Magnetic Current Loop Research Articles

A Detailed Model of Magnetic Field Sources of the Earth’s Core Obtained by Solving the Inverse Problem of Magnetometry

Abstract —Magnetic field sources are sometimes approximated by magnetic dipoles or current loops. The usefulness of such approximations is not obvious at the initial stage of the study of objects. Investigating them in detail requires volumetric magnetic field sources. In this paper, they are represented by magnetized prisms. Such a model is valid due to the equivalence of current and magnetized objects. As there should be no real magnetization in the core, this property of a virtual prism to generate a magnetic field strength is referred to as virtual or effective magnetization (EM), which is determined for each prism by solving the inverse problem via the adaptive method. Initial data for solving the inverse problem are the Z vector components of the main magnetic field of the IGRF-2005 model in the geocentric coordinate system. Based on the effective magnetization and known formulas, the bulk current distribution, the bulk current density, and the magnetic moments of prisms of a two-layer core model are obtained. Their sum coincides with the magnetic moment of the virtual central dipole of the core, but, as many scientists assumed, the central dipole is not actually distinguished. At the same time, four significant inhomogeneities are identified in the core, which create the Canadian, Siberian-Asian, Australian, and negative South Atlantic global anomalies on the Earth’s surface. Based on the analysis of the results obtained, assumptions are made that the current generating the magnetic field is the motion of a positively weakly charged liquid of the core. Liquid motion is created by the rotation of the Earth and the decelerating gravitational forces of the Moon and the Sun. Arguments are given to support these assumptions. The results are illustrated in figures.

Triple-Band Reconfigurable Low-Profile Monopolar Antenna With Independent Tunability

This article proposes a reconfigurable low-profile monopolar antenna with triple-band independent tuning capability. The antenna is based on the concept of a center-fed patch with shortings to achieve omnidirectional radiation patterns. Instead of using vias, varactor-loaded stubs are utilized to create reconfigurable equivalent shorting points. The triple bands can be achieved by using three sets of stubs. This configuration results in three magnetic current loops that spatially overlap at different independently tunable frequencies. Measurement results show that the design obtains three independent tunable frequencies centered at 2.51, 3.56, and 4.62 GHz with -10 dB relative tuning ranges of 22.8%, 22.8%, and 16.7%, respectively. The antenna radiates omnidirectionally with vertical polarization in the three sweeping bands. The proposed concept can be extended to a larger number of bands by adding sets of stubs with considerations of coupling and impedance matching.

Force exerted by a magnet on a circular coil

Interaction forces between magnetic fields and current loops play a central role in the theory of magnetism. This work describes a reasonably simple and cheap experiment for demonstrating this issue: the force on a thin coil due to a nearby cylindrical magnet. The magnitude of the force as well as its attractive/repulsive character is comfortably revealed by means of a balance. A first test clearly reveals the linearity between force and current. With some additional care, it is also possible to investigate the force–distance relationship and to compare it to simple models.

Dual Band Metamaterial Antenna For LTE/Bluetooth/WiMAX System

A compact metamaterial inspired antenna operate at LTE, Bluetooth and WiMAX frequency band is introduced in this paper. For the lower band, the design utilizes an outer square metallic strip forcing the patch to radiate as an equivalent magnetic-current loop. For the upper band, another magnetic current loop is created by adding metamaterial structure near the feed line on the patch. The metamaterial inspired antenna dimension of 42 × 32 mm2 compatible to wireless devices. Finite integration technique based CST Microwave Studio simulator has been used to design and numerical investigation as well as lumped circuit model of the metamaterial antenna is explained with proper mathematical derivation. The achieved measured dual band operation of the conventional antenna are sequentially, 0.561~0.578 GHz, 2.346~2.906 GHz, and 2.91~3.49 GHz, whereas the metamaterial inspired antenna shows dual-band operation from 0.60~0.64 GHz, 2.67~3.40 GHz and 3.61~3.67 GHz, respectively. Therefore, the metamaterial antenna is applicable for LTE and WiMAX applications. Besides, the measured metamaterial antenna gains of 0.15~3.81 dBi and 3.47~3.75 dBi, respectively for the frequency band of 2.67~3.40 GHz and 3.61~3.67 GHz.

An Electromechanically Modulated Permanent Magnet Antenna for Wireless Communication in Harsh Electromagnetic Environments

High-frequency electromagnetic waves are greatly scattered and attenuated by soil, rocks, water, and the human body, which impede their propagation across these media. However, low-frequency magnetic waves propagate with low attenuations through these dispersive media as long as these media are nonmagnetic. Unlike static electric fields that can be produced by “free” positive/negative charges, static magnetic fields are divergence-free and thus can be produced only by particles with noninteger spins (i.e., electrons), or permanent magnets, or current loops. Fields produced by these dipoles decay steeply as a third-order function of distance. Hence, magnetic current loops require excessively large currents to produce detectable magnetic field at large distances. However, rare-earth magnets with surface magnetic flux densities of 0.3–0.6 T, provide sufficiently large fields at large distances, thus the fields produced by these magnets that can be modulated by mechanically modulating the magnets for portable wireless magnetic field communication. Here, we present the development of an electromechanically modulated permanent magnet antenna operating at a frequency of 22 Hz, producing a magnetic flux density of $0.6~\mu \text{T}$ amplitude at 1 m. This antenna requires a starting energy of 0.48 J and it is capable of data rate of 8 b/s. This magnet antenna can reliably transmit binary data over a distance of up to 70 cm through obstacles that would severely hamper electromagnetic wave propagation.

A Frequency-Reconfigurable Dual-Band Low-Profile Monopolar Antenna

A concept of a low-profile monopolar antenna operating in two independently reconfigurable frequency bands is introduced in this paper. For the lower band, the design utilizes a center-fed patch with shorting rods at its edges, forcing the patch to radiate as an equivalent magnetic-current loop. For the upper band, another magnetic current loop is created by adding four symmetrical resonant slots on the patch, which radiates almost independently of the shorted patch. To allow coverage of a larger bandwidth, two sets of varactor diodes are used to independently control the resonance frequencies of the two bands. As a validation of the proposed concept, two antenna prototypes, with and without reconfigurabilities, have been optimized and fabricated. Measurement results show that the low-profile reconfigurable monopolar antenna achieves two independent tunable bands, with −10-dB-tuning ranges of 31% and 22% centered at about 0.9 and 1.7 GHz, respectively. The antenna height is only $0.020\lambda _{\text {min}}$ , where $\lambda _{\text {min}}$ is the free-space wavelength at the minimum operating frequency. Importantly, stable omnidirectional patterns and vertical polarization are consistently achieved across both tuning ranges.

Planar Triorthogonal Diversity Slot Antenna

This communication proposes an easily manufacturable multifunction multiport planar slot antenna with triorthogonal pattern diversity. Distinct radiation patterns are emitted via a common square radiative slot by exploiting three orthogonal modes. These slot modes consist of a magnetic current loop mode with an omnidirectional linearly polarized (OLP) radiation pattern, and two degenerated linear slot modes radiating broadside with orthogonal linear polarizations (LPs). The triorthogonal patterns are obtained in an overlapping frequency band, and the mutual coupling between the ports is minimized through a differential feeding arrangement. This new concept of multiport diversity slot antenna is validated experimentally at a frequency of 5.9 GHz, successfully demonstrating the operation modalities of OLP and LP radiation patterns. A minimum triorthogonal overlapping impedance bandwidth of 2.3% is measured with interport coupling below −35 dB. The proposed antenna could be used as a pattern and polarization diversity antenna, where additionally, a linear combination of the primary triorthogonal patterns can be exploited to further enhance flexibility in pattern generation.

Wideband substrate‐integrated monopole antenna

ABSTRACTA coaxial probe fed wideband low‐profile electric monopole cavity antenna with measured impedance bandwidth of 56% at a central operating frequency of 8 GHz is proposed. The antenna, based on a modified shorted square patch, effectively forms a substrate‐integrated cavity with four curved radiating slots at its periphery. The concave curvature of these four radiating slots provides a magnetic current loop mode while increasing bandwidth and reducing volume of the resonator. The proposed design may be easily fed using a 50 Ω probe feed and capacitive gap, and is robust to manufacturing tolerances, as parasitic modes are not excited. The design is compatible with applications requiring a vertically polarized signal with respect to the antenna surface. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1855–1857, 2016

340-GHz SIW Cavity-Backed Magnetic Rectangular Slot Loop Antennas and Arrays in Silicon Technology

A 340-GHz on-chip antenna (OCA) with high-gain and high-radiation efficiency is designed using a standard ${0}.{13}\hbox{-}\upmu {\rm m}$ SiGe BiCMOS technology without any postprocesses. In the proposed OCA structure, a rectangular slot loop is etched in the upper wall of a substrate integrated waveguide (SIW) to form a magnetic current loop radiator. The SIW structure forms a back cavity to suppress the surface waves and separate the radiation aperture from the low-resistivity substrate. Furthermore, the side wall of the SIW cavity and the edge of the slot form a ${{{\lambda }}_{{g}}}/4$ resonator to reflect the power back to the slot loop. As a result, the radiation efficiency is improved. By etching a slot properly in the SIW upper wall, another resonating point is constructed and hence, the bandwidth is broadened. Single antenna element and a ${2} \times {2}$ array are both designed and fabricated with- and without- the slot structure; a maximum gain of 7.9 dBi with the radiation efficiency of 48% at 340 GHz is achieved for the proposed SIW cavity-backed antenna structure.

Numerical Modeling for Excitation and Coupling Transmission of Near Field Around the Metal Drilling Pipe in Lossy Formation

The wireless transmission of the logging signal by using metal drill pipe as a dipole antenna with an extremely asymmetric feeding is one of the potential techniques for logging (or measurement) while drilling (LWD, or MWD) and has drawn a lot of attention in recent decades. In this paper, a precise numerical model based on numerical mode matching (NMM) theory has been built for solving the very low-frequency radiation of the asymmetrical feeding dipole antenna in the layered background medium. First of all, the feeding gap of the antenna has been equalized as a magnetic current loop, and NMM numerical solutions have been applied to expand the field excited by the equivalent source, and then, the characteristics of input impedance and the near field radiated by the dipole have been calculated based on the field solutions. Furthermore, the results have been compared with the corresponding results of the “method of moments” and the “equivalent transmission line model,” respectively. The inference of the relevant parameters, such as the asymmetry of the feeding, the working frequency, the conductivity of the formation, the size of the insulating gap, the size of the casing, etc., on the transmission performance of the signal of electromagnetic MWD (EM-MWD) system has been discussed. In addition, the method for receiving the LWD signal transmitted to the ground is also evaluated, and an adaptive impedance matching scheme in transmitting terminal is proposed based on the numerical analysis in this paper.

Application of a Cavity Resonator Model for Characterization and Estimation of Radiation From a PCB–Chassis System

The electric far-field radiated from a printed circuit board (PCB)-chassis system is characterized using a cavity resonator model employing the far field calculated using an equivalent magnetic current loop. The inductive network method with measured current flowing through screws as a stimulus is used to calculate the frequency spectra of the electric field strength along the edge of the PCB with various locations of screws that connect the PCB ground to the chassis. Electric far fields from the equivalent magnetic current loop were derived using correction coefficients that incorporate the asymmetric dimensions of a parallel pair of PCB planes and the chassis. The calculation results reveal that the horizontal far field exceeds the vertical far field due to the asymmetric size coefficients and exhibit good agreement with the measurement results.

Magnetic current loop as a source model for finite thin‐wire antennas

AbstractThe paper deals with the concept of magnetic current loop as a source model for finite thin‐wire antennas. The formulation is based on the Pocklington integro‐differential equation with reduced kernel, which is handled by means of various numerical techniques, mostly using the Galerkin–Bubnov variant of Indirect Boundary Element Method. Extensive numerical experiments were carried out on various dipole and monopole antennas using different sources (delta gap, magnetic frill, and magnetic current loop), and results for input admittance are compared with measured data. The magnetic current loop source ensures accurate solution for input admittance. Copyright © 2014 John Wiley & Sons, Ltd.

Magnetic-Current-Loop-Induced Electric Dipole Antenna Based on Substrate Integrated Waveguide Cavity

In this letter, a novel dipole antenna based on substrate integrated waveguides (SIWs) is presented. The dipole antenna radiates through the equivalent magnetic current loops on the top and bottom annular ring slot that is excited by the fundamental mode of the SIW cavity. Therefore, the proposed dipole possesses a vertical polarization perpendicular to the metallic plane. Moreover, thanks to normal electric field, the proposed dipole is less affected by the ground plane size and surrounding metal. The proposed antenna topology provides a very easy way to realize vertical dipole antenna by just using planar circuits and is promising to be used as a fundamental element to realize antenna arrays.

Principle of Emagnetodynamics For Composite Magnetic Pole

It is shown in this paper that geometry provides the key to the emagnetodynamics principle of operation of the machine (invented by Dr. Ezekiel Izuogu) which has an unexpected feature of driving a motor with static magnetic field. Essentially, because an array of like magnetic poles of the machine is arranged in a half circular array of a cylindrical geometry, the array creates a non-pointlike magnet pole that may be represented by a “magnetic current loop” at the position of the pivot of the movable arm. As a result, in three-dimensional space, it is possible to characterize the symmetry of the stator magnetic field B and the magnetic current loop J as a geno-dual (cube-hexagon) system by a 6-vector (J,B) (with J.B =6 0) comprising a 4x4 antisymmetric tensor analogous to the conventional electric and magnetic 6-vector (E,B) (with E.B =6 0) comprising the 4x4 antisymmetric tensor of classical electrodynamics. The implications are discussed.

Wireless propagation in circular tunnels

We study models for propagation in circular tunnels. The excitation is either a circular magnetic or circular electric current loop. We produce expressions for the fields in terms of a Fourier transform over the axial variable. We then produce the modes in the lossy structure by contour integration techniques. We include numerical results for the field intensity both as a function of axial distance and as a function of radial distance for several frequencies, radii, and constitutive parameters of interest. We comment in particular concerning the specific form of the field both near to and far from the antenna source.

Abelian links, monopoles, and glueballs in SU(2) lattice gauge theory

We investigate the masses of 0 + and 2 + glueballs in SU(2) lattice gauge theory using abelian projection to the maximum abelian gauge. We calculate glueball masses using both abelian links and monopole operators. Both methods reproduce the known full SU(2) results quantitatively. Positivity problems present in the abelian projection are discussed. We study the dependence of the glueball masses on magnetic current loop size, and find that the 0 + state requires a much greater range of sizes than does the 2 + state.

A magnetic current loop array in a reflector antenna

A magnetic current loop antenna array is designed, implemented, and measured. Radiation pattern, input impedance, and efficiency of the array are presented. The array is intended as a feed in a reflector antenna. Using a 360 mm solid dish, the overall gain of the reflector antenna is 24.6 dB at 9 GHz. The tolerance in placing the feed at the focal point of the dish is high. The present feed is low cost, self-supportive, robust, and easy to manufacture. It is an ideal substitute for the horn in a TVRO or VSAT antenna.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Shielding of field produced by lightning type current pulse through metallic cylinders

The paper presents a method of estimation of field in a metallic conductor excited by lightning type current pulse for (i) when the return path is provided through a single conductor and (ii) when the return path is provided by the conductors forming the cage in which the excited conductor is enclosed. In the first case, analysis is carried out by replacing the current loop by an equivalent dipole, and solving the Helmholtz equation satisfied by the magnetic type Hertz vector. in the second example, when the excited conductor is enclosed in an axis symmetric cage, the entire circuit is replaced by an equivalent magnetic current loop, and the expressions for the field components are derived using the principle of duality. Analysis presented for this example is applicable to restricted case of axially symmetric cage. Numerical data on components of electric and magnetic fields are presented.

Magnetostatic image theory for the permeable sphere

The image of an electrostatic point charge in a conducting sphere, produced by Kelvin's inversion theory, has become well-known since its formulation in 1848. The corresponding image theory in terms of a point charge plus a line charge was recently developed for the dielectric sphere. This theory is adapted to the magnetically polarizable sphere with magnetic charges, dipoles, or current loops as sources. For the current loop, the image is seen to consist of a conical surface current plus an edge line current with expressions simple enough to allow numerical computations with a pocket calculator. A recently published result for the superconducting sphere is seen to be a special case of the present theory for mu =0. >

A ring cavity antenna of wide beamwidth

AbstractMobile telecommunication systems by satellite meet the requirement of antenna radiation pattern of wide beamwidth. The wide beamwidth of the circular microstrip disk antenna is obtained by high dielectric constant substrate. However, the dielectric losses and difficulty in manufacturing are problems for high dielectric constant materials.Wide beamwidth is obtained also using the antenna with an electrically small magnetic current loop.This paper presents the ring cavity antenna without dielectric materials. It also has electrically small magnetic current loop. Antenna characteristics calculated by the cavity model showed that the ring cavity antenna has wide beamwidth. Theoretical values are verified also by the measured radiation pattern and the input impedance.