scholarly journals Electromagnetic Pulse of a Vertical Electric Dipole in the Presence of Three-Layered Region

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
D. Cheng ◽  
T. T. Gu ◽  
P. Cao ◽  
T. He ◽  
K. Li
Keyword(s):  
Time Domain ◽  
Electric Dipole ◽  
Delta Function ◽  
Observation Point ◽  
Perfect Conductor ◽  
Transient Field ◽  
Planar Surface ◽  
Vertical Electric Dipole ◽  
Trapped Surface ◽  
The Time Domain

Approximate formulas are obtained for the electromagnetic pulses due to a delta-function current in a vertical electric dipole on the planar surface of a perfect conductor coated by a dielectric layer. The new approximated formulas for the electromagnetic field in time domain are retreated analytically and some new results are obtained. Computations and discussions are carried out for the time-domain field components radiated by a vertical electric dipole in the presence of three-layered region. It is shown that the trapped-surface-wave terms should be included in the total transient field when both the vertical electric dipole and the observation point are on or near the planar surface of the dielectric-coated earth.

scholarly journals Electromagnetic Pulse Generated by a Horizontal Electric Dipole over a Perfect Conductor Covered with a Dielectric Layer

2018 ◽  
Vol 17 ◽  
pp. 01010
Author(s):  
Juan Zheng ◽  
Tong He ◽  
Ping Cao ◽  
Zhuhong Lin ◽  
Kai Li
Keyword(s):  
Dielectric Layer ◽  
Electromagnetic Pulse ◽  
Approximate Expression ◽  
Delta Function ◽  
Perfect Conductor ◽  
Transient Field ◽  
Planar Surface ◽  
Horizontal Electric Dipole ◽  
Trapped Surface ◽  
Microstrip Circuit

In this paper, the electromagnetic pulse due to a delta-function current excitation has been derived on the planar surface of a perfect conductor coated by a dielectric layer. The approximate expression of wave component is obtained when both the transmitting source and the receiving antennas are located on the surface of the dielectric. When the thickness of the intermediate layer is subjected to the condition of k1l<<0.6, this physical model is applied to the microstrip circuit. Analysis and computations of the wave components are carried out on the microstrip circuit, including the surface trapped wave vector which had been ignored in former studies. It is shown that the trapped-surface-wave terms should have been taken into consideration as the main contribution in total transient field in the far-field radiations.

scholarly journals Evaluation of the Trapped Surface Wave of a Vertical Electric Dipole Based on Undetermined Coefficient Method in the Presence of N-Layered Region: A Graphical Approach

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Hong Lei Xu ◽  
Ting Ting Gu ◽  
Yong Zhu ◽  
Xiao Wei ◽  
Liang Sheng Li ◽  
...  
Keyword(s):  
Surface Wave ◽  
Electric Dipole ◽  
Observation Point ◽  
Dipole Source ◽  
Graphical Approach ◽  
Vertical Electric Dipole ◽  
Undetermined Coefficient ◽  
Trapped Surface ◽  
Coefficient Method ◽  
Undetermined Coefficient Method

In previous studies, the trapped surface wave, which is defined by the residue sums, has been addressed in the evaluation of the Sommerfeld integrals describing electromagnetic field of a vertical dipole in the presence of three-layered or four-layered region. But unfortunately, the existing computational scheme cannot provide analytical solution of the field in the presence of the N-layered region when N > 4. The scope of this paper is to overcome the limitations in root finding algorithm implied by the previous approach and provide solution of poles in stratified media. A set of pole equations following with explicit expressions are derived based on the undetermined coefficient method, which enable a graphical approach to obtain initial values of real roots. Accordingly, the generated trapped surface wave components are computed when both the observation point and the electric dipole source are on or near the surface of a dielectric-coated conductor. Validity, efficiency, and accuracy of the proposed method are illustrated by numerical examples.

scholarly journals Simulation of the Vertical-Vertical Controled Source Electromagtic Method

2021 ◽  
Author(s):  
Danusa Souza ◽  
Victor Souza ◽  
Marcos Silva
Keyword(s):  
Electromagnetic Field ◽  
Time Domain ◽  
Electric Dipole ◽  
Three Dimensional ◽  
Comsol Multiphysics ◽  
Controlled Source ◽  
Main Application ◽  
Vertical Electric Dipole ◽  
Acquisition Mode ◽  
Complex Geology

<div>Modeling of the Vertical-Vertical Controled Source Electromagtic Method (VVCSEM) on COMSOL Multiphysics. The VVCSEM method is, strictly speaking, an MCSEM (Marine Controlled Source ElectroMagnetic) that uses a vertical electric dipole as source, vertically oriented receivers, and time domain acquisition mode. Its main application is reservoir monitoring, reducing ambiguities encountered by conventional seismic and minimizing exploration risks in fields with complex geology. The present study shows the results of three-dimensional (3D) VVCSEM modeling built in COMSOL Multiphysics, aiming to analyze the electromagnetic field responses in different models and configurations. The VVCSEM proved to be efficient in detecting the proposed resistive anomalies, as expected and described in the literature.</div>

The 2D coastal effect on marine time domain electromagnetic measurements using broadside dBz/dt of an electrical transmitter dipole

Geophysics ◽  
2011 ◽  
Vol 76 (2) ◽  
pp. F101-F109 ◽  
Author(s):  
Mark Goldman ◽  
Eldad Levi ◽  
Buelent Tezkan ◽  
Pritam Yogeshwar
Keyword(s):  
Time Domain ◽  
Electric Dipole ◽  
Field Measurements ◽  
Resolving Power ◽  
Receiver Coil ◽  
Vertical Electric Dipole ◽  
Horizontal Electric Dipole ◽  
Time Domain Electromagnetic ◽  
Actual Field ◽  
Receiver Arrays

Galvanic transmitter-receiver arrays commonly are used in marine controlled-source electromagnetic (CSEM) exploration of electrically resistive targets such as hydrocarbons, gas hydrates, etc. These arrays utilize vertical electric currents and, as a result, are expected to provide better resolving capability for exploring subhorizontal resistive structures than arrays including horizontal coils. If, however, a subseafloor resistive target is located within a transition zone at distances of up to a few kilometers from the shoreline, the 2D sea-coast resistivity contrast significantly affects the resolving capability of the measurements. An extensive multidimensional modeling supported by numerous offshore measurements showed that the inductive array consisting of a horizontal electric dipole transmitter and a broadside vertical magnetic dipole (horizontal coil) receiver exhibits much better resolving power in time domain compared to all other arrays but those with a vertical electric dipole. This effect takes place only if a short offset receiver coil is located between the transmitter dipole and the coast. If the coil is located at the seaside of the transmitter dipole, the signal lacks the resolving capability almost entirely. At large offsets, the resolving capability of the measurements is relatively low at both sides of the transmitter dipole. Although actual field measurements were conducted only to explore a shallow target (fresh subseafloor groundwater body), calculations show that the same phenomenon exists in case of deep targets (e.g., hydrocarbons).

scholarly journals Approximation and analysis of transient responses of a reverberation chamber by pulsed excitation

2020 ◽  
Vol 18 ◽  
pp. 53-73
Author(s):  
Konstantin Pasche ◽  
Fabian Ossevorth ◽  
Ralf T. Jacobs
Keyword(s):  
Spectral Analysis ◽  
Steady State ◽  
Time Constant ◽  
Time Domain ◽  
Linear Time ◽  
System Response ◽  
Transient Field ◽  
Reverberation Chamber ◽  
Transient Behaviour ◽  
The Time Domain

Abstract. Reverberation chambers show transient behaviour when excited with a pulsed signal. The field intensities can in this case be significantly higher than in steady state, which implies that a transient field can exceed predefined limits and render test results uncertain. Effects of excessive field intensities of short duration may get covered and not be observable in a statistical analysis of the field characteristics. In order to ensure that the signal reaches steady state, the duration of the pulse used to excite the chamber needs to be longer than the time constant of the chamber. Initial computations have shown that the pulse width should be about twice as long as the time constant of the chamber to ensure that steady state is reached. The signal is sampled in the time domain with a sampling frequency according to the Nyquist theorem. The bandwidth of the input signal is determined using spectral analysis. For a fixed stirrer position, the reverberation chamber, wires, connectors, and antennas can jointly be considered as a linear time-invariant system. In this article, a procedure will be presented to extract characteristic signal properties such as rise-time, transient overshoot and the mean value in steady state from the system response. The signal properties are determined by first computing the envelope of the sampled data using a Hilbert transform. Subsequent noise reduction is achieved applying a Savitzky–Golay filter. The point where steady state is reached is then computed from the slope of the envelope by utilising a cumulative histogram. The spectral analysis is not suitable to examine the transient behaviour and determine the time constants of the system. These constants are computed applying the method of Prony, which is based on the estimation of a number of parameters in a sum of exponential functions. An alternative to the Prony Method is the Time-Domain Vector-Fit method. In contrast to the first mentioned variant, it is now also possible to determine the transfer function of the overall RC system. Differences and advantages of the methods will be discussed.

scholarly journals Time-Domain Analytical Expression for Near Fields of Arbitrarily Oriented Electric Dipole and Its Application

2017 ◽  
Vol 2017 ◽  
pp. 1-8
Author(s):  
Qian Yang ◽  
Bing Wei ◽  
Xinbo He ◽  
Minghao Gong
Keyword(s):  
Time Domain ◽  
Electric Dipole ◽  
Near Field ◽  
Wide Band ◽  
Frequency Transformation ◽  
Numerical Examples ◽  
Electromagnetic Problems ◽  
Time Frequency ◽  
The Time Domain ◽  
Analytical Expressions

The near fields of electric dipole are commonly used in wide-band analysis of complex electromagnetic problems. In this paper, we propose new near field time-domain expressions for electric dipole. The analytical expressions for the frequency-domain of arbitrarily oriented electric dipole are given at first; next we give the time-domain expressions by time-frequency transformation. The proposed expressions are used in hybrid TDIE/DGTD method for analysis of circular antenna with radome. The accuracy of the proposed algorithm is verified by numerical examples.

On the propagation of a pulse through an antipode

1969 ◽  
Vol 47 (12) ◽  
pp. 1327-1330 ◽  
Author(s):  
James R. Wait
Keyword(s):  
Time Domain ◽  
Pulse Shape ◽  
Dipole Source ◽  
Transient Field ◽  
Idealized Model ◽  
Time Domain Response ◽  
The Time Domain ◽  
Strong Distortion

The time domain response of the fields in the vicinity of an axial caustic is calculated. The idealized model is a spherical concentric cavity with perfectly conducting walls. It is shown that the transient field, in the vicinity of the antipode of a dipole source, exhibits a strong distortion in the pulse shape.

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