Propagation Of Electromagnetic Signals Research Articles

Coherent suppression of electromagnetic dissipation due to superconducting quasiparticles.

Owing to the low-loss propagation of electromagnetic signals in superconductors, Josephson junctions constitute ideal building blocks for quantum memories, amplifiers, detectors and high-speed processing units, operating over a wide band of microwave frequencies. Nevertheless, although transport in superconducting wires is perfectly lossless for direct current, transport of radio-frequency signals can be dissipative in the presence of quasiparticle excitations above the superconducting gap. Moreover, the exact mechanism of this dissipation in Josephson junctions has never been fully resolved experimentally. In particular, Josephson's key theoretical prediction that quasiparticle dissipation should vanish in transport through a junction when the phase difference across the junction is π (ref. 2) has never been observed. This subtle effect can be understood as resulting from the destructive interference of two separate dissipative channels involving electron-like and hole-like quasiparticles. Here we report the experimental observation of this quantum coherent suppression of quasiparticle dissipation across a Josephson junction. As the average phase bias across the junction is swept through π, we measure an increase of more than one order of magnitude in the energy relaxation time of a superconducting artificial atom. This striking suppression of dissipation, despite the presence of lossy quasiparticle excitations above the superconducting gap, provides a powerful tool for minimizing decoherence in quantum electronic systems and could be directly exploited in quantum information experiments with superconducting quantum bits.

Analysis of Ground-Based Navigation Signal Coverage on Performance-Based Navigation

The implementation of PBN is an important part of China's civil aviation to enhance national strength program,the evaluation of the ground-based navigation signal Overlay is an essential part of the design of flight procedures.This article start from the principle of electromagnetic wave propagation in the atmosphere and establish a reasonable mathematical model for the propagation of electromagnetic signals,then make use of the secondary development for ArcGIS to complete the evaluation system of Ground-based navigation signal overlay while considering the requirements of DME / DEM update area for 2 DME station.

Propagation of electromagnetic signals in the time-varying plasma

Because the boundary layer of the plasma sheath formed around the hypersonic vehicle flying in atmosphere is turbulent, the parameters of plasma sheath, such as the electron density, become time-varying. Both the amplitude and phase of electromagnetic (EM) signal are modulated by the time-varying plasma. By using a large volume uniform plasma generator, an experimental system for the propagation of EM signals in the time-varying plasma is built. The propagation experiment of the monochromatic signals and binary phase shift keying signals in S band of plasma is conducted. The modulations of the amplitude and phase of EM signal are proved, and the rotation of constellation of the multiple phase shift keying (MPSK) signal is observed. The experimental and simulation results demonstrate that the frequency of parasitic modulation is the same as that of time-varying plasma and the parasitical modulation intensity varies in proportion to the ratio of the electron density profile to the carrier frequency. Even if the carrier frequency is higher than the plasma frequency, the parasitical modulation will make the constellation of the MPSK signals circumvolve, and the bit error rate higher.

Power Cable Fault Locator Based on Synchronization Principle of Sound and Magnetic

The synchronization method based on the sound and magnetic makes power cable precise positioning more intuitive in this paper,which based on the pre-positioning of the cable fault an accurate fault location method.First the pulse generator discharges pulse applied to the cable, the fault point will release the sound signal and an electromagnetic signal. But the electromagnetic signal propagation speeds approaching the speed of light instantaneously reaches the point of failure.when the electromagnetic signal is detected , the microcontroller timer T1 is informed. T1 starts counting until up to the sound signal is detected. the LCD will display the counting result, and along the cable to we will find the minimum point of the time value ,which is the location of the fault point.

Multiparameter seismo-ionospheric anomaly observation before the 2008 Wenchuan, China, Mw7.9 earthquake

The atmosphere-ionosphere response before 2008 Mw7.9 Wenchuan earthquake based on global positioning system (GPS), detection of electro-magnetic emission transmitted from earthquake regions (DEMETER), and National Oceanic and Atmospheric Administration—advanced very high resolution radiometer (NOAA/AVHRR) satellite data is analyzed. It is found that GPS total electron content (TEC) above the epicenter continuously decreased in the afternoon periods from 6 to 10 May but increased in the afternoon of 9 May. Contour analysis on ionospheric plasma using Instrument Sonde de Langmuir data onboard DEMETER satellite showed that electron density (Ne) and ion density (Ni) was also reduced from 6 to 10 May, the anomalous region mainly distributed in the south of the epicenter, conforming to the anomalous TEC area. The brightness temperature (T b ) from NOAA/AVHRR data, calculated by K index method, shows a noticeable enhancement on the northwest side of the epicenter on 7 May, while ion temperature (T i ) from DEMETER data increased on 9 May with the order of ∼12.5% . The energetic particle flux presents an obvious enhancement for the spectrum at 100 to 600 keV energy range on 6 May. Preliminary study suggests the perturbations of these parameters (TEC, Ne, Ni, T b , and T i ) before the Wenchuan earthquake may be related to the changes of vertical electric field in the atmosphere and ionosphere, induced by the enhancement of stress in tectonic regions and the electromagnetic signal propagation from the earthquake preparation area.

Spectral Downscaling of Integrated Water Vapor Fields From Satellite Infrared Observations

Atmospheric water vapor is a crucial constituent affecting both climate change and hydrological cycle processes, whereas on the other hand, it has a significant impact on the electromagnetic signal propagation. Since the distribution of atmospheric water vapor strongly varies with time, location, and altitude, it is necessary to monitor it at high spatial and temporal resolution. Unfortunately, mapping its spatial distribution is difficult due to the lack of meteorological instrumentation at an adequate spatial and temporal observation scale. For many geophysical applications, there is also the need to reconstruct spatial details of integrated precipitable water vapor from information available only at coarser spatial scales. Spatial downscaling approaches can play a significant role when high-resolution water vapor retrievals from relatively new sensors, like synthetic aperture radars, or from conventional sensors, like the infrared radiometers MEdium Resolution Imaging Spectrometer (MERIS) or Moderate Resolution Imaging Spectroradiometer (MODIS), are used in synergy to enhance the accuracy of integrated water vapor retrievals. In this context, this paper introduces some new methodological aspects to increase the spatial resolution of integrated precipitable water vapor observations using a statistical downscaling spectral approach. To highlight the potential and the usefulness of the proposed downscaling estimation procedure, collocated 250-m MERIS and 1-km MODIS acquisitions are used. Results reveal the ability of spectral downscaling to reproduce quite well the second-order statistical variability of the water vapor field at small spatial scales with a root-mean-square error comparable with conventional interpolation techniques.

Estimation of the strike angle of an empty tunnel in different rocks using a cross‐borehole pulse radar

The finite difference time domain method is employed to calculate the radar signatures of an obliquely penetrating tunnel in various background media. The relatively faster propagation of electromagnetic signal and stronger distortion in the first peak were discovered due to the existence of an empty tunnel as its penetration angle becomes more oblique. It renders the arrival time of the first peak to be increased relatively slower than that of the first received signal. To analyze the different behaviors of two arrival times, those data are compared with the straight line model and the ray‐tracing model. Finally, the relation between the penetration angle of an empty tunnel and the arrival time of received pulse signatures is evaluated with the curve fitting model in three different background media. These results are compared with the measured data in a well suited tunnel test site.

Electromagnetic wave propagation in inhomogeneous, moving media: A general solution of the problem

The exact computation, the exact modeling of the propagation of electromagnetic signals through inhomogeneous moving media, is an old theoretical and measuring/data interpretation problem, because in a lot of practical problems, such as the accurate space‐time determination in satellite positioning systems, the occultation measurements, or the accurate tracking of the interplanetary probes, the electromagnetic wave (signal) traverses moving, inhomogeneous media, where the moving velocity of the media and the media itself are inhomogeneous in space, i.e., the Earth's high and low atmosphere, the planetary atmospheres, the interplanetary matter in the inner and outer solar system, etc. In other important cases of electromagnetic wave propagation, as the propagation in inhomogeneous media or the propagation of short impulses (ultrawide‐band (UWB) signals), the application of the method of inhomogeneous basic modes (MIBM) was successful. In this paper it is demonstrated that the application of MIBM in the case of inhomogeneous moving media produces an exact, full‐wave solution of monochromatic or UWB signals propagating through these media. The solutions are valid inside the special relativity.

Copper Metallization for Current Very Large Scale Integration

As silicon technology scaling progresses to the 32 nm node or even further, the design on the propagation of electromagnetic signals becomes increasingly appealing due to their unyielding constraints on interconnect delay. Because of its high conductivity and electromigration resistance, Cu is now the interconnect materials in current VLSI. To ensure the signal propagation via the Cu interconnects upon the increasingly reduction in the interconnect width, related issues on Cu interconnects, such as electron scattering at surfaces and grain boundaries, electromigration failure and surface oxidation, still need to be further understood and addressed. Besides this, the performance of low-k dielectrics and reliable barrier structures, which are also much important among the device parts, are required to be further improved to minimize the signal delay and to prevent penetration of different materials, respectively. On the basis of the paper published at Recent Patent on Nanotechnology 2007; 1: 193-209, this review will focus on recent patents and some studies on Cu metallization including Cu interconnect wires, low-k dielectrics and related barrier materials as well as manufacturing techniques in VLSI, which are one of the most essential concerns in microelectronic industry and decide further development of VLSI. This review will benefit for the design of the Cu metallization in the current VLSI.

Preliminary UWB channel study for wireless body area networks in medical applications

Ultra wideband (UWB) communications is a promising technology for wireless body area networks (WBAN) due to its very low power emission and robustness against multipath fading characteristics. The use of WBANs in the areas of healthcare and telemedicine is being seriously considered as a way of increasing the quality of medical services and of keeping under control the associated costs. Because the human body has a complex shape and consists of different tissues it is expected that the propagation of electromagnetic signals will have different characteristics than the ones found in other environments, e.g., offices, streets, etc. The contribution of the work described in this paper is to expand the knowledge of the UWB channel, for WBAN applications, in the frequency range of 3-11 GHz under scenarios expected to be found in the medical care field. The experimental measurements are used to develop UWB channel models which can then be applied to the design of efficient communications protocols.

Electromagnetic Signal Propagation in a Lorentz Dispersive Medium

Electromagnetic Signal Propagation in a Lorentz Dispersive Medium

Insight into the marine controlled-source electromagnetic signal propagation

In marine controlled-source electromagnetic (CSEM) surveys the subsurface is explored by emitting low-frequency signals from an electric dipole source close to the sea-bed. The main goal is often to detect and describe possible thin resistive layers beneath the sea-bed. To gain insight into how CSEM signals propagate, it is informative to study a stratified model. The electromagnetic field is then given in terms of integrals over TE- and TM-polarized plane-wave constituents. An asymptotic evaluation of the field integrals for large propagation distances results in explicit spatial expressions for the field components and the derived expressions can be used to analyse how the CSEM signals propagate. There are two major signal pathways in a standard CSEM model. One of these pathways is via the thin resistive layer and the resulting response is accounted for by a pole in the reflection response for the TM mode. The signal is propagating nearly vertically down to the resistor from the source, then guided while attenuated along the reservoir, before propagating nearly vertically up to the receiver. The response is slightly altered by the sea-bed interface and further modified in shallow water due to multiple reflections between the sea-surface and sea-bed at both the source and receiver sides. The other major signal pathway is via the resistive air half-space, the so-called airwave. The airwave is generated by the TE mode and interacts with the subsurface via vertically propagating signals reflected between the sea-surface and subsurface at both the source and receiver sides.

Investigation of the peculiarities of artificial electromagnetic signal propagation at high latitudes in the range 0.1–10 Hz

The results of measurements of the artificial electromagnetic signal in the range 0.1–10 Hz on the Spitsbergen archipelago are presented in this paper. The signal was emitted by a horizontal antenna located on the Kola Peninsula. Resonance spectra structures (RSSs) caused by the influence of the ionospheric Alfven resonator (IAR) were found in the artificial signal. The calculations of the field performed using the method of a two-dimensional telegraph equation for an anisotropic inhomogeneous model of the ionosphere allowed us to explain the main properties of the observed artificial RSS signal. Special attention was focused on the choice of the ionospheric model and calculation of the reflection coefficient for a plane wave normally incident on the ionosphere. The needed profiles of the ionospheric parameters were selected on the basis of the Upper Atmosphere Model (UAM) and IRI2007 model, while the atmospheric parameters were specified on the basis of MSIS-E-90. The advantages of the UAM model compared with the IRI for the description of the experimental results in a high-latitude region are shown in the paper.

Unified BER and optimum threshold analysis of binary modulations in simple and cascaded Rayleigh fading channels with switched combining

Following a unified analytical framework, the bit error rate (BER) of several coherent and non-coherent binary modulation schemes is derived for a switched diversity system. The two variants of switched combining that have been investigated are switch and stay combining and switch and examine combining. For channel modelling, at first a simple slow flat fading channel is assumed, where the amplitude attenuation obeys the Rayleigh distribution. Later the BER calculations are repeated for cascaded Rayleigh fading channel case. Rayleigh fading is the most popular model for electromagnetic signal propagation in wireless media when both or either of the transmitter/receiver is fixed. On the other hand, when both the transmitter and the receiver are mobile, a cascaded (or double) Rayleigh fading model is better suited. The applicability of these two models, namely simple and cascaded Rayleigh model, has been indicated by several theoretical studies and their suitability is established by various field measurements. In our paper, simple closed-form BER expressions as a function of switching threshold have been found and optimum switching thresholds have been computed for both these models as well as for both types of diversity combining described earlier. The results presented in this paper can be very useful for communication system designers to analyze link quality of switched diversity assisted systems in various wireless environments. Copyright © 2010 John Wiley & Sons, Ltd.

Studies of Scattering, Reflectivity, and Transmitivity in WBAN Channel: Feasibility of Using UWB

The Wireless Personal Area Network (WPAN) is one of the fledging paradigms that the next generation of wireless systems is sprouting towards. Among them, a more specific category is the Wireless Body Area Network (WBAN) used for health monitoring. On the other hand, Ultra-Wideband (UWB) comes with a number of desirable features at the physical layer for wireless communications. One big challenge in adoption of UWB in WBAN is the fact that signals get attenuated exponentially. Due to the intrinsic structural complexity in human body, electromagnetic waves show a profound variation during propagation through it. The reflection and transmission coefficients of human body are highly dependent upon the dielectric constants as well as upon the frequency. The difference in structural materials such as fat, muscles and blood essentially makes electromagnetic wave attenuation to be different along the way. Thus, a complete characterization of body channel is a challenging task. The connection between attenuation and frequency of the signal makes the investigation of UWB in WBAN an interesting proposition. In this paper, we study analytically the impact of body channels on electromagnetic signal propagation with reference to UWB. In the process, scattering, reflectivity and transmitivity have been addressed with analysis of approximate layer-wise modeling, and with numerical depictions. Pulses with Gaussian profile have been employed in our analysis. It shows that, under reasonable practical approximations, the human body channel can be modeled in layers so as to have the effects of total reflections or total transmissions in certain frequency bands. This could help decide such design issues as antenna characteristics of implant devices for WBAN employing UWB.

Manipulating microwaves with magnetic-dipolar-mode vortices

There has been a surge of interest in the subwavelength confinement of electromagnetic fields. It is well known that, in optics, subwavelength confinement can be obtained from surface plasmon (quasielectrostatic) oscillations. In this article, we propose to realize subwavelength confinement in microwaves by using dipolar-mode (quasimagnetostatic) magnon oscillations in ferrite particles. Our studies of interactions between microwave electromagnetic fields and small ferrite particles with magnetic-dipolar-mode (MDM) oscillations show strong localization of electromagnetic energy. MDM oscillations in a ferrite disk are at the origin of topological singularities resulting in Poynting vector vortices and symmetry breakings of the microwave near fields. We show that new subwavelength microwave structures can be realized based on a system of interacting MDM ferrite disks. Wave propagation of electromagnetic signals in such structures is characterized by topological phase variations. Interactions of microwave fields with an MDM ferrite disk and MDM-disk arrays open a perspective for creating engineered electromagnetic fields with unique symmetry properties.

Estimation of the penetration angle of a man-made tunnel using time of arrival measured by short-pulse cross-borehole radar

The relatively fast propagation of electromagnetic signals through empty man-made tunnels has played a key role in detecting deep underground tunnels using a short-pulse cross-borehole radar system. Our cross-borehole radar system measured the pulse signatures of an obliquely penetrating tunnel using eight different borehole pairs at a test site in Korea. Compared to the arrival times of the first peaks, the arrival times of the first received signals at an appropriate amplitude level provided an increasingly clear indication of the empty tunnel as its penetration angle became more oblique. A quadratic relationship between the arrival time of the first received signal and the oblique angle of the empty tunnel was obtained in pure granite.

Mathematical modeling of electromagnetic wave propagation in nonlinear electrodynamics

The eikonal method for an electromagnetic wave propagating according to the laws of non-linear electrodynamics in vacuum in external electromagnetic and gravitational fields is developed. A mathematical model of the propagation of electromagnetic signals in the parameterized post-Maxwellian electrodynamics in vacuum is constructed. As an example of using the proposed method, the angles of the nonlinear electrodynamical and gravitational curvature of the normal wave rays propagating in the field of a charged collapsar are calculated.

Evaluation of EGNOS Tropospheric Delay Model in South-Eastern Europe

The troposphere affects electromagnetic signal propagation causing signal path bending and the alteration of the electromagnetic wave velocity. Tropospheric delay can introduce a considerable error in satellite positioning if it is not properly estimated. The GPS signal delay can vary from 2 to 20 m depending on the elevation angles between the receiver and the satellite. Two basic types of delay prediction models exist. The first use surface meteorological parameters to estimate the value of the tropospheric delay, and the other models that do not require real-time meteorological input use average and seasonal variation data related to the receiver's latitude and day-of-year. This paper compares the performance of both types of model over a period of one year, comprising all seasons, to verify their accuracy over a longer period. The Saastamoinen model, known as one of the best performing prediction models, was taken as a reference and the global EGNOS model was used to check how the global estimates of the yearly averages of the meteorological parameters and their related seasonal variations comply with the real-time surface parameters.

Two-dimensional propagation of magnetocardiac T wave signals for characterizing myocardial ischemia

Instead of detecting electrical signals for diagnosing cardiac abnormalities, a promising alternative is to detect the magnetic signals generated from cardiac electrical currents. The system utilizing 64 low-transition-temperature superconducting quantum interference devices was tested to detect the time-dependent magnetocardiac signals that are spatially distributed over the heart. To achieve efficient acquisition and analysis, we propose a method to detect two-dimensionally, the T wave propagation of electromagnetic signals of beating hearts. In addition to characterizing the propagating behaviors, the differences between normal hearts and those with coronary artery disease were investigated.