Frequency Electromagnetic Waves Research Articles

Evaluating numerous techniques for the effects of electromagnetic waves on the Electro Cardio Gram (ECG)

<p>Nowadays, due to the widespread use of mobile phones and the proliferation of mobile towers the human body parts especially the heart are getting affected. Furthermore, these waves are ubiquitous in our modern society, with various sources emitting these waves in our environment. As medical devices become more prevalent and wireless technologies continue to advance, concerns have been raised regarding the potential impact of electromagnetic waves on human health. It is important to monitor the condition of your heart. With the increase in the number of mobile phones, there is also an increase in electromagnetic radiation, which can affect the human heart. The heart is an important component of the human body and an electrocardiogram (ECG) can provide valuable information about its condition. ECG parameters can show how well the heart is working. In this paper, the author proposes how ECG parameters change under the influence of mobile phones in three different situations. A comprehensive experimental setup was devised. A group of healthy human subjects volunteered to participate in the study, with each subject undergoing ECG recording under controlled conditions. The subjects were exposed to varying intensities and frequencies of electromagnetic waves generated by a standardized source. Statistical analysis was performed to compare the ECG measurements obtained during exposure to electromagnetic waves with those obtained in a controlled environment without electromagnetic wave exposure. This study contributes to the growing body of research on the potential health effects of electromagnetic waves. By specifically focusing on the ECG signal, which is vital for cardiovascular diagnostics, this research provides valuable insights into the safety and reliability of using ECG in environments with electromagnetic wave exposure. The findings will help inform healthcare professionals, engineers, and policymakers to establish appropriate guidelines and safety measures concerning the use of medical devices and wireless technologies in proximity to patients or individuals with cardiac conditions.</p>

Wireless electromagnetic telemetry for metal cased wells: A novel approach with comprehensive channel analysis

Low-frequency electromagnetic telemetry has been widely adopted for downhole data acquisition in the oil and gas industry. However, its application in cased wells has been limited by the high magnetic permeability and low resistivity of the metal casing, which causes the casing to absorb most of the electromagnetic waves transmitted by the downhole transmitter, resulting in inaccurate downhole data acquisition. We propose a novel approach to address this issue by suspending a transmitter (tens of meters in length) in the casing and connecting it electrically to the metal casing through two connectors. By forming a circulation along the transmitter and the casing, low-frequency electromagnetic waves can penetrate through the casing and reach the formation for telemetry. To further enhance the signal received by the ground antenna, we conduct a comprehensive analysis of the complex downhole-to-surface communication channel. Notably, the channel, which consists of the formation, the casing, and the transmitter, is divided into a near field and a far field for separate analysis. Quantitative assessments of four crucial factors on the ground-received signal strength are also conducted, i.e., electromagnetic wave frequency and location of the excitation source in the transmitter, as well as the length and location of the transmitter in the well. An 80-meter telemetry device is designed and optimized for integration into the well test. Experimental results confirm the consistency between the theoretically analyzed and measured attenuation law of the ground-received signal, indicating the effectiveness of our wireless electromagnetic telemetry technique for cased wells.

A Dual Neural Network Approach to Topology Optimization for Thermal-Electromagnetic Device Design

Topology optimization for engineering problems often requires multiphysics (dual objective functions) and multi-timescale considerations to be coupled with manufacturing constraints across a range of target values. We present a dual neural network approach to topology optimization to optimize a 3-dimensional thermal-electromagnetic device (optical shutter) for maximum temperature rise across a range of extinction ratios while also considering manufacturing tolerances. One neural network performs the topology optimization, allocating material to each sub-pixel within a repeating unit cell. The size of each sub-pixel is selected with manufacturing considerations in mind. The other neural network is trained to predict performance of the device using extinction ratio and temperature rise over a given time period. Training data is generated using a finite element model for both the electromagnetic wave frequency domain and thermal time domain problems. Optimized designs across a range of targets are shown.

Simulation of filamentation dynamics of microwave discharge in nitrogen

The present study deals with numerical simulations of microwave (MW) discharges in nitrogen based on extended fluid-dynamic model. The set of governing equations for non-equilibrium gas-discharge plasma includes conservation equations for species number densities, electron energy density, Poisson equation for the electric field coupled to the multi-temperature Navier–Stokes fluid-dynamic equations taking into account thermal nonequilibrium; the power transmitted from MW radiation to electrons is determined from the Helmholtz equation. The kinetic scheme includes 61 reactions involving neutral molecules and atoms in the ground and electronically excited states, ions and electrons. The set of equations is solved for a two-dimensional problem under conditions of experiments at a pressure of 40 and 50 Torr and different electromagnetic wave frequencies and pulse duration. The dynamics of discharge formation and transition from the diffuse to the filament form is studied. The results are compared with experimental data, and a good agreement is shown for the time larger than 10 µs. The possible reasons for discrepancies at a shorter time are discussed and the effect of small oxygen impurities on the quantitative characteristics of the discharge are evaluated. The presence of a small oxygen impurity and seed electrons in the region of discharge formation yields a better agreement between numerical and experimental data.

Study on the propagation properties of terahertz waves in spacecraft dusty plasma sheath

Terahertz (THz) wave transmission in non-uniform dielectric layer containing dusty plasmas and aluminum (Al) is investigated by using the Wentzel–Kramer–Brillouin method. The application of magnetic field and increase in electromagnetic waves frequency are up-and-coming solutions for the “blackout” issue. Therefore, this work considers the effect of external magnetic field and electron density distribution. The electron density distributions are assumed to be double Gaussian profile, uniform distribution, Epstein distribution, and both right- and left-hand circularly polarized waves are analyzed. Then the effects of physical parameters and THz frequency on the transmission properties are analyzed. Results show that the presence of Al can shield electromagnetic waves, but we can still control THz waves in lower frequency band to achieve communication. By adjusting THz waves frequency and plasma parameters, waves can pass through the Al plasma sheath effectively under certain circumstances. It is expected to mitigate the blackout issue of hypersonic spacecraft.

Initial Finite-Difference Time-Domain (FDTD) Modeling of Graphene Based on Intra-band Surface Conductivity

Graphene is a single two-dimensional layer of carbon atoms arranged in a hexagonal lattice, possesses interesting optical properties, and has potential for applications in optical devices. Graphene exhibits tunable surface conductivity, which arises from its electronic band structure. Graphene surface conductivity is determined by its chemical potential, which can be controlled by bias voltage and/or chemical doping. The tunability of surface conductivity allowed to tailored optical properties of graphene, making it a controllable material for optoelectronic applications. Graphene surface conductivity is applied to update the field values at each time step in the Finite-Difference Time-Domain (FDTD) method, enabling us to visualize electromagnetic (EM) wave propagation in graphene. The current article serves as a starting point for developing the FDTD approach to simulate EM wave interactions with graphene, particularly at low frequencies. In this study, we use the Kubo formula for low EM wave frequency (10-105 GHz) at ambient temperature to calculate the intra-band surface conductivity of graphene. The outcome shows that the imaginer’s intra-band surface conductivity value is relatively considerable compared to the actual value at frequencies between 102 and 104. Moreover, the chemical potential exhibits a positive linear relationship with the imaginer intra-band surface conductivity and the intra-band conductivity falls to zero as the frequency rises to NIR.

Unlocking the Power of Reconfigurable Intelligent Surfaces: From Wireless Communication to Energy Efficiency and Beyond

Reconfigurable Intelligent Surfaces (RISs) are a class of metamaterials that have gained significant attention in recent years due to their potential to revolutionize wireless communication, sensing, and imaging technologies. RISs consist of a planar array of closely spaced, subwavelengthsized elements that can manipulate electromagnetic waves in a controllable manner. By reconfiguring the geometry, material properties, or phases of the individual elements on the RIS, the surface can be customized to meet specific application requirements. RISs can improve wireless communication by creating virtual channels, reducing interference, and improving overall quality. They can also enhance the efficiency of energy harvesting systems and improve sensing and imaging technologies by manipulating the propagation and scattering of electromagnetic waves. Additionally, RISs could be used to increase privacy and security by selectively blocking or allowing specific frequencies of electromagnetic waves. In this editorial, we provide a brief history of the development of RISs and discuss the design and fabrication of RIS structures. We also discuss RIS technology’s potential applications and benefits, including improved wireless communication, enhanced energy efficiency, advanced sensing and imaging, and increased privacy and security. Finally, we highlight some current research challenges and future directions for RIS technology. Overall, RISs hold great promise for advancing a wide range of technologies and applications, and we expect to see many exciting developments in this area.

Dispersion-boosting wideband electromagnetic transparency under extreme angles for TE-polarized waves.

Half-wave wall is the most common method of achieving electromagnetic (EM) transparency. Transmission windows can be formed when reflected waves are out of phase. Due to the interference mechanism, these windows are dependent on the frequency and incident angle of EM waves, leading to limited bandwidth, especially under extreme angles. In this letter, we propose to extend the bandwidth of the transmission window under extreme angles by utilizing dispersion. To this end, long metallic wires are embedded into the half-wave wall matrix, without increasing the physical thickness. Due to the plasma-like behavior of metallic wires under TE-polarization, the effective permittivity of the half-wave wall, rather than keeping constant, increases with frequency nonlinearly. Such a dispersion will boost wideband transparency in two aspects. On one hand, an additional transmission window will be generated where the effective permittivity equals that of the air; on the other hand, the 1st- and 2nd-order half-wave windows will be made quite closer. By tailoring the dispersion, the three windows can be merged to enable wideband transparency under extreme incident angles. A proof-of-principle prototype was designed, fabricated, and measured to verify this strategy. Both simulated and measured results show that the prototype can operate in the whole Ku-band under incident angle [70°, 85°] for TE-polarized waves. This work provides an effective method of achieving wideband EM transparency under extreme angles and may find applications in radar, communications, and others.

COMPARATIVE ANALYSIS OF EMBROIDERY AND SCREEN-PRINTING TECHNIQUES FOR TEXTILE-BASED FREQUENCY SELECTIVE SURFACES

Frequency Selective Surface (FSS) is a specialized structure used in the field of electromagnetic waves and radio frequency (RF) engineering. It is designed to exhibit selective transmission or reflection properties based on the frequency of the incident electromagnetic waves. This article describes the design, construction, and analysis of a textile-based band-stop frequency selective surface for use in the highly EM-polluted GSM, Wi-Fi, LTE, and WiMAX bands. A full-wave EM solver called CST Microwave Studio was used to develop and simulate the unit cell of the proposed FSS at the relevant frequency. In this study, embroidered and screen-printed textile based FSSs were designed. According to the results of this study, it was demonstrated that both embroidery and screen printing FSSs exhibit resonance at a frequency of 3.5 GHz. The screen printing method yielded the best results in terms of resonance frequency sensitivity, while the embroidery method showed a resonance frequency shift. It was observed that the stitch directions and density are important parameters in the embroidery method. Gaps between the embroidery paths in the production of embroidered FSSs resulted in differences from simulations due to the disruption of the structural integrity of the unit cell. Consequently, textile-based FSSs offer advantages over traditional FSSs. This study highlights the potential of textile FSSs as an effective means of reducing electromagnetic pollution, and suggests that further improvements in the design and production processes of textile FSSs can be made.

Electromagnetic field detectors based on spintronics devices

The paper proposes a model of an electromagnetic radiation sensor that uses the precession of the magnetization vector in a ferromagnet (ferromagnetic resonance) as a result of absorbing the energy of an incident electromagnetic wave, the generation of a spin current as a result of this precession, the generation of a spin-polarized current as a result of the passage of a spin current in a non-magnetic metal, and a change in the direction of magnetization of a ferromagnetic layer with a low coercive force (free layer) due to the passage of a spin-polarized current. Then the radiation will be detected by its effect on the electrical resistance of the entire structure, which depends on the mutual directions (parallel or antiparallel) of magnetization of the free and fixed (with a large coercive force) ferromagnetic layers (phenomenon of giant magnetic resistance). The dependence of the spin-polarized current in the device on the frequency and amplitude of the incident electromagnetic wave with linear polarization was calculated. A method of calculating the range of amplitude and frequency values of radiation that can be detected by the sensor has been developed. The parameters of this model are the detection time and the number of spin gates in one sensor. Calculations are given for a ferromagnetic layer made of permalloy and for spin valves with four different critical current values that determine the process of remagnetization of the free layer: 20, 50, 100, and 200 microamps.

Fusion of electromagnetic world and digital world through information metasurface: an interview with Tie Jun Cui.

Metasurfaces consist of subwavelength artificial elements (also called meta-atoms) arranged in a two-dimensional fashion. Through careful design of these elements, the metasurfaces can control the amplitude, phase, frequency, and polarization of electromagnetic (EM) waves. Information metasurfaces extend this concept by characterizing the meta-atoms in a digital manner, integrating functionalities for information processing. The information metasurfaces can simultaneously manipulate the EM waves in reprogrammable ways and modulate the digital information in real time, making the fusion of the EM world and digital world. The information metasurfaces have found diverse applications in wireless communications, intelligent sensing and imaging, intelligent computing, and internet of things (IoT). Prof. Tie Jun Cui is affiliated with Southeast University in Nanjing, China, where he serves as the Director of the State Key Laboratory of Millimeter Waves. He is a prominent researcher in the field of metamaterial, metasurface, and computational electromagnetics. He has proposed the concepts, and made systematic studies, of digital coding metasurfaces and programmable metasurfaces, and established the system of information metasurfaces, building a direct link between the electromagnetic world and digital world. NSR spoke to Professor Cui on the recent advancement and the prospects of information metasurfaces.

Research on Channel Characteristics and Electrode Electrical Performance of Earth Current Field Information Transmission Technology.

Starting from the need for emergency rescue information transmission in tunnel engineering accidents, this article focuses on researching and solving the technical problems of information transmission between rescue personnel and trapped personnel after tunnel engineering collapse accidents, before and during the rescue process. The research objects are the information transmission channel and grounding electrode in the earth current field information transmission technology, and the electromagnetic characteristics of the earth medium and the electrical performance of the grounding electrode are studied and analyzed using the electromagnetic simulation software Maxwell based on finite element algorithm, establish a three-dimensional model based on the transmission of current field information of the ground electrode, analyze the effects of the electrode array, electrode depth, and radius on impedance. Research has shown that the impedance of the earth is related to the resistivity of the medium and is not a human-controllable factor. To reduce the contact impedance of an electric dipole antenna, one should start with the contact impedance of the earth electrode. The impedance of the transmitting end is an important factor affecting the efficiency of information transmission; parallel connection of multiple grounding electrodes, increasing the depth of grounding electrode penetration into the soil layer, and increasing the radius between grounding electrode pairs are all effective methods to reduce the contact impedance of electric dipole antennas, thereby improving information transmission capacity. To achieve wireless information transmission through the stratum, by appropriately selecting the operating frequency of electromagnetic waves, a certain distance of signal transmission can be achieved.

Influences of spatial structure of plasma shock wave on electromagnetic wave propagation characteristics

Plasma shock waves represent high-speed, nonlinear motion states of plasma in which the physical parameters of fluid, such as density, temperature, and velocity, vary dramatically within a limited space. These variations make studying electromagnetic wave propagation in plasma shock waves difficult. In this study, we calculate the spatial distribution of the plasma frequency and collision frequency in the plasma shock layer based on the one-dimensional structure of the plasma shock wave. In the process from upstream to downstream of the plasma shock wave, the plasma frequency increases as a function of electron density; downstream, the plasma frequency increases as a function of the free stream Mach number, while the collision frequency decreases first and then increases. We also use the recursive convolution finite-difference time-domain method to calculate the propagation of the electromagnetic wave in the plasma shock layer. The absorption of the plasma shock layer to the electromagnetic wave decreases gradually as a function of the electromagnetic wave frequency. The absorption of the plasma shock layer downstream of the electromagnetic wave is greater than that upstream owing to the larger plasma frequency. In the case of low-Mach numbers, the wavelength of the electromagnetic wave downstream is larger than that upstream. In the case of high-Mach numbers, the thickness of the entire shock layer is much greater than that at low-Mach numbers. Due to the nonlinear effects of electromagnetic processes in plasmas, a modulation phenomenon occurs when electromagnetic waves propagate in the shock layer. In the case of low frequencies, the electromagnetic wave gave rise to a modulation phenomenon that resembled the beat phenomenon. When the electromagnetic wave frequency increased, a modulation phenomenon gradually appeared that resembled the oscillation superimposed on a sine wave. Further increases in the electromagnetic wave frequency led to the gradual disappearance of the modulation phenomenon.

Modulation of electromagnetic waves in a relativistic degenerate plasma at finite temperature

We study the modulational instability (MI) of a linearly polarized electromagnetic (EM) wave envelope in an intermediate regime of relativistic degenerate plasmas at a finite temperature (T≠0) where the thermal energy (KBT) and the rest-mass energy (mec2) of electrons do not differ significantly, i.e., βe≡KBT/mec2≲ (or ≳) 1, but the Fermi energy (KBTF) and the chemical potential energy (μe) of electrons are still a bit higher than the thermal energy, i.e., TF>T and ξe=μe/KBT≳1. Starting from a set of relativistic fluid equations for degenerate electrons at finite temperature, coupled to the EM wave equation and using the multiple scale perturbation expansion scheme, a one-dimensional nonlinear Schödinger (NLS) equation is derived, which describes the evolution of slowly varying amplitudes of EM wave envelopes. Then, we study the MI of the latter in two different regimes, namely, βe<1 and βe>1. Like unmagnetized classical cold plasmas, the modulated EM envelope is always unstable in the region βe>4. However, for βe≲1 and 1<βe<4, the wave can be stable or unstable depending on the values of the EM wave frequency, ω, and the parameter ξe. We also obtain the instability growth rate for the modulated wave and find a significant reduction by increasing the values of either βe or ξe. Finally, we present the profiles of the traveling EM waves in the form of bright (envelope pulses) and dark (voids) solitons, as well as the profiles (other than traveling waves) of the Kuznetsov–Ma breather, the Akhmediev breather, and the Peregrine solitons as EM rogue (freak) waves, and discuss their characteristics in the regimes of βe≲1 and βe>1.

Molecularly Resonant Metamaterials for Broad-Band Electromagnetic Stealth.

Electromagnetic (EM) metamaterial is a composite material with EMstealth properties, which is constructed by artificially reverse engineering metal split resonance rings (SRR). However, the greatest limitation of EM metamaterials is that they can only stealth at a fixed and lower frequency of EM waves, and modern processing techniques still cannot meet the accuracy requirements to fabric nano-size structural unit. Nano-sized and even ultra-small SRR at molecular level are promising arrays to realize the ability of EM stealth function at a higher frequency, although it has proven challenging to synthesize long, straight, connected molecular SRR, and also difficult to arrange those molecular SRR into a strict array. Here, the study overcomes this challenge and demonstrates that the fabric of polypyrrolemolecular SRR achieves an ultra-small inner diameter of 2.49 Å and realizes the arrays arrangement at molecular level. Furthermore, the study exploits the EM stealth function and verifies that such arrays of molecular SRR with 2.49 Å have the ability to reach high-performance EM stealth in the range of 106 -1016 Hz. This design concept opens a pathway for developing new metamaterials with broadband EM wave stealth and also serves the wider range of new applications.

Perspective on active submillimeter electromagnetic wave imaging using CMOS integrated circuits technologies

The performance of CMOS transmitters and receivers operating at the submillimeter electromagnetic wave frequencies have sufficiently improved for use in active transmission and reflection-mode imaging applications that have the potential for broad deployment and utilization. Imaging integrated circuits have the potential to be large in area to support a high number of pixels along with digital backend processing circuits. For high volume imaging applications that may eventually be included in automobiles, smartphones, laptops, tablets, and others, a large manufacturing capacity to support the volume of large area ICs is necessary. For this, the use of CMOS technologies with a much larger manufacturing capacity is favored. It should be possible to improve the performance of CMOS circuits to increase the range, and operation margin and frequency. The electronically steerable submillimeter-wave reflector technology holds the promise for improving the performance and energy efficiency of submillimeter-wave imaging systems by multiple orders of magnitude, and it is a critical research area. Increasing the operating frequency from 430 to 850 GHz using CMOS integrated circuits to improve the angular resolution by 2X at a given form factor (∼0.15° for a reflector diameter of 15 cm) can make the submillimeter-wave imaging competitive to the LIDAR angular-resolution performance, while providing superior capabilities in visually impaired conditions and making the imaging devices more affordable.

Design and Preparation of Flexible Graphene/Nonwoven Composites with Simultaneous Broadband Absorption and Stable Properties

As the world moves into the 21st century, the complex electromagnetic wave environment is receiving widespread attention due to its impact on human health, suggesting the critical importance of wearable absorbing materials. In this paper, graphene nonwoven (RGO/NW) composites were prepared by diffusely distributing graphene sheets in a polypropylene three-dimensional framework through Hummers' method. Moreover, based on the Jaumann structural material design concept, the RGO/NW composite was designed as a multilayer microwave absorber, with self-recovery capability. It achieves effective absorption (reflection loss of -10 dB) in the 2~18 GHz electromagnetic wave frequency domain, exhibiting a larger bandwidth than that reported in the literature for absorbers of equivalent thickness. In addition, the rationally designed three-layer sample has an electromagnetic wave absorption of over 97% (reflection loss of -15 dB) of the bandwidth over 14 GHz. In addition, due to the physical and chemical stability of graphene and the deformation recovery ability of nonwoven fabric, the absorber also shows good deformation recovery ability and stable absorption performance. This broadband absorption and extreme environmental adaptability make this flexible absorber promising for various applications, especially for personnel wearable devices.

High-performance transparent electromagnetic interference shielding film based on metal meshes

Transparent electromagnetic interference (EMI) shielding films have gained considerable attention for the commercialization of the 5G wireless technology based on electromagnetic waves in the GHz range. In this study, transparent EMI shielding films with embedded metal meshes on a 100 μm thick polyethylene terephthalate film for EMI shielding were fabricated using ultraviolet imprinting and Ag paste filling techniques. The various EMI shielding film types were fabricated by varying the width, aperture size, and height of the mesh electrode to evaluate the efficiency of the EMI shielding according to the incident electromagnetic wave frequency and morphology of the mesh metallic electrodes. The results indicate that the EMI shielding efficiency (SE) increased with a decrease in the aperture size of the metal mesh electrodes and an increase in their height. The average EMI SE values of the fabricated film in the 0.5–18 GHz range reached 48.3 dB and 59.6 dB at a light transmittance of approximately 90% and 77%, respectively. The fabricated EMI shielding films can be used for various applications, such as communications, aerospace, medical equipment, and military.

Design of the Polarization-Independent Wavelength Multiplexing Holographic Metasurface

Metasurface regulates the polarization, phase, amplitude, frequency, and other characteristics of electromagnetic waves through the subwavelength microstructure. By using its polarization characteristics, it can realize the functions of optical rotation and vector beam generation. It is the most widely used method of regulation. However, parallel optical manipulation, imaging, and communication usually require polarization-insensitive focused (or vortex) arrays of beams, so polarization-independent wavelength multiplexing optical systems need to be considered. In this paper, the genetic algorithm combined with the computer-generated hologram (CGH) is used to control the transmission phase of the structure itself, and on the basis of wavelength multiplexing, the corresponding array of focused or vortex beams without the polarization selection property is realized. The simulation software results show that the method has a huge application prospect in optical communication and optical manipulation.

Analysis and weakening of radial electromagnetic forces in high‐speed permanent magnet motors with external rotors based on shape functions

AbstractIn this paper, a strategy of integrating direct‐drive turbine compressors with high‐speed permanent magnet external rotor motors is used to improve the problems of large footprint, low efficiency and high maintenance costs. The rotor of the motor will vibrate under the action of radial electromagnetic force when rotating, and under the action of high pressure and high speed gas, it may aggravate the rotor vibration. In the case of changing the original mechanical structure of the turbine, the vibration of the motor rotor needs to be analysed. In the paper, the radial electromagnetic force applied to the rotor is analysed. The influence of the order and size of the stator and rotor magnetic field harmonics on the size, frequency and order of the radial electromagnetic force wave is summarised. In order to weaken the radial electromagnetic force, this paper proposes a shape function about the magnetic pole size and designs a magnetic pole accordingly. The validity of the shape function was confirmed by comparing the radial electromagnetic force wave with a conventional, surface‐mounted, built‐in magnetic pole structure. Finally, based on the analysis of the rotor dynamics mode, the law of the effect of the change of the pole arc coefficient of the pole on the radial force was analysed using harmonic response, and reasonable conclusions were drawn.