Transmission Of Electromagnetic Signals Research Articles

The metamaterial with high thermal-mechanical stability and the practical application as the microwave antenna: Mechanical designs, theoretical predictions, and experimental demonstrations

To address the demand of maintaining the structural configuration upon extreme temperature changes, metamaterials with high thermal-mechanical stability have attracted wide attention recently. However, there are still some challenges for previous studies regarding mechanical design and practical application exploration. This manuscript proposes the design strategy for the lattice sandwich metamaterial with excellent zero thermal-induced warping, along with the metamaterial-based antenna with a high stability of electromagnetic signal transmission. Through the design strategy of discrete lattice units of the metamaterial, the ultra-low thermal warping of the metamaterial is realized upon the non-uniform temperature field. Here, the theoretical model is established to predict both heat transfer and thermal-induced deformation behavior upon complex mechanical-thermal loading conditions. The combination of theoretical predictions, finite element analysis, and experiments verifies the thermal dimensional stability of the metamaterial proposed here. Compared with the heterogeneous bilayer plate, experimental thermal warping of the metamaterial specimen is reduced by 99.7%. Additionally, compared with the bilayer-based specimen, gain attenuation, the main lobe's offset angle, and the voltage standing wave ratio offset of the metamaterial-based antenna specimen are experimentally reduced by 99.5%, 99.9% and 74.2%, revealing the huge application potential of this metamaterial in the field of spacecraft communication.

A bendable wide oblique incident angle stable polarization insensitive metamaterials absorber for visible optical wavelength applications

In the visible frequency range, the most common application is for the transmission of electromagnetic signals over air and time to an aerial receiver. They are implemented to check tapped live powered components as well as identify defects, thermal leaking hot spots, or electrical failures. This study investigates the use of a compact nonagon-shaped metamaterial absorber (MMA) for wideband visible applications by employing a three-layer substrate material structure consisting of metal, dielectric, and metal. In comparison to the most current study, the presented MMA has a smaller size, which represents a noticeable novelty. Moreover, the proposed MMA has bendable properties and two numerical simulation software have been used to validate the proposed MMA. This demonstrates the successful acquisition of data from both the CST and HFSS simulations. The proposed metamaterial absorber attained above 80% absorption in the visible ranges from 400 nm to 750 nm wavelength for the simulation mode of TE and TM, respectively. An overall unit cell size of 930 × 930 × 202 nm3 which achieves an average absorption of 95.61% in its operating band 519–677 nm for visible optical wavelength when the performance of the proposed MMA was verified using the HFSS software. Moreover, the constant absorption feature is stable over a large range of oblique incidence angles. The quality of the MMA is verified by assessing the PCR value. Wide-angle incidence angle stability, polarization insensitivity, and absorption with 15⁰ bending effects can all be observed in both modes (TM and TE). In addition, the absorption property of MMA was investigated structurally by applying electric and magnetic fields. The presented MMA can be used in wide-angle stability, MRI, color imaging, solar cells, thermal imaging, and so on.

Flexible Interdigital Sensor for Nondestructive Detecting Wear and Thickness of Tire Tread

A novel type of interdigital sensor that has been introduced in this paper can non-destructively detect the thickness of insulating materials, e.g. tire. The sensor was manufactured by jet printing technology with high efficiency. The function of the developed sensor is based on the hindering effect on the transmission of electromagnetic signals. The thickness of the insulating materials can be therefore obtained by monitoring the degree of signal reflection through transmission. For optimization, sensors made with three recipes have been experimentally tested. It is concluded that the sensor with double layers’ structure possesses the optimal performances. Practically, the application of the developed sensor in detecting the wear of tire tread has been carried out.

A Visual Human-Computer Interaction System Based on Hybrid Visual Model

The traditional human-computer interaction is mainly through the mouse, keyboard, remote control, and other peripheral equipment electromagnetic signal transmission. This paper aims to build a visual human-computer interaction system through a series of deep learning and machine vision models, so that people can achieve complete human-computer interaction only through the camera and screen. The established visual human-computer interaction system mainly includes the function modes of three basic peripherals in human-computer interaction: keyboard, mouse (X-Y position indicator), and remote control. The convex hull method was used to switch between these three modes. After issuing the mode command, Gaussian mixture was used to quickly identify the moving human body to narrow the scope of our image processing. Subsequently, finger detection in human body was realized based on the Faster-RCNN-ResNET50-FPN model structure, and realized the function of moving mouse and keyboard through the relationship between different fingers. At the same time, the recognition of human body posture was done by using MediaPipe BlazePose, and the action classification models were established through the Angle between body movements so as to realize the control function of remote control. In order to ensure the real-time performance of the interactive system, according to the characteristics of different data processing processes, CPU and GPU computing power resources are used to cross-process images to ensure the real-time performance. The recognition accuracy of the human-computer interaction system is above 0.9 for the key feature points of human body, and above 0.87 for the recognition accuracy of four kinds of command actions. It is hoped that vision-based human-computer interaction will become a widely used interaction mode in the future.

Design, dynamics, and dissipation of a torsional-magnetic spring mechanism

We present an analytical and experimental study of a torsional magnetic spring where the restoring torque results from magnetic field interactions between rotating and fixed permanent magnets (PMs). The rotating cylindrical PM, called the rotor, is supported on ball bearings between two fixed permanent magnets, called the stators. Perturbing the rotor from its equilibrium angle induces a restoring magnetic torque whose effect ressembles a torsional spring. Along with this restoring effect, dissipation mechanisms arise from structural viscoelasticity, air, electromagnetic damping, and friction in the ball bearings. To investigate dynamic effect of these restoring and dissipation mechanisms, we construct an experimental setup capable of mechanical, electrical, and magnetic measurements. For various rotor–stator gaps in this setup, we validate an analytical model that assumes viscous and dry (Coulomb) damping during the rotor’s free response. Moreover, we force the rotor by an electromagnetic coil into high amplitude oscillations. We observe unusual resonator’s nonlinearity: at large rotorstator gaps, the oscillations are softening; at reduced gaps, the oscillations stiffen-then-soften. The developed reduced-order models capture the nonlinear effects of the rotor-to-stator and the rotor-to-coil distances. These magnetic oscillators are promising for low-frequency electromagnetic signal transmission and for designing magneto-elastic metamaterials with tailorable nonlinearity.

Особенности распространения и поглощения электромагнитных сигналов в периодических структурах из проводящих и диэлектрических слоев

Different regimes of electromagnetic signal transmission through heterostructures formed by a sequence of conducting and non-conducting layers are discussed for various ratios between the frequency of radiation and the transport frequency of electron scattering in the conducting layers. Possibility to increase the efficiency of detecting or filtering electromagnetic radiation in a wide range of frequency range (from subTHz to far IR) in such structures is analyzed.

Features of propagation and absorption of electromagnetic signals in periodic structures of conducting and dielectric layers

Different regimes of electromagnetic signal transmission through heterostructures formed by a sequence of conducting and non-conducting layers are discussed for various ratios between the frequency of radiation and the transport frequency of electron scattering in the conducting layers. Possibility to increase the efficiency of detecting or filtering electromagnetic radiation in a wide range of frequency range (from subTHz to far IR) in such structures is analyzed. Keywords: propagation of electromagnetic waves in heterostructures, resonant tunneling, THz-IR detectors, bolometers.

Applicability of the ultra-high radio frequency band (UHF) for hydrometeor detection by phase difference method

Hydrometeors (rain, fog and ice crystals) affect the transmission of electromagnetic signals. Previous research showed that alterations in the signal (amplitude and phase) are affected by the composition of the atmosphere, e.g. the presence of hydrometeors. The majority of hydrometeorological detecting methods are based on the attenuation of electromagnetic signals as they penetrate the atmosphere. Novel methods based on monitoring of parameters of the signal appeared in recent time. This article presents the first results from our investigation of how hydrometeors affect the phase differences in signals transmitted by BTS stations. Cell phone operators transmit electromagnetic signals in the 1 GHz frequency band. This paper describes a novel concept of how phase differences between two signals arriving at two different antennas can be used to detect hydrometeors. Although the described concept is assumed to be independent from the signal strength, the analysed signal must be detectable. The primary advantage of the proposed passive method is that the signal is almost ubiquitous and does not require demodulation. In densely populated areas, the network of BTS stations reaches a spatial density of 1 station per 1 km2 which gives excellent opportunity to use the signal for detection purposes.

Permalloy (NiFe) nanometer square-antidot arrays: Dynamic modes and use as a monolithic microwave band-pass filter

Abstract Nanometer sized Permalloy antidot arrays with different square hole sizes have been fabricated using field emission scanning electron microscopy technique. The dynamic properties of the antidot arrays are measured at GHz frequencies using a Vector Network Analyzer. For a given applied magnetic field, we observe three resonance frequencies – one corresponds to that of a uniform mode in an infinitely extended film, and the other two (above and below this mode in frequency) correspond to modes associated with finite structures. These two modes exhibit an effective uniaxial in-plane anisotropy. The static behavior of the antidot arrays are simulated using a micromagnetic model and the electromagnetic signal transmission is analyzed using an analytical model. The results show that the three different resonance frequencies are due to the different localized shape anisotropies created by the nonmagnetic holes in the antidot array. Possible application as a magnetically tunable local band-pass filter at 5G frequency band is also studied.

Development of an Exactly Solvable Model of Resonance Tunneling of Electromagnetic Waves through Gradient Barriers in a Nonuniform Magnetoactive Plasma

An exactly solvable one-dimensional model describing resonance tunneling (reflectionless transmission) of a transverse electromagnetic wave through wide layers of magnetoactive plasma is developed on the basis of the Helmholtz equation. The plasma layers include a set of spatially localized density structures the amplitudes and thicknesses of which are such that approximate methods are inapplicable for their analysis. The profiles of the plasma density structures strongly depend on the choice of the free parameters of the problem that determine the amplitudes of plasma density modulation, characteristic scale lengths of the density structures, their number, and the total thickness of the nonuniform plasma layer. The plasma layers can also include a set of random inhomogeneities. The propagation of electromagnetic waves through such complicated plasma inhomogeneities is analyzed numerically within the proposed exactly solvable model. According to calculations, there are a wide set of inhomogeneous structures for which an electromagnetic wave incident from vacuum can propagate through the plasma layer without reflection, i.e., the complete tunneling of thick plasma barriers takes place. The model also allows one to exactly solve a one-dimensional problem on the nonlinear transillumination of a nonuniform plasma layer in the presence of cubic nonlinearity. It is important that, due to nonlinearity, the thicknesses of the evanescent plasma regions can decrease substantially and, at a sufficiently strong nonlinearity, such regions will disappear completely. The problem of resonance tunneling of electromagnetic radiation through gradient wave barriers is of interest for various applications, such as efficient heating of dense plasma by electromagnetic radiation and transmission of electromagnetic signals from a source located in the near-Earth plasma or deep in the plasma of an astrophysical object through the surrounding evanescent regions.

Fibers based on propagating bound states in the continuum

We show that a circular periodic array of $N$ dielectric cylinders supports nearly bound states in the continuum (BICs) propagating along the cylinders. These propagating nearly BICs with extremely large $Q$ factors of order $exp(\lambda N)$ are surrounded by resonant modes weakly leaking into the radiation continuum. We present leaky zones in the vicinity of different types of BICs: symmetry protected nearly BICs with the resonant width proportional to the squared propagation constant $\Gamma \sim k_z^2$, non-symmetry protected nearly BICs with finite propagation constant $k_c$ with $\Gamma\sim (k_z-k_c)^2$ and non-symmetry protected nearly BICs with $\Gamma\sim k_z^4$. The latter propagating nearly BICs can serve for transmission of electromagnetic signal paving a way to novel type of optical fibers. We also demonstrate weakly leaking resonant modes which carry orbital angular momentum.

Using broadband seismic networks to optimize microgravity survey strategy in the United Kingdom

ABSTRACTMicrogravity measurements are a useful tool for detecting subsurface features, especially deep targets or those in conductive ground which lie outside the capabilities of other methods based on electromagnetic signal transmission. However, the method is limited by a range of noise sources including vibrational noise from the environment, one source of which being the microseism noise due to ocean waves. This noise travels through the bedrock and manifests itself in the data. It varies as a function of time and location. The effect of the wave noise on microgravity measurements in the United Kingdom was assessed for the first time using a field gravimeter (Scintrex CG5) and a link was demonstrated between the noise from microgravity measurements and those from a broadband seismometer. As a result, a new method for assessing the impact of this noise on microgravity measurements in the United Kingdom is proposed using readily available data from the continuously monitoring seismic network run by the British Geological Survey to create an accurate nowcast. Knowledge of this noise on the day of survey in conjunction with an approximate signal strength of the expected targets can be used to significantly improve survey planning in terms of the optimal observation time at which surveys for particular targets should be conducted, saving time and money on failed microgravity surveys.

Theoretical Study on the While Drilling Electromagnetic Signal Transmission of Horizontal Well

Electromagnetic wave transmission is one kind of wireless signal transmission of while drilling, has been a research hotspot. The previous studies mainly on vertical well, but this technology often used in horizontal well, so it is necessary for study on the electromagnetic wave transmission from horizontal well to surface. Based on the field of the horizontal electric dipole in a conducting half-space and the equivalent transmission line theory, the theoretical model is established. Several groups of horizontal section and vertical section with different lengths are calculated. The results of calculation are analyzed.

Rain-induced attenuation for Ku-band satellite communications in the west coast of Peninsular Malaysia, Penang

Accurate rainfall rate is important for predicting rain attenuation over a satellite link. Raindrops are able to take in, spread out, and change the polarization of satellite signals that pass through the atmosphere of the earth, especially in equatorial regions like Malaysia where heavy rainfall normally occurs. Satellite communications system network operating at Ku-Band will experience rain fade due to absorption and scattering of signal. This paper aims to discuss the range of effects of rain on the transmission of electromagnetic signal and to determine the significance of rainfall rate in the prediction of rain attenuation based on measurements carried out in the northern region of Peninsular Malaysia (Penang). At 0.01% of time, 140 mm/h and 22 dB of rain rate and attenuation were observed, respectively.

Boundary Induced Inductive Delay in Transmission of Electromagnetic Signals

When an electromagnetic signal transmits through a coaxial cable, it propagates at speed determined by the dielectrics of insulator between the cooper core wire and the metallic shield. However, we demonstrate here that, once the shielding layer of the coaxial cable is cut into two parts leaving a small gap, while the copper core wire is still perfectly connected, a remarkable transmission delay immediately appears in the system. We have revealed by both computational simulation and experiments that, when the gap spacing between two parts of the shielding layer is small, this delay is mostly determined by the overall geometrical parameters of the conductive boundary which connects two parts of the cut shielding layer. A reduced analytic formula for the transmission delay related with geometrical parameters, which is based on an inductive model of the transmission system, matches well with the fitted formula of the simulated delay. This above structure is analog to the situation that an interconnect is between two inter-modules in a circuit. The results suggest that for high speed circuits and systems, parasitic inductance should be taken into full consideration, and compact conductive packaging is favorable for reducing transmission delay of inter-modules, therefore enhancing the performance of the system.

High Capacity Optical Channels for Bioinformation Transfer: Acupuncture Meridians

Mammalian bodies are hierarchical systems whose internal cooperation and coherent activity require high capacity information transfer between the central control unit – the brain – and the periphery – the organs. A communication system capable of meeting information capacity requirements should be based on transmission of electromagnetic signals. Structures that fulfill requirements for such information transfer have not yet been analyzed. Acupuncture meridians have been demonstrated experimentally in some animals. They might represent systems of information transfer between the brain and the peripheral organs. The ducts of the meridians may correspond to optical fibers operating from the far infrared to the visible wavelength region. The main features of a model of the duct as an optical fiber are delineated and its properties outlined. However, to analyze essentials of the transmission capabilities, the whole meridian structure should be mapped and a more comprehensive set of physical parameters measured. In particular, experimental data concerning morphological arrangements of ordered water in the ducts and corpuscles, and a complete content of the biological particles in the flowing water and its permittivity are missing.

Hearing aid with antenna for reception and transmission of electromagnetic signals

The invention regards a communication device which is adapted for placement in a users ear. The communication device comprises a shell part enclosing an input transducer for receiving an input signal, a signal processing device and an output N transducer for providing a signal perceivable as sound, a battery located at a surface part of the shell which is facing away from the head of the user, a transmission and reception circuit for transmission and/or reception of electromagnetic energy. According to the invention an antenna for radiating and/or receiving electromagnetic energy is provided such that it has a first surface turned towards the surroundings and a second surface located in close proximity of the battery.

Development and clinical testing of a non-magnetic cochlear implant. Preliminary experimental studies and surgical concept. Results in the first 10 patients

To ensure good transmission of electromagnetic signals from the speech processor to the internal cochlear stimulator (ICS) in cochlear implants, exact alignment of the external transmitter coil over the receiver coil of the ICS is necessary. Usually this is achieved by two magnets: one implanted within the ICS, the other one integrated into the transmitter coil of the external headset. Although this principle works, there are some serious problems with the implanted magnet. The most serious of these is that it renders MRI studies potentially hazardous or impossible, or at least compromises image quality. We developed a method to eliminate the magnet. The method requires varying the implantation technique and using a special headset. The technique is easy to perform, and the headset is suitable for series production. Experience with our first patients revealed the coil alignment to be remarkably stable, even more than in patients with a cochlear implant equipped with a magnet. Results of the first ten patients are presented. Aside from eliminating the magnet, we attempted to optimize the acoustic properties of the headset. This resulted in design changes such as repositioning the microphone. Further improvements such as integration of telephone coils and special sockets to connect peripheral appliances can easily be implemented in our special headset.

Balloon measurements above the south pole: Study of ionospheric transmission of ULF waves

We report here an experimental study of the Hughes and Southwood model of the transmission of electromagnetic signals from the ionosphere/magnetosphere to the lower atmosphere. The electric field data were obtained from one of eight high‐latitude balloon payloads launched above the south geographic pole during the South Pole Balloon Campaign in the 1985–1986 austral summer. The magnetic field data are from the South Pole magnetometer. The balloon payloads were instrumented with double‐probe electric field detectors and bremsstrahlung X ray detectors. One of the events from flight 7 (January 8, 1986, at 1500–1800 UT (1130–1430 MLT)) had an amplitude in the range of 10–20 mV/m and a period of several minutes. In the magnetosphere, the wave was probably an Alfvén mode. The wave event was superimposed on background fluctuations that can be attributed to turbulence. The results agree with the predictions of the model in that the best coherence is observed between parallel components of E versus B. The results disagree with the predictions of the model in two respects. First, we find a frequency structure not predicted by the model, and second, we find intervals where the electric and magnetic field polarizations are of opposite handedness. The first discrepancy was modeled by taking account of the measured electrostatic turbulence. The second problem remains a puzzle.

Aerosol spectral optical depths: Jet fuel and forest fire smokes

The Ames autotracking airborne sun photometer was used to investigate the spectral optical depth between 380 and 1020 nm of smokes from a jet fuel pool fire and a forest fire in May and August 1988, respectively. Results show that the forest fire smoke exhibited a stronger wavelength dependence of optical depths than did the jet fuel fire smoke at optical depths less than unity. At optical depths greater than or equal to 1, both smokes showed neutral wavelength dependence, similar to that of an optically thin stratus deck. These results verify findings of earlier investigations and have implications both on the climatic impact of large‐scale smokes and on the wavelength‐dependent transmission of electromagnetic signals.