# Magnetic Field Theory Research Paper

838 Words4 Pages
Finite Difference Time Domain
Electromagnetic field theory is a theory that explains the relationship between an electric field and a magnetic field, causing the electromagnetic wave propagation. This theory was proposed by James Clark Maxwell in 1865. According to Maxwell, the electric field that changes will give rise to a magnetic field. Meanwhile, Faraday argued that the change in the magnetic field induce an electric field. Thus, the relationship between an electric field and a magnetic field causes an electromagnetic wave. It can be said that the electromagnetic wave is the wave blend between electric fields with magnetic fields caused by electrical charges move accelerated.
The finite-difference time-domain (FDTD) is a computational
…show more content…
For instance in vacuum, the phase velocity of the numerical wave modes in the FDTD mesh can be different from vacuum speed of light. In fact the phase velocity of the numerical wave modes is a function of wavelength, the size of the cells and the direction of propagation. This numerical dispersion can carry to non-physical output such as dilatation of single-pulse waveforms, imprecise canceling of multiple scattered wave and pseudo refraction . It is described that to limit the amount of numerical dispersion, the size of each cell must be at least ten times smaller than the shortest wavelength that propagate on a space grid. Of course the numerical dispersion will be reduced even further if smaller cell size is used. However using a smaller cell size will increase the number of cells needed to fill the space grid and causes increase computational demand and time of the model. Where λo is the operating wavelength, the rule…show more content…
Sources are characterized according to their shape or FDTD implementation. A source can formed of sinusoidal or Gaussian pulse. A Gaussian pulse is desirable as the excitation because its frequency spectrum is also Gaussian and will provide frequency-domain information from dc to the highest frequency that will propagate in the numerical lattice. Usually, a Gaussian Pulse is used to represent the PD source. Gaussian pulse could be form in certain frequency that shown in Figure II 17. Figure II 17 Gaussian pulse as source in several frequency

Absorbing boundary condition
Absorbing boundary conditions are needed to keep E and H fields not being reflected back into the space grid. This matter can be solved by applying Perfect Matched Layer (PML). PML is a technique of free-space simulation for solving unbounded electromagnetic problems with FDTD method. As regards PML, it introduces additional unphysical quantities and encompasses a few FDTD layers, shrinking the effective volume of a scenario. However, the advantage of PML is that it is not so much angle-dependent and can be placed close to radiating sources without the risk of instability. The PML concept is shown in Figure II 18. Figure II 18 The PML Concept that shown no reflection on the outer layer

In this thesis, the FDTD calculation would be done by using electromagnetic simulation software which