ELECTROMAGNETIC FIELDS OF A SMALL LOOP ANTENNA ON THE SURFACE OF A POLARIZABLE MEDIUM

Geophysics ◽  
1964 ◽  
Vol 29 (5) ◽  
pp. 814-831 ◽  
Author(s):  
B. K. Bhattacharyya
Keyword(s):  
Electromagnetic Fields ◽  
Current Source ◽  
Approximate Expression ◽  
Characteristic Parameter ◽  
Step Function ◽  
Loop Antenna ◽  
Electrode Polarization ◽  
Polarizable Medium ◽  
Small Loop ◽  
Rate Of Decay

Studies are made in this paper on the characteristics of the electromagnetic fields produced by a small loop antenna placed on the surface of a medium which exhibits induced‐polarization effects. An approximate expression for the effective impedance of a polarizable medium is used for this purpose. Both the real and imaginary parts of the impedance are appreciably frequency‐dependent. Different expressions suitable for specific ranges of time and specific values of the characteristic parameter of the medium are obtained for the fields when the antenna is excited by a step‐function current source. The step‐function responses show marked differences in characteristics as the parameter of the medium is increased from very small values, typical of membrane polarization, to very large values corresponding to electrode polarization. The rate at which the magnitude of the transients decays with time is highly dependent on this parameter. The rate of decay in the initial small part of the transient curve increases, whereas in the remaining major part the rate decreases with rise in the value of the parameter.

ELECTROMAGNETIC FIELDS OF A VERTICAL MAGNETIC DIPOLE PLACED ABOVE THE EARTH’S SURFACE

Geophysics ◽  
1963 ◽  
Vol 28 (3) ◽  
pp. 408-425 ◽  
Author(s):  
B. K. Bhattacharyya
Keyword(s):  
Electromagnetic Fields ◽  
Current Source ◽  
Step Function ◽  
Impedance Function ◽  
Low Frequencies ◽  
Primary Loop ◽  
Mutual Impedance ◽  
The Earth ◽  
Receiving Antenna ◽  
Rate Of Decay

Electromagnetic fields due to a small loop antenna placed above the surface of a homogeneous and isotropic earth have been calculated. The effect of both the conduction and displacement currents are taken into account. Because of the complexity of the functions defining the fields, expressions valid separately for high and low frequencies are developed for the electric and magnetic field components. These expressions are then utilized to determine, for a step‐function current source, (a) the mutual impedance function [Formula: see text] between the primary loop and a small length of wire and (b) the voltage v(t) induced in a secondary loop. Two parameters are used to fix the locations of the primary loop and the receiving antenna with respect to the earth. A number of curves are plotted showing the mutual impedance function and the voltage function against time for different values of the parameters and the conductivity and the permittivity of the earth. With increase in either the conductivity or the permittivity, the amplitude and the rate of decay of the two functions decrease appreciably. However, the amplitudes of both [Formula: see text] and v(t) become smaller and the rate of decay higher as the receiving antenna is gradually lifted vertically from the ground. For all values of permittivity, the amplitude of the mutual impedance rises to a maximum with the horizontal separation between the two antennas before beginning to decrease, but at the same time the rate of decay of the transient becomes faster. With increase in the horizontal separation, the amplitude of the voltage function decreases inversely as the fifth power of the distance between the image of the transmitting dipole and the receiving antenna, but the rate of decay increases markedly.

scholarly journals KARAKTERISTIK MAGNETIC LOOP PROBE POLIGONAL SEBAGAI APLIKASI PENGUKURAN NEAR FIELD

2020 ◽  
Vol 11 (1) ◽  
pp. 217-222
Author(s):  
Haryo Dwi Prananto ◽  
Priyo Wibowo ◽  
Tyas Ari Wahyu Wijanarko ◽  
Wuwus Ardiatna ◽  
R. Harry Arjadi
Keyword(s):  
Near Field ◽  
Magnetic Loop ◽  
Vector Network Analyzer ◽  
Loop Antenna ◽  
Network Analyzer ◽  
Small Loop

Pada pengujian kompatibilitas elektromagnetik khususnya pada pengukuran near field, pengukuran medan magnet sangat diperlukan. Salah satu alat pengukuran yang digunakan adalah magnetic loop probe.  Penelitian ini dilakukan untuk membandingkan loop probe pada jumlah sisi geometrinya, dan belum ada referensi yang membahas tentang topik ini. Magnetic loop probe didesain dalam tujuh bentuk geometri yaitu bentuk segi 3 (ada dua model), segi 4, segi 6, segi 8, segi 10, dan segi tak hingga (lingkaran) dimana parameter keliling geometrinya sama. Magnetic loop probe didesain dengan menggunakan perhitungan sebagai small loop antenna Karateristik kelima desain probe dianalisis dengan mengukur S21 sebagai sensitivitas menggunakan Vector Network Analyzer. Karateristik bentuk probe maupun gain dan sensitivitasnya  dibahas dalam makalah ini.

Integral Equation Formulations and Related Numerical Solution Methods in Some Biomedical Applications of Electromagnetic Fields

2020 ◽  
pp. 249-267
Author(s):  
Dragan Poljak ◽  
Mario Cvetković ◽  
Vicko Dorić ◽  
Ivana Zulim ◽  
Zoran Đogaš ◽  
...  
Keyword(s):  
Integral Equation ◽  
Numerical Solution ◽  
Nerve Fiber ◽  
Electromagnetic Fields ◽  
Biomedical Applications ◽  
Current Source ◽  
Myelinated Nerve Fiber ◽  
Surface Integral ◽  
Myelinated Nerve ◽  
Solution Methods

The paper reviews certain integral equation approaches and related numerical methods used in studies of biomedical applications of electromagnetic fields pertaining to transcranial magnetic stimulation (TMS) and nerve fiber stimulation. TMS is analyzed by solving the set of coupled surface integral equations (SIEs), while the numerical solution of governing equations is carried out via Method of Moments (MoM) scheme. A myelinated nerve fiber, stimulated by a current source, is represented by a straight thin wire antenna. The model is based on the corresponding homogeneous Pocklington integro-differential equation solved by means of the Galerkin Bubnov Indirect Boundary Element Method (GB-IBEM). Some illustrative numerical results for the TMS induced fields and intracellular current distribution along the myelinated nerve fiber (active and passive), respectively, are presented in the paper.

Integral Equation Formulations and Related Numerical Solution Methods in Some Biomedical Applications of Electromagnetic Fields

2018 ◽  
Vol 9 (1) ◽  
pp. 65-84 ◽  
Author(s):  
Dragan Poljak ◽  
Mario Cvetković ◽  
Vicko Dorić ◽  
Ivana Zulim ◽  
Zoran Đogaš ◽  
...  
Keyword(s):  
Integral Equation ◽  
Numerical Solution ◽  
Nerve Fiber ◽  
Electromagnetic Fields ◽  
Biomedical Applications ◽  
Current Source ◽  
Wire Antenna ◽  
Myelinated Nerve Fiber ◽  
Myelinated Nerve ◽  
Numerical Solution Methods

The paper reviews certain integral equation approaches and related numerical methods used in studies of biomedical applications of electromagnetic fields pertaining to transcranial magnetic stimulation (TMS) and nerve fiber stimulation. TMS is analyzed by solving the set of coupled surface integral equations (SIEs), while the numerical solution of governing equations is carried out via Method of Moments (MoM) scheme. A myelinated nerve fiber, stimulated by a current source, is represented by a straight thin wire antenna. The model is based on the corresponding homogeneous Pocklington integro-differential equation solved by means of the Galerkin Bubnov Indirect Boundary Element Method (GB-IBEM). Some illustrative numerical results for the TMS induced fields and intracellular current distribution along the myelinated nerve fiber (active and passive), respectively, are presented in the paper.

Electromagnetic induction by a finite electric dipole source over a 2-D earth

Geophysics ◽  
1993 ◽  
Vol 58 (2) ◽  
pp. 198-214 ◽  
Author(s):  
Martyn J. Unsworth ◽  
Bryan J. Travis ◽  
Alan D. Chave
Keyword(s):  
Finite Element ◽  
Electromagnetic Fields ◽  
Electric Dipole ◽  
Numerical Solutions ◽  
Current Source ◽  
Three Dimensional ◽  
Iterative Solution ◽  
Electromagnetic Response ◽  
Dipole Source ◽  
Horizontal Electric Dipole

A numerical solution for the frequency domain electromagnetic response of a two‐dimensional (2-D) conductivity structure to excitation by a three‐dimensional (3-D) current source has been developed. The fields are Fourier transformed in the invariant conductivity direction and then expressed in a variational form. At each of a set of discrete spatial wavenumbers a finite‐element method is used to obtain a solution for the secondary electromagnetic fields. The finite element uses exponential elements to efficiently model the fields in the far‐field. In combination with an iterative solution for the along‐strike electromagnetic fields, this produces a considerable reduction in computation costs. The numerical solutions for a horizontal electric dipole are computed and shown to agree with closed form expressions and to converge with respect to the parameterization. Finally some simple examples of the electromagnetic fields produced by horizontal electric dipole sources at both the seafloor and air‐earth interface are presented to illustrate the usefulness of the code.

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