Browsing by Subject "Point sources"

Now showing 1 - 3 of 3

Open Access
Analysis of edge waves due to a point source in the presence of a PEC wedge
(IEEE, 2014) Ghassemiparvin, Behnam; Altıntaş, Ayhan
In this paper, we investigate the behavior of the field in the paraxial region of a perfectly conducting wedge and analyze the guiding effect of the wedge. It is observed that as the wedge angle increases, the guidance effect of the wedge decreases and the scattered field in the paraxial region is maximum for the half plane. In addition, interaction of the edge waves with a spherical impedance scatterer is investigated. It is found that for the backscattering case, as the impedance mismatch between the spherical boss and the free-space increases the scattered field due to the boss increases. However for the forward scattering case, impedance of the boss does not affect the scattered field significantly.
Open Access
Negative refraction and subwavelength focusing using left-handed composite metamaterials
(SPIE, 2008-01) Özbay, Ekmel; Aydın, Koray
We review experimental studies performed on left-handed metamaterials (LHM) at microwave frequencies. The metamaterial structure is composed of periodic arrays of split-ring resonators and wire meshes and exhibits a left-handed propagation band at frequencies of negative permittivity and negative permeability. Negative refraction is verified using prism shaped LHM and also by beam-shifting method. Subwavelength focusing of a point source is achieved with a resolution of 0.13λ, through a flat LHM superlens.
Open Access
Thereconstruction quality improvement of holographic stereograms via variable size segmentation
(IEEE, 2010) Şahin, Erdem; Onural, Levent; Kang, Hoonjong
As computer generated holograms becomes more common, the fast computation of holographic interference patterns in digital environment becomes a necessity. Since the computation time of holograms via Fresnel (or Rayleigh-Sommerfeld) diffraction models makes real time applications impossible, the holographic stereograms are developed to be a solution for this problem. Holographic stereograms divide the hologram plane into segments. In phase added stereograms the coordinates of 3D source points are used while calculating the diffraction field. And that enables to calculate the diffraction field with appropriate sized FFTs. Although the phase added stereograms are advantageous in terms of computation time, the quality of the reconstructed three dimensional images may not be satisfactory. The main reason is that the diffraction field of a given point source is approximated as a pure complex sinusuoid in each segment. To increase the reconstruction quality, we propose a method that uses variable sized segments, as opposed to previously developed holographic stereograms that use fixed sized segments. While approximating the diffraction field of a point source, higher frequency regions are covered with smaller segments and lower frequency regions with larger segments. As a result of this, we keep the total number of oscillations of pure sinusoidal waves constant in each segment. The simulations that we carried out for a point source show that we are able to obtain better quality reconstruction with our method. ©2010 IEEE.