents the systematic study of the EM wave propagation in on to on-body involving the 12-cylinder phantom model, which aids in static as well as dynamic system modeling using systematic simulation and experimental measurements. The 12-cylinder phantom model is a simplified human body model featuring the critical parts of human body. For the study of on-to on-body transmission characteristics two cross-slot antennas having omnidirectional radiation pattern are used. An in-depth investigation of creeping waves and double arm swing activity using the 12-cylinder model under different configurations and dynamic situations are executed with transmission characteristics.

The Effects of Rainfall on Over-the-Horizon Propagation in the Evaporation Duct over the South China Sea

The evaporation duct (ED) is generated by the evaporation of seawater and can be an influential factor of electromagnetic (EM)-wave propagation. Rainfall also affects atmospheric factors and EM-wave propagation. However, the distribution of the ED and path loss (PL) during rainfall has rarely been reported. This paper analyzes the distribution of the atmospheric factors and ED in the South China Sea (SCS). The results show that the evaporation duct height (EDH) in the area of rainfall is generally lower. The effect of the ED on the over-the-horizon (OTH) propagation reaches 0.69 dB km−1 on average, which is 4.3 times stronger than the maximum rain attenuation (0.16 dB km−1) when the rainfall is less than 5 mm h−1. In the SCS, a 53 km long OTH link was established between Donghai Island and Jizhao Bay to observe the PL. The measurement results show that the nearly saturated relative humidity (RH) leads to a high PL. The results also show that the change in the direction of the sea–land breeze causes a 42.4 dB decrease of PL by transferring the moist patches. Rainfall has an attenuation effect on OTH propagation in ED, mainly owing to the high RH.

A New Lattice Boltzmann Scheme for Photonic Bandgap and Defect Mode Simulation in One-Dimensional Plasma Photonic Crystals

A novel lattice Boltzmann method (LBM) with a pseudo-equilibrium potential is proposed for electromagnetic wave propagation in one-dimensional (1D) plasma photonic crystals. The final form of the LBM incorporates the dispersive effect of plasma media with a pseudo-equilibrium potential in the equilibrium distribution functions. The consistency between the proposed lattice Boltzmann scheme and Maxwell’s equations was rigorously proven based on the Chapman–Enskog expansion technique. Based on the proposed LBM scheme, we investigated the effects of the thickness and relative dielectric constant of a defect layer on the EM wave propagation and defect modes of 1D plasma photonic crystals. We have illustrated that several defect modes can be tuned to appear within the photonic bandgaps. Both the frequency and number of the defect modes could be tuned by changing the relative dielectric constant and thickness of the defect modes. These strategies would assist in the design of narrowband filters.

Hybrid Simulation Method for EM Wave Generation and Propagation of Streamer Discharges

The finite-difference time-domain (FDTD) method has been widely used for analyzing the EM wave propagation property of partial discharge (PD). However, many studies use Gaussian pulse as the excitation source, which shows few theoretical relations with the EM wave generation mechanism of PD. To simulate the EM wave generated by PD, the electric field distortion caused by the streamer discharges is analyzed. The finite element method (FEM) is used to calculate the fluid model to get the electric distribution alongside the charged air gap. This distorted electric field obtained from the fluid model is applicable as an excitation source of EM wave, which also explains its generation mechanism caused by the time-varying electric field. Because of the limitations of FEM, such as one frequency response and the huge computation complexity for large electric size. FDTD method is a useful tool to approximate Maxwell's curl equations and simulate the EM wave generated by the distorted electric field. In contrast to typical FDTD applications with one excitation, several excitation points should be chosen to simulate the distorted electric field, and they are evenly distributed alongside the streamer path since the EM wave is emitted by a charged gap rather than a point. Thus, this paper proposes a hybrid method that combines FEM and FDTD for the whole process simulation of the EM wave caused by PD. A positive streamer under two types of electrodes is simulated and the frequency spectrums of generated EM time-domain waveforms are also obtained. The proposed method simulates the EM radiation of PDs digitally, which provides a reference for PD monitoring.

Far-field characterization of wave oblique incidence on body channel for implant communication by using an analytical model

Characterization of human body channel is a necessity to pave way for the practical implementation of implant communication. Considering there are few investigations on the characterization of incident wave propagating at an arbitrary angle to human tissues, this paper applies an analytical model of wave oblique incidence onto multilayered planar lossy tissues to evaluate the far-field EMFs and PLs of body channel. With this model, EMFs and PLs of both TM and TE wave oblique incidence at different angles and frequencies in out-to-in and in-to-out propagations are calculated. A FEM model and a measurement on porcine tissues are also carried out. Comparing with simulation and experiment, the analytical results of PLs have the maximum differences of 0.03 and 1.0 dB, respectively, in out-to-in propagation and of 0.09 and 1.7 dB, respectively, in in-to-out propagation. Therefore, the analytical model is accurate and indicates the mechanism of EM wave propagation in body channel theoretically.

Accurate and Efficient Finite-Difference Time- Domain Formulation of Dusty Plasma

The finite-difference time-domain (FDTD) method has been widely used for the electromagnetic analysis of complex dispersive media. The shift-operator (SO)-FDTD or auxiliary differential equation (ADE)-FDTD formulation has been mainly employed for dusty plasma. Each FDTD formulation has its pros and cons. SO-FDTD is accurate but not computationally efficient. ADE-FDTD needs fewer computational resources, but its accuracy is poor. Here, we propose an accurate and efficient FDTD formulation for dusty plasma, based on the bilinear transform (BT). We perform a comprehensive study on the numerical permittivity and the computational efficiency for three FDTD formulations. Numerical examples are employed to illustrate that the proposed BT-FDTD outperforms the previously reported FDTD formulations for dusty plasma. In addition, based on the proposed BT-FDTD simulations, the effect of dust particles on EM wave propagation is investigated in the GHz band and the THz band.

Studies on the propagation properties of THz wave in inhomogeneous dusty plasma sheath considering scattering process

The plasma sheath formed during the reentry process is able to block the detection and communication to the hypersonic vehicle. Various of interactions occur during the propagation of EM wave in the plasma sheath. In addition, the dusty particles formed during the ablation of the protective layer make this process more complicated. Dusty plasma sheath is an important factor that affect the detection of hypersonic vehicle. In this work, the propagation properties of THz wave in inhomogeneous dusty plasma sheath are studied. The flow field distribution around the hypersonic vehicle is simulated first. Then the electron density is calculated using equilibrium constant method of the 7-species reacting air model. And the collision frequency is calculated based on the results of the flow field simulation. The absorption and scattering process are studied using scattering matrix method and Mie scatter theory, respectively. The propagation properties are calculated considering the influences of the flight speed, the flight altitude, the radius, the number density and the kind of the ablation particles. The calculation results show that with the increase of THz wave frequency, the transmittance increases firstly and then oscillates. The shape of the transmittance curve is determined by the flight speed, the flight altitude, the radius, the number density and the kind of the ablation particles. The main loss mechanisms in different wave bands has also been discussed and the optimum transition band is given. This work shows that THz wave has good potential applications in hypersonic vehicle detection. It also provides a method to select the optimum detection frequency band.

Study Interprets Electromagnetic-Wave Penetration, Absorption for Bitumen Reservoir

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 199941, “Interpretation of Electromagnetic-Wave Penetration and Absorption for Different Reservoir Mineralogy - Quartz-Rich, Limestone-Rich, and Clay-Rich - and at High- and Low-Water Saturation Values for a Bitumen Reservoir,” by Matthew Morte, SPE, Hasan Alhafidh, SPE, and Berna Hascakir, SPE, Texas A&M University, prepared for the 2020 SPE Canada Heavy Oil Conference, originally scheduled to be held in Calgary, 18–19 March. The paper has not been peer reviewed. Interpretation of logging data generated through electromagnetic (EM) waves or determination of EM-wave propagation in a medium as an enhanced-oil-recovery (EOR) method are not easy tasks. The complete paper aims to identify the role of different geological settings with different types of fluid saturations in the response of EM-wave propagation and absorption. Several correlations were created in this study and can be used to better interpret the reservoir mineralogy and fluid saturation as a response to EM-wave logging. Moreover, these results can be used to estimate the effective area (penetration depth) of EM waves as an EOR method. Experimental Procedure Complex permittivity of synthesized rock samples was recorded by means of a vector network analyzer as the source and a dielectric probe kit as the transmitter. The dielectric probe behaves as both the transmitter and receiver simultaneously by measuring the proportion of the reflected wave. The dielectric probe is capable of measuring both the solid interface, as is the case with the synthesized reservoir rock, and fluids. The output of the vector network analyzer is both the dielectric constant, defined to be the real-portion complex permittivity, and the loss index, defined to be the imaginary portion. The loss tangent is a parameter that describes the overall efficacy of the material as a microwave absorber with higher values corresponding to higher heat generation in the reservoir. Reservoir properties of interest are isolated by taking advantage of experimentally defined synthesized cores. Variable properties are achieved by introducing a known quantity of specified materials to ensure control over the outcome of representative reservoir rock. Samples are an unconsolidated mixture of both the skeletal frame (rock matrix) as well as the pore space. The rock matrix is comprised of a systematic and stepwise variability of quartz sand, limestone sand, and kaolinite clay or bentonite clay. The fraction of each introduced mineral is manipulated to isolate the contribution of the individual components. The weights of the introduced constituents are calculated to result in a synthetic rock matrix with the desired rock mineralogy. The first batch of synthesized cores consisted of 75 mixtures. The remainder of the contrived cores were limestone. A separate 20 experiments were performed to account for the presence of both pore-filling and swelling clays, namely kaolinite and bentonite, respectively. Compaction and blending of the cores were performed by hand; homogenization of the mixture was ensured by thorough mixing.

A fast local embedded boundary method suitable for high power electromagnetic sources

High power sources of electromagnetic energy often require complicated structures to support electromagnetic modes and shape electromagnetic fields to maximize the coupling of the field energy to intense relativistic electron beams. Geometric fidelity is critical to the accurate simulation of these High Power Electromagnetic (HPEM) sources. Here, we present a fast and geometrically flexible approach to calculate the solution to Maxwell’s equations in vector potential form under the Lorenz gauge. The scheme is an implicit, linear-time, high-order, A-stable method that is based on the method of lines transpose (MOLT). As presented, the method is fourth order in time and second order in space, but the A-stable formulation could be extended to both high order in time and space. An O(n) fast convolution is employed for space-integration. The main focus of this work is to develop an approach to impose perfectly electrically conducting (PEC) boundary conditions in MOLT by extending our past work on embedded boundary methods. As the method is A-stable, it does not suffer from small time step limitations that are found in explicit finite difference time domain methods when using either embedded boundary or cut-cell methods to capture geometry. This is a major advance for the simulation of HPEM devices. While there is no conceptual limitation to develop this in 3D, our initial work has centered on 2D. The extension to 3D requires validation that the proposed fixed point iteration will converge and is the subject of our follow-up work. The eventual goal is to combine this method with particle methods for the simulations of plasma. In the current work, the scheme is evaluated for EM wave propagation within an object that is bounded by PEC. The consistency and performance of the scheme are confirmed using the ping test and frequency mode analysis for rotated square cavities—a standard test in the HPEM community. We then demonstrate the diffraction Q value test and the use of this method for simulating an A6 magnetron. The ability to handle both PEC and open boundaries in a standard device test problem, such as the A6, gives confidence on the robustness of this new method.

Nonlinear propagation of low‐frequency electromagnetic disturbances in plasmas

AbstractElectromagnetic (EM) waves/disturbances are typically the best means to understand and analyse an ionized medium like plasma. However, the propagation of EM waves with a frequency lower than the plasma frequency is prohibited by the freely moving charges of the plasma. In dense plasmas, though the plasma frequency can be typically quite high, EM sources at such higher frequency are not easily available. It is, therefore, of interest to seek possibilities wherein a low frequency (lower than the plasma frequency) EM disturbance propagates inside a plasma. This is possible in the context of magnetized plasmas. However, in order to have a magnetized plasma response in high‐density plasmas, one requires an extremely strong external magnetic field. In this manuscript, it is demonstrated that the nonlinearity of the plasma medium can aid the propagation of a slow (effective frequency lower than the plasma frequency) EM wave inside an overdense plasma. A possible mechanism of guiding, collimating, and trapping of the EM pulse or electron current pulses by appropriate tailoring of the local plasma density profile is also shown. Certain interesting applications of the propagation of such slow EM pulse through the inhomogeneous plasma is also discussed.

Design and fabrication of double layer bowtie antenna with modification of wing edge as UHF sensor for partial discharge detection in air insulation

Partial discharge (PD) has been used as a reliable diagnostic technique for High voltage equipment. UHF methods have been widely applied for the detection of electromagnetic waves emitted from PD source in High Voltage equipment. EM wave propagation produced by PD can be detected by using UHF sensors. This paper discusses the new design of double layer bowtie antenna with modification of the wing edge of the antenna as a UHF sensor for PD detection in air insulation. The double layer bowtie antenna was designed by using FR4-epoxy substrate type and later on printed on PCB. The 3D-HFSS software was used to design the bowtie antenna. Based on simulation results of double layer bowtie antenna, the optimum design for PD measurement was obtained with a minimum return loss (RL) of -34.7 dB, the bandwidth of 560 MHz, and Voltage Standing Wave Ratio (VSWR) of 1.03. Based on the measurement results for the designed bowtie antenna by using the Vector Network Analyser (VNA), the bowtie antenna has a return loss of -14 dB, the bandwidth of 555 MHz, and VSWR of 1.05. The designed UHF double layer bowtie antenna is capable of detecting PD in UHF range since PD signal have a frequency range of 300 MHz - 3 GHz.

Numerical modeling of electromagnetic-based thermal recovery techniques combined with solvent injection

Electromagnetic heating (EMH) has been the focus of ever-increasing theoretical and experimental studies to examine if it can be used to heat geomaterials at the field scale. Bitumen recovery process using EMH technique assisted by solvent injection, such as that used in Enhanced Solvent Extraction Incorporating Electromagnetic Heating (ESEIEH®) pilot in currently being conducted in the Athabasca oil sands, utilizes radiofrequency waves to generate a moderate amount of heat in the reservoir. In conjunction with dilution effect of solvent the generated thermal energy reduces the viscosity of highly viscous bitumen leading to its mobilization.Electromagnetic (EM) wave propagation in a reservoir is a coupled multiphysics process that involves not only the heat transfer and fluid flow, but also EM field distribution. Currently, a coupled approach is followed by industry using a commercial reservoir simulator (CMG-STARS) and another commercial software (ANSYS-HFSS) or in-house electromagnetic wave solver with different gridding system where both are linked through a property mapping interface (CEMRS or AxHeat). The coupled scheme utilizes the interface to map parameters from two different gridding structures which causes an additional computational load on the simulation process and could be a source of error. This study presents an alternative integrated compositional numerical modeling approach to explore the EM heating phenomena pertinent to fluid flow and heat generation and transfer in oil sand reservoirs in the same grid structure. Energy balance and EM wave propagation are derived using Maxwell's equations in the frequency domain. Then, the newly developed numerical simulator is validated using benchmark problems and used to demonstrate the physics of EM-induced volumetric heat generation in multi-phase oil sand reservoirs. Finally, the developed numerical model is applied in a case study of propane injection along the antenna to achieve oil recovery and the results are compared with the analogous Steam Assisted Gravity Drainage (SAGD).

Application of perfectly matched layers in 3D transient controlled-source electromagnetic modeling by the rapid expansion method

I have developed an extension of the rapid expansion method (REM) for 3D time-domain controlled-source electromagnetic modeling that includes perfectly matched layers (PMLs) as the absorbing boundary. The REM solves the time-domain electric field by a weighted summation of the Chebyshev polynomials. The results are free of temporal dispersion and accurate to the Nyquist frequency, yet the domain of Chebyshev polynomials lacks an accurate absorbing boundary. I find that by introducing a fictitious magnetic field in the Chebyshev domain, the recursion of the Chebyshev polynomials obeys a discrete coupled wave equation, which shares a similarity with the propagation of EM waves in a lossless medium. The time and frequency components in the Chebyshev domain are derived based on the eigenvalues of the propagation matrix, and the PML theory designed for EM waves can be extended to the Chebyshev domain in a straightforward way. Numerical tests against analytical solution and spectral methods show an excellent agreement after PML solves the boundary problem in the Chebyshev domain, which demonstrates the accuracy of the REM algorithm and the usefulness of the PML absorbing boundary.

Study on electromagnetic dynamic tunability of composite structure based on plasma periodic structure loading frequency selective surface

The plasma periodic structure has dynamic reconstruction characteristics having important practical significance in electromagnetic engineering applications. In this paper, a composite electromagnetic structure consisting of plasmas which are periodically arranged and frequency selective surface is proposed and researched. Based on the periodically arranged plasma columns, the frequency selective surface is introduced to study whether a photon-like effect will occur on EM waves propagation in the composite structure even a stronger dynamic tuning ability. The reflectivity between 1~2GHz and 8~12GHz was tested in a microwave dark room to study the influence of periodic plasma and frequency selective surface on incident electromagnetic waves with the free space method. A commercial electromagnetic software also was used to calculate the electric field at different frequency points, and study the mechanism of its interaction with electromagnetic waves.