Novels diffractive element in the THz waveband offers the potential to realize novel types of devices for communications, sensing, integrated optics, networks, transmission lines, and so on. To this end, diffractive planar elements fabricated on non-flat surfaces make it possible to enrich the "pool of devices" for applications including integrated optics at different waveband, including THz, and to design elements with novel properties and potentials. This can be illustrated most clearly using as an example optical element such as that for optical polychromatic computers. For instance, the diffractive element discussed above can be used as a nonlinear device for polychromatic radiation or multiplexer or a focusing element with selectivity in the multimode regime. Frequency characteristics for such elements are determined by the extent of concavity (convexity) of the surface of the element and by the direction of incidence wave onto it. Therefore, when working on a wavelength λ is not equal to λ0, the position of the focusing area in space (the amount of its displacement) and focusing properties should depend on the direction of incidence of the radiation. Hence, it is possible to distinguish between a signal incident on the "tip" of the element from that falling on its "base," simply by placing radiation receivers at the corresponding points in space. Thus, in this paper we will present detailed simulation results obtained using a parallel FDTD method and the application of the proposed device to focusing and frequency-selective properties of flat conical diffractive elements in THz waveband.
Recent developments in active millimeter/THz waves high-quality 3D real-time imaging for security applications are
discussed. Such type of imaging systems affords a compact, simple, fast and relatively low-cost system.
Mobile wireless networks of the future will be expected to function in highly diverse environments from dense
foliage to dense urban settings. Under these conditions, the phenomenon of multipath fading will be a problem Here we
describe a new technique to eliminate multipath fading in such wireless networks. Our technique is based on a free
parameter in the design of Fresnel zone plate antennas, a type of reference phase. The technique exploits our ability to
control relative phase between desired signals arriving in the antenna beam and of undesired multipath signals coming
from outside of the beam direction. By control over relative phase, we can reduce the degree of fading to arbitrarily
small values.
The mm-wave planar Fresnel Zone Plate (FZP) lens and antenna has the advantage of being a flat construction that is cheap, light, and easy to manufacture and have a low losses power in material. To increase the focusing efficiency, resolving and scanning properties of a flat mm-wave FZP lenses and antennas, to use an antenna surfaces as a radome and to create different shaped radiation patterns the construction of three-dimensional plate: ogival, spherical, parabolic, conical, etc., for the first time were development and investigated both theoretical and experimentally in mm-waves since 1981.
To increase the focusing efficiency, resolving and scanning properties of a flat mm-wave FZP lenses and antennas, and to create different shaped radiation patterns the construction of three-dimensional plate: ogival, spherical, parabolic, conical, etc., for the first time were development and investigated both theoretical and experimentally in mm-waves since 1981. A new possibilities of the diffractional antenna are discussed.
The imaging systems (with the quality of the radioimages `equal' to the optical images of the targets) based on haven't got any analogies in the methods of the `isotropic radiovision' are suggested. The most important fields of applications of this methods are: imaging radar, security systems, custom control systems, AVC and AVI systems.
In this paper, the main properties of quasioptic elements are present. Some practical system based on the elements are discussed. The diffraction quasioptical elements are also used in microwave antennae. Theory and design are discussed along with some experimental and theoretical results.
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