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2D SATELLITEANTENNA,FRESNEL LENS AND PYRAMIDS/

ANTENE SATELIT,LENTILE SI PIRAMIDE IN DOUA DIMENSIUNI

One of the applications of this technique is the realisation of Fresnel lenses for astronomical observations at hard X-ray and gamma-ray energies. The Fresnel lens-based system has the potential to image previously unattainable events such as black hole event horizons, line emission from supernovae, and galactic microquasars. Silicon is an excellent choice for the lens material because it has low absorption properties at energies between 1 keV (soft X-rays) and 100 keV (soft gamma-rays). Moreover, silicon naturally lends itself to this application since its index of refraction at X-ray energies is close to that of vacuum. Extreme roughness tolerances (a key issue because of the DRIE step) are not necessary. And of course, one may take advantage of the already existing mature silicon technology.

Fractal antennas have proven to be the first fundamentally important breakthrough in antenna technology in the last half century.

Fractal Antenna Systems’ technology solves complex antenna problems for customers in new ways. This is why those at the forefront of wireless communications—particularly in the military and government sectors—have adopted solutions from Fractal Antenna Systems for their most challenging applications.

Developed over the last 20 years, fractal antennas have proven to be the first fundamentally important breakthrough in antenna technology in the last half century. Simply put, fractal antennas radically alter the traditional relationships between bandwidth, gain and size—permitting antennas that are more powerful, versatile and compact.

Fractal Antenna produces fractal versions of all existing antenna types, including dipole, monopole, patch, conformal, biconical, discone, spiral, helical and others, as well as compact variants of each only possible through fractal technology.

A fractal element antenna is shaped using fractal geometry. A fractal is “self similar”—a complex pattern built from the repetition of a simple shape. The inherent qualities of fractals enable the production of high performance antennas that are typically 50 to 75 percent smaller than traditional ones. Additionally, fractal antennas are more reliable and lower cost than traditional antennas because antenna performance is attained through the geometry of the conductor, rather than with the accumulation of separate components or separate elements that inevitably increase complexity and potential points of failure. The result is one antenna able to replace many.

In addition, Fractal Antenna’s technology affords unique improvements to antenna arrays, increasing their bandwidth, allowing multiband capabilities, decreasing size load and enabling optimum smart antenna technology.

As modern telecommunications extend towards higher frequencies, the advantages of employing RF-MEMS switches, phase shifters, and miniaturized fractal antennas become more significant. The input characteristics of the Hilbert curve fractal antenna can be made frequency agile by incorporating RF switches along its length. In addition, due to the large number of connected segments in this antenna geometry, reconfigurable radiation characteristics can be obtained by adding just a few additional line segments to interconnect these through semiconductor or RF-MEMS switches. The beam peak direction can be shifted by 63° and the beam width can be changed by up to 25° by this approach. An electronically steered antenna with micromachined phase shifters using tunable ferroelectric barium strontium titanate thin film is also discussed. These MEMS-based antenna systems find applications in communications satellites and electronically scanned arrays for space-based radars.

http://www.fractenna.com/index_old.html

The reason why the fractal design of antennas appears as an attractive way to make antennas is two-fold. First because one should expect a self-similar antenna (which contains many copies of itself at several scales) to operate in a similar way at several wavelengths. That is, the antenna should keep similar radiation parameters through several bands. Second, because the space-filling properties of some fractal shapes (the fractal dimension) might allow fractally shaped small antennas to better take advantage of the small surrounding space. Such basic concepts have been already confirmed by the examples you will find here in the Fractal Antennas Gallery.

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