Diffraction from a wedge - TMz case [FDTD simulation]

Here, we demonstrate the diffraction from a wedge when a plane wave with electric field component normal to the surface is impinging on it. The wedge corner acts as a secondary source to generate cylindrically propagating waves which are clearly seen when the scattered field plots on the right is analyzed. The left side of the animation shows the total field where both the scattered and incident fields are plotted together.





Beugung, Difracción, Diffrazione, Kırınım, 回折, Дифракция, Diffractie, Difração, 衍射, Dyfrakcja, Diffraktion, Interferenz, Interferencia

Corner Reflector (FDTD Animation)

Two corner reflectors with two different tilt angles have been simulated for demonstrating their reflection properties. The simulations are rendered using the total-field/scattered-field finite-difference time-domain algorithm. An identical incoming plane wave in the negative vertical direction hits the corner reflectors. Although having different tilt angles, they reflect the incoming way in the same positive vertical direction. Corner reflectors are known to be retro-reflectors and consists of 2 or more mutually perpendicular and intersecting flat surfaces. They automatically reflect the waves back towards to the source. In practice, they are used for calibration purposes (e.g. meteorological radars) and range detection. Also in maritime and air navigation, they are used to mark the desired objects on the radar screen (e.g. buoys, ships, runways etc). Corner reflectors are also used to as safety reflectors for cars, bikes, traffic signs and similar devices. Here, the reflectors are in the passive mode, but can also be used in semi-active mode to enhance the directivity of dipole antennas. Basically, by placing the dipole antenna in front of a corner reflector, the combined corner-reflector dipole antenna has a better directivity.

Lüneburg Dielectric Lens - Propagation Animation (FDTD simulation)

We demonstrate the electric field propagation through one of the well-known inhomogeneous dielectric lens, namely the Luneburg Lens proposed by Rudolf Luneburg in 1944 (R. K. Luneburg, The Mathematical Theory of Optics, Providence, Rhode Island, Brown University Press, 1944). The dielectric permittivity of the Luneburg lens drops from 2 to 1 from its center to the edges via the following formula: epsr(r)=2-(r/Radius)^2. Since the dielectric permittivity is 1 at the edges and slightly increases towards the center, no surface reflection occurs. We have utilized circles to represent the increasing dielectric permittivity of the lens.

In this simulation, propagation through a 10Lambda diameter Luneburg lens is compared against the free space. 2-dimensional Finite-difference time-domain (FDTD) method is utilized for the simulations. A point source is located at the focal point on the surface and once the waves emerge from the other side of the lens, the collimation effect is observed (i.e. cylindrical waves converge to plane waves) where the waves propagate towards the other focal point at infinity.

References:
A. D. Greenwood and Jian-Ming Jin, "A Field Picture of Wave Propagation in Inhomogeneous Dielectric Lenses", IEEE Antennas and Propagation Magazine, Vol. 41, No. 5, October 1999

Standing Wave Patterns in Medium with Multiple Interfaces

The generation of standing wave patterns in a medium with three different dielectric permittivities. The reflection and transmission along the two interfaces are shown. Since there are infinitely many reflections, only the overall left and right traveling and the total waves are shown in the animation. When the total traveling field is plotted in space at different time instants (as in the bottom figure), the standing wave patterns can easily be observed.

For similar animations involving a single interface, see below:



Standing Wave Pattern (SWR) and Propagation in Lossy Medium

Standing Wave Pattern (SWR) and Propagation in a Lossless Medium

Standing Wave Pattern (SWR) and Propagation in Lossy Medium

This animation serves as complementary to a previously uploaded one (http://www.youtube.com/watch?v=s5MBno0PZjE) where the medium were lossless. This time, the medium onto which the wave is impinging is lossy and we demonstrate the time-domain propagation of a uniform plane wave traveling in the +z direction and normally incident on the medium interface (at z=0). Again, only the electric field intensity is shown.

The top figure shows the incident (blue), reflected (red), incident+reflected (teal) and transmitted field in both media. In the bottom figure, the standing wave patterns created in both media are shown. Also, the decaying nature of the electromagnetic wave due to lossy nature of the medium is evident in the lossy medium.

Linear Polarization Animation

Uniform plane wave traveling in the +z direction. The x and y component of the electric fields are in phase thus the polarization of the electric field is constant over all space (linearly polarized).


Also see below:
Oblique Plane Wave Reflection From Half Space
Radiation from a Circularly Tapered Dielectric Waveguide
Right Hand Circular Polarization (RHCP) Animation
Linear Polarization Animation
Left Hand Elliptical Polarization (LHEP) Animation
Standing Wave Pattern (SWR) Animation
Electromagnetic Propagation of UWB Short Pulse in Random Medium 
Half Wavelength Dipole Antenna Radiation 
Dipole Antenna Radiation 
Dish Antenna Animation (Parabolic reflector) 
FDTD Simulation of a Half Convex Lens

Left Hand Elliptical Polarization (LHEP) Animation

Uniform plane wave traveling in the +z direction. The x and y component of the electric fields have a phase shift with results in a elliptically rotating polarization in the left hand direction.


Also see below:
Oblique Plane Wave Reflection From Half Space
Radiation from a Circularly Tapered Dielectric Waveguide
Right Hand Circular Polarization (RHCP) Animation
Linear Polarization Animation
Left Hand Elliptical Polarization (LHEP) Animation
Standing Wave Pattern (SWR) Animation
Electromagnetic Propagation of UWB Short Pulse in Random Medium 
Half Wavelength Dipole Antenna Radiation 
Dipole Antenna Radiation 
Dish Antenna Animation (Parabolic reflector) 
FDTD Simulation of a Half Convex Lens

Right Hand Circular Polarization (RHCP) Animation

Uniform plane wave traveling in +z direction

Also see below:
Oblique Plane Wave Reflection From Half Space

Radiation from a Circularly Tapered Dielectric Waveguide

Right Hand Circular Polarization (RHCP) Animation

Linear Polarization Animation

Left Hand Elliptical Polarization (LHEP) Animation

Standing Wave Pattern (SWR) Animation

Electromagnetic Propagation of UWB Short Pulse in Random Medium

Dipole Antenna Radiation