FRACTAL ANTENNA

By

A.SRIRATNA

OVERVIEWѪIntroductionѪWhat is fractal antennaѪGeometry of fractalsѪFractal dipole Antenna-KOCH fractalѪDifferent Fractal LoopsѪApplicationsѪMeritsѪDemeritsѪConclusion

In today world of wireless communications, there has been an increasing need for more compact and portable communications systems. Just as the size of circuitry has evolved to transceivers on a single chip, there is also a need to evolve antenna designs to minimize the size.

Currently, many portable communications systems use a simple monopole with a matching circuit. The fractal antenna not only has a large effective length, but the contours of its shape can generate a capacitance or inductance that can help to match the antenna to the circuit.

INTRODUCTION

FRACTAL‡ “Fractal” means “broken” or “fractured”‡ Derived from the Latin word “fractus”‡Introduced by “benoit Mandelbrot”, a French mathematician in 1975.‡Personalities like D.Hilbert, Helge Von Koch, G.Cantor played an important role.‡ Fractals are geometrical shapes which are self-similar & independent of scale.‡Fractals are complex geometric designs that repeat themselves and are thus “self similar.‡Area directly proportional to perimeter .‡Based on EUCLIDEAN GEOMETRY.

Ѫ The geometry of fractals is important because the effective length of the fractal antennas can be increased while keeping at total area same.

Ѫ The shape of the fractal antenna can be formed by an iterative mathematical process, called as Iterative Function Systems (IFS).

THE GEOMETRY OF FRACTALS

Ѫ The expected benefit of using a fractal as a dipole antenna is to miniaturize the total height of the antenna at resonance. The geometry of how this antenna could be used as a dipole is shown in fig 1. Ѫ The starting pattern for the Koch loop that is used as a fractal antenna is a triangle. From this starting pattern, every segment of the starting pattern is replaced by the generators.

FRACTAL DIPOLE ANTENNAS- KOCH FRACTAL

Fig.1 :Koch curve

Ѫ Resonant loop antennas require a large amount of space and small loops have very low input resistance. ѪA fractal island can be used as a loop antenna to overcome these drawbacks.Ѫ Fractals loops have the characteristic that the perimeter increases to infinity while maintaining the volume occupied.

FRACTAL LOOPS

Ѫ For a small loop, this increase in length improves the input resistance. By raising the input resistance, the antenna can be more easily matched to a feeding transmission line.

Ѫ Fractals have self-similarity in their geometry, this can lead to multiband characteristic antennas.Ѫ A Sierpinski sieve dipole can be easily compared to a bowtie dipole antenna.Ѫ the middle third triangle is removed from the bowtie antenna, leaving three equally sized triangles, which are half the heightof the original bowtie.

MINKOWSKI LOOP

Fig : Sierpinski triangle

FIG: the current distribution in the areas of resonance

Ѫ Military applications Ѫ Custom applications

  Ѫ Extreme frequency range operation Ѫ Compact enough to be mounted in a variety of locations Ѫ Capability for covert operations

APPLICATIONS

Military applications

Ѫ Support full deployment of world`s most advanced wireless technology Ѫ Mobile device configurations made possible low cost performance enhancement for today`s RFID applications Ѫ Communication applications

CUSTOM APPLICATIONS

Ѫ Powerful, versatile and compact ѫ more reliable and lower cost ѫ increased bandwidth and multiband capability

ѫ decrease size load and enable optimum smart antenna technology ѫ minituratization ѫ better input impedance matching ѫ frequency independent  

MERITS

Ѫ Gain loss Ѫ complexity Ѫ numerical limitations

DEMERITS

To get an understanding of the relationship between the performance of the antenna and the fractal dimension of the geometry requires two courses of action. . The first course of action requires that many more examples of fractal geometries are applied to antennas. The second crucial course of action is to attain a better understanding of the fractal dimension of the geometries.

The fractal counterparts of these antennas having a large fractal dimension are more efficient in filling up the space.

CONCLUSION

“ Bandwidth and Q of antennas radiating TE and TM modes.” IEEE transactions on electromagnetic compatibility

FRACTUS, the technology of nature, www.Fractus.Com

Benoit B. Mandelbrot, “The Fractal Geometry Of Nature” W.H.Freeman 1982

REFERENCES

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