Electromagnetic Field In Air Research Articles

Characterization and Production of PCB Structures With Increased Ratio of Electromagnetic Field in Air

Producing passive printed circuit board (PCB) structures in the millimeter-wave range includes some fundamental challenges, such as low manufacturing costs and high fabrication accuracy. These aspects, in general, have to be combined with low signal attenuation, precise simulation models, and a reliable producibility. This article shows a new method to manufacture different kinds of passive RF waveguides with reduced attenuation and decreased electrical length on low-cost PCB substrates. First, the complex material parameters of the used substrate and the used copper foil are extracted from 10 to 100 GHz to have accurate simulation models in CST Microwave Studio. This is necessary because the parameters provided by the manufacturer are often no longer generally valid in this frequency range. In addition, PCB materials have a significantly higher surface roughness compared with conventional materials for millimeter-wave applications. Therefore, the correct determination and the correct modeling of surface roughness is particularly important. Next, laminate is removed partially on the outer layer of the PCB to increase the electromagnetic field ratio in air. The undesired substrate is removed by a CO2 laser drilling machine by setting narrow drills sequentially. The RF performance of these waveguides is compared with those manufactured in conventional PCB technology according to attenuation and producibility.

Electromagnetic fields in air produced by underwater magnetic dipoles with attitude variation in real marine environment

ABSTRACTWireless data transmission from seawater to air is a challenging and valuable research hotspot. Ideally and theoretically, underwater electromagnetic (EM) waves can propagate across sea-air interface and the trans-media component in air can reach a great distance. However, in real marine environment, underwater antenna's attitude varies due to water current. In this paper, EM fields in air produced by underwater magnetic dipoles with varying attitude are investigated. The field distributions and intensity variations in air are presented. Experiments on sea were conducted and the data are compared with theoretical simulations. The results show that field in air is greatly affected by underwater antenna's attitude, and the effect is more obvious in vertical magnetic dipole than in horizontal one. In conclusion, it is indicated that EM waves have a great potential in wireless data transmission from seawater to air even if underwater antenna would have some attitude variation.

Theoretical analysis and experimental measurements of electromagnetic radiation from a horizontal electric dipole in shallow sea

ABSTRACTThe technologies of undersea detection and communication, undersea sensor networks, and geophysical exploration by means of electromagnetic (EM) waves have been of long-standing interest in marine science and engineering. Most of the previous researches, however, dealt with these problems in deep sea environment with half-space model. In this paper, EM radiation from a horizontal electric dipole (HED) submerged in shallow sea is studied. A set of formulas for EM fields in air and seawater are derived with a three-layer model. The field expressions consist of Sommerfeld integrals, which are computed using a complementary numerical integration technique. A proof of concept measurement system was designed and a trial was conducted on a shallow sea. Comparisons are made at different frequencies between the measured results and theoretical predictions, good agreements of them verify the effectiveness of the theoretical model.

Electromagnetic Fields Generated Above a Shallow Sea by a Submerged Horizontal Electric Dipole

Great attention has been paid to the propagation of electromagnetic (EM) waves across the sea surface due to its important applications. Most of the previous research, however, focus on the half-space model illustrating the deep sea environment. In this communication, by taking into account the presence of a seafloor, the EM fields generated above shallow sea by a submerged horizontal electric dipole have been investigated theoretically and experimentally with a three-layer model. A set of formulas for EM fields in air expressed by Sommerfeld integrals are derived with recursive propagation approach, and the fields are computed using a complementary numerical integration technique. The effects of frequency, sea depth, seafloor conductivity, and receiver height on the fields are discussed. An experiment was conducted on shallow sea, and the test results agree well with theoretical predication in the quasi-near range. A transmission distance over 3 km above the sea surface was realized with reasonable transmitting power, which shows the potential of our theoretical model for applications in shallow sea environment.

Estimation of electromagnetic field in air by a magnetic dipole in the sea based on a current sheet model

Considerable efforts have been made to investigate the electromagnetic (EM) field in air produced by a magnetic dipole in sea. The conventional methods for this investigation mostly involve complicated analysis of Sommerfeld-type integrals. To conveniently provide a meaningful physical explanation of the EM field radiation in a two-layered media, this study considers a current sheet at the sea-to-air interface created by an underwater magnetic dipole. This current behaves like an antenna located on the surface and creates a wave that propagates through the atmosphere. Analysis of this current sheet can take advantage of the Huygens–Fresnel principle. The results using this approach can be verified by previous calculation and experiments on the sea, and show good agreement with experimental data. The present approach, which involves simple algebra, can easily explain the physical aspect of the EM wave propagation across the sea-to-air interface.

Performance of Dipole Antenna in Underwater Wireless Sensor Communication

The technology about undersea sensing and networking using electromagnetic wave has become one of the key topics in marine science and engineering. In such applications, the proper antenna types will significantly affect the performance of electromagnetic wave transmission in seawater or across the seawater-to-air interface. Therefore, in this paper, the model of dipole antennas in a three layered conducting media (air-seawater-sea bottom) is built. The electromagnetic fields in air produced by different kinds of undersea dipole antennas are derived. The field expressions in air with the form of Sommerfeld integral are rapidly and efficiently evaluated by the fast Fourier transform method. The results show that the performance of horizontal electric dipole is superior to that of vertical electric dipole, and the performance of magnetic dipole is superior to that of electric dipole. The approach and conclusions in this paper can provide a theoretical basis and technical foundations for the selection of antenna type when the electromagnetic wave is used for data transmission between seawater and air.

Electromagnetic field radiated in air from a horizontal/vertical magnetic dipole in sea

The propagation characteristics of electromagnetic (EM) waves across the seawater–air interface influence seawater to air communication. The type of underwater antenna determines EM wave propagation performance. However, studies rarely compared the performance of horizontal and vertical magnetic dipoles (HMD and VMD). In this study, the EM fields in air due to HMD/VMD immersed in sea were derived to provide a basis for selecting a suitable underwater antenna for EM wave propagation in undersea–air communication. Analytic results were obtained from the model of a three-layered conducting media. Associated expressions in air were numerically calculated using the fast Fourier Transform algorithm to present the propagation curves and the distribution patterns of the EM fields. A proof of concept measurement system was constructed, and sea experiments were conducted and compared with theoretical studies. The maximum transmitting–receiving distance in the experiment was achieved by the HMD. The theoretical and experimental results indicate that the HMD antenna is superior to the VMD antenna and that the suggested band of EM wave is feasible for transmission across the seawater–air interface.

Electromagnetic Field in Air Produced by a Horizontal Magnetic Dipole Immersed in Sea: Theoretical Analysis and Experimental Results

In recent years, data transmission from seawater into air across the sea surface has attracted considerable interest and is essential for undersea sensing and networking applications. In particular, electromagnetic (EM) wave propagation across the sea surface via a seawater-air path has great potential for long-distance transmission, thus providing a possible solution for sensing and networking problems. However, current related theoretical analyses and experimental results are not sufficient to support research and development in the domain. Therefore, based on previous studies, this study theoretically and experimentally investigates EM wave propagation from a horizontal magnetic dipole (HMD), namely, a loop antenna immersed in seawater radiating into the air. A set of mathematical expressions is formulated for a model of three-layered conducting media on the basis of Maxwell's equations. In addition, a proof of concept measurement system was designed and built. A trial was conducted on the sea, and the results were in good agreement with the theoretical analysis. A horizontal transmission distance up to 574 m over the sea surface was achieved using a small loop antenna operated at 19 kHz and with an input power of less than 10 W. Therefore, the approach has been proven to be promising.

Influence of frequency‐dependent soil electrical parameters on the evaluation of lightning electromagnetic fields in air and underground

This paper is aimed at analyzing the influence of the frequency‐dependent behavior of the ground electrical parameters (conductivity and ground permittivity) on the electromagnetic field radiated by a cloud‐to‐ground lightning return stroke. Both radiation in air (over the conducting ground plane) and underground are considered in the analysis. The adopted method is based on the classical Sommerfeld's theory and takes advantage of an efficient ad hoc numerical procedure to face with the slow converging Sommerfeld's integrals. This feature allows the electromagnetic field to be computed without any sort of mathematical approximation and, since it is carried out in the frequency domain, can be used either if the ground permittivity and conductivity are considered constant or if they vary with the working frequency with any functional law. Simulations have been performed to identify the cases in which the approximation of constant ground permittivity and conductivity leads to satisfactory results. It is shown that for soils with water contents of 2% to 10% (ground conductivities in the order of 0.001 to 0.01 S/m), the assumption of constant electrical parameters appears to be reasonable. However, for either very poorly conducting soils (10−4 S/m or so) or highly conducting soils (10−1 S/m), the electromagnetic field components appear to be significantly affected by the frequency dependence of the ground electrical parameters.

ELECTROMAGNETIC FIELD FROM A HORIZONTAL ELECTRIC DIPOLE ON THE SURFACE OF A HIGH LOSSY DIELECTRIC COATED WITH A UNIAXIAL LAYER

In this paper, the explicit formulas are derived for the six components of the electromagnetic field in air excited by a horizontal electric dipole over a planar high lossy dielectric coated with an anisotropic uniaxial layer. Similar to the case of the three-layered region consisting of air, a uniaxial layer, and a perfect conductor, the total field consists of the direct field, the ideal reflected field or the field of an ideal image, the lateral-wave field, and the trappedsurface-wave field. It should be pointed out that the trapped surface wave can be separated into the trapped wave of electric type and magnetic type. The wave numbers in the ρ direction of electric-type trapped surface wave, which are between k0 and kL, are different from those of the magnetic-type trapped surface wave, which are between k0 and kT . When the thickness l of the uniaxial layer satisfies nπ < kT kL (k 2 L − k2 0) · l < (n + 1)π, there are n + 1 modes of the electric-type trapped surface waves. When the thickness l satisfies (n− 12)π < (k2 T − k2 0) · l < (n+ 12)π, there are n modes of magnetictype trapped waves.

Electromagnetic field generated by a horizontal electric dipole near the surface of a planar perfect conductor coated with a uniaxial layer

In this paper, simple explicit formulas are derived for six components of the electromagnetic field in air from a horizontal electric dipole over a planar perfect conductor coated with a uniaxially anisotropic layer. The total field consists of the direct field, the ideal reflected field or field of an ideal image, the lateral-wave field, and the trapped-surface-wave field. The computations and discussions show that the trapped surface waves including the electric-type and magnetic-type trapped surface waves cannot be neglected when the dipole and the observer are on or close to the surface of the uniaxially anisotropic layer. Both trapped surface waves of electric type and magnetic type attenuate exponentially in the z/spl circ/ direction. The wave numbers in the /spl rho//spl circ/ direction of electric-type trapped surface wave, which are between k/sub 0/ and k/sub L/, are different from those of the magnetic-type trapped surface wave, which are between k/sub 0/ and k/sub T/. The electric-type trapped surface wave can be excited efficiently when the thickness l of the uniaxially anisotropic layer satisfies the condition 0<(k/sub T//k/sub L/) (k/sub L//sup 2/-k/sub 0//sup 2/)/sup 1/2//spl middot/l</spl pi/ and the magnetic-type trapped surface wave can be excited when the thickness l of the dielectric layer satisfies the condition (/spl pi//2)<(k/sub T//sup 2/-k/sub 0//sup 2/)/sup 1/2//spl middot/l</spl pi/. When the thickness l of the uniaxially anisotropic layer satisfies n/spl pi/<(k/sub T//k/sub L/) (k/sub L//sup 2/-k/sub 0//sup 2/)/sup 1/2//spl middot/l<(n+1)/spl pi/, there are n+1 modes of the electric-type trapped surface waves to propagate along the uniaxial surface, and when the thickness l of the uniaxially anisotropic layer satisfies (n-(1/2))/spl pi/<(k/sub T//sup 2/-k/sub 0//sup 2/)/sup 1/2//spl middot/l<(n+(1/2))/spl pi/, there are n modes of magnetic-type trapped waves to propagate along the uniaxial surface. When the conditions k/sub 0//spl rho//spl Gt/1 and z+d/spl Lt//spl rho/ are satisfied, both the electric-type and magnetic-type lateral waves with the wave numbers being k/sub 0/ are excited.

ELECTROMAGNETCI FIELD FROM A HORIZONTAL ELECTRIC DIPOLE IN THE SPHERICAL ELECTRICALLY EARTH COATED WITH N-LAYERED DIELECTRICS

In this paper, the electromagnetic field in air from a radiating horizontal electric dipole located in the homogeneous isotropic spherical electrically earth coated with N -layered dielectrics is investigated anew. The starting point is based on the formulas for the electromagnetic fields in air from vertical electric and magnetic dipoles situated in air above the surface of the earth coated with N layered dielectrics. The complete explicit formulas are derived for the electromagnetic fields in the earth due to vertical electric and magnetic dipoles located in air. By using reciprocity theorem, the formulas are readily obtained for the six components of the electromagnetic field in air radiated by a horizontal electric dipole located in the earth.

Radiation of horizontal electric dipole on large dielectric sphere

The electromagnetic field in air of a radiating electric dipole located below and tangential to the surface of a homogeneous, isotropic and optically dense sphere is studied anew. The starting point is the eigenfunction expansion for the field in spherical harmonics, which is now converted into series of integrals via the Poisson summation formula. A creeping-wave structure for all six components along the boundary is revealed that consists of waves exponentially decreasing through air and rays bouncing and circulating inside the sphere. The character of individual modes of propagation and the interplay between “electric” and “magnetic” types of polarization are investigated. Connections with and differences from standard ray optics and the cases of the radiating vertical dipole and scalar plane-wave scattering are outlined.

Thin-skin electromagnetic fields in the neighbourhood of surface-breaking cracks in metals

Electromagnetic non-destructive evaluation techniques are widely used to detect and size surface-breaking cracks in metal structures and components. The precise distribution of the electromagnetic field around such a crack depends on the frequency of the applied field, the material properties of the metal and the crack geometry. In many situations, the skin depth of the electromagnetic field in the metal is small compared with the crack dimensions. If this is the case, the crucial parameter that determines the way the electromagnetic field in air couples to the field in the metal is m = μ 0 l / μδ , where μ and μ 0 are the metal and free space permeabilities respectively and l / δ is the ratio of the crack length scale l to the skin depth δ . If the metal is ferromagnetic, m can take a wide range of values and the distribution of the electromagnetic field around the crack is very different in the two limiting cases m = 0 and m ≫ 1. In the first case, the magnetic flux emerging from the crack is directed into the metal surface whereas in the second case, the flux is directed into free space. In this work, the distribution of the electromagnetic field around a surface-breaking crack is determined for arbitrary values of m . The theory is developed for cracks of general shape and numerical calculations of the free-space components of the magnetic field are made for rectangular and semi-elliptical shaped cracks. The numerical predictions are found to be in good agreement with experimental measurements of the magnetic field above a rectangular slot, cut in a flat plate of mild steel.

Experimental investigation on the behaviour of light propagating through electromagnetic fields in air

A series of experiments are described in an attempt to explain some recent observations by Sadeh. These observations suggest a possible decrease in the frequency of electromagnetic radiation that passes near the Sun or the Earth. The present experiments prove to a high accuracy that such a frequency shift cannot be caused by electrostatic fields or by magnetic fields.

Physical limitations on the measurement of transient fields in air and in dissipative media using electric and magnetic probes

The properties of electric and magnetic probes for the measurement of transient electromagnetic fields in air and in dissipative media are discussed briefly. It is shown that the effective height of an electrically small loop is independent of the ambient medium. This is also virtually true for a thin electrically short dipole (or monopole). If the open-circuit voltage of a magnetic probe can be measured accurately, it is possible (in principle) to reconstruct the time history of the incident magnetic field, even if the loop is immersed in dissipative media of unknown characteristics. The time function of the open-circuit voltage of an electric probe is essentially a replica of the time history of the incident electric field, even when the probe is immersed in a dissipative medium. For impedance-loaded probes the equivalent circuit of the receiving antennas involves the source impedances of the probes. These depend on the properties of the environment. In a dissipative medium a distortion of the response to transient fields results.