FRACTAL ANTENNAS

Karthikeya . G . S USN:1BM06EC042 Dept. of Electronics and communication B.M.S College of engineering, Bangalore-560019 Email id: karthikeyaglr@gmail.com

OVERVIEW

Introduction

Fundamentals of radiation

Mathematics of fractals

Crux of the story( fractal antennas)

Design of these antennas with examples

Radiation pattern and other parameters

Applications,summary

References

WHY FRACTAL ANTENNAS?

Inspired by nature

Frequency decides the type, size of antenna

Increased expenditure

Heavy congestion in data traffic

Space problems to install larger antennas

Standard frequencies decide the design procedure

Gain optimization not possible

HOW DOES AN ANTENNA RADIATE?

THE TWO FLAVOURS IN ANTENNAS

ELECTRIC DIPOLE MAGNETIC DIPOLE

WHAT DO FRACTALS MEAN??

a rough or fragmented geometric shape that can be split into parts, each of which is (at least approximately) a reduced-size copy of the whole,

Fine structures at arbitrarily small scales

Euclidean geometry’s jargon fails to describe it

It has a self similar structure with a fractional dimension

It has a simple recursive definition

Examples: Mandelbrot set, Koch snowflake, Sierpinski triangle, Lyapunov fractal etc….

SOME IMAGES

MATHEMATICS OF FRACTALS

HOW ARE THEY GENERATED?

Using simple quadratic transformation like Q(z) = z^2+C

Using iterated function system(IFS)……chaos game

Affine transformations(linear+ translation……………Ax+B)

Starting symbol production rules Iterations

PROPERTIES OF FRACTALS

Continuous everywhere

Differentiable nowhere

Dimension greater than 1

Self similar

Parameterizations are difficult to implement

FRACTAL ANTENNAS

A fractal antenna is an antenna that uses a fractal, self-similar design to maximize the length, or increase the perimeter (on inside sections or the outer structure), of material that can receive or transmit electromagnetic radiation within a given total surface area or volume.

HOW DID THEY BECOME MULTIBAND ANTENNAS

EXAMPLES

all these patterns do not qualify to be a radiating structure it depends strongly on the ease of implementation

These examples are very crucial as the design criteria, radiation parameters are all based on them

1.The Koch monopole

Some Performance parameters of Koch antenna

RADIATION PATTERN OF KOCH MONOPOLE ANTENNA

2.Sierpenski gasket dipole

3. Sierpinski fractal antenna 4.Hilbert curve fractal monopole antenna

5. Multi ring fractal antenna 5. Peano fractal antenna

DESIGN AND RETURN LOSS GRAPHS OF A HILBERT FRACTAL ANTENNA WITH VARIOUS ITERATIONS

CONTINUED……………..

RADIATION PATTERNS

ANTENNA TESTING

Dedicated indoor range

Outdoor range

Specialized testing

Feature Advantage Benefit

Wideband Speedy spectrum access

Use of one antenna instead of many

Compact More design and use versatility

Lowers cost

Fractal ground plane Smaller/multiband Greater versatility and new packaging options

Frequency independent

Consistent performance over huge frequency range

Solutions open to unknown options

Low mutual coupling Close packing of antenna

Small arrays with great steerability

Proven products Designed for harsh conditions

In use by military and commercial users

DISADVANTAGES

Heavy computing power need to model these antennas

Higher iteration fractals are difficult to fabricate

Power matching techniques at miniature scale is of paramount difficulty

Expensive for prototyping the design since it is mainly a trial and error process

Various polarization schemes are difficult to implement

SPECIFIC APPLICATIONS OF FRACTAL ANTENNAS

RFID applications

Band pass filter

metacloak

Bluetooth, GSM

Automated meter reading

Satellite radio, navigation systems

Electronic warfare

Fractal antenna system for improved wireless telecommunication

SUMMARY

•Geometry of fractals was investigated•The algorithm to generate fractals was learnt•The fundamentals of radiation was learnt (A classical physics approach)•Combination of both the fields lead to fractal antennas•The benefits ,challenges and disadvantages of these antennas were considered•The manufacturability of fractal antennas was considered•Applications of fractal antennas were considered

REFERENCES

•http://library.thinkquest.org/3493/frames/fractal.html•http://www.ccs.neu.edu/home/fell/COM1201/PROGRAMS/RecursiveFractals.html•http://en.wikipedia.org/wiki/Fractal•http://www.math.lsa.umich.edu/mmss/coursesONLINE/chaos/chaos7/index.html•www.fractus.com•www.fractenna.com•Best, S, (2003). "A Comparison of the Resonant Properties of Small Space-Filling Fractal Antennas". IEEE Antennas and Wireless Propagation Letters 2 (1): 197-200. http://www.physics.princeton.edu/~mcdonald/examples/EM/best_ieeeawpl_2_197_03.pdf.•FRACTAL ANTENNAS Mircea V. Rusu, Physics Faculty, Bucharest University, Roman Baican, Adam Opel AG. Russelheim, Germany, Ioana ENE, University "Politehnica" Bucharest, Romania 9. Generalized Sierpinski Fractal Multiband Antenna Jordi Romeu and Jordi Soler IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 49, NO. 8, AUGUST 2001 10. Performance characteristics of Minkowski curve fractal antennas M.Ahmed and others journal of engineering and sciences, 2006 11. Fractal antennas literature study by Philip Felber