A. ANCY STEFFINADEVISREEII ECEVVCOE

BY

OBJECTIVE

To provide a study of different fractal antenna with an overview of recent developments

FRACTAL ANTENNA – AN INTRODUCTION Fractal antenna theory – a new area “fractal ” means broken or irregular

fragments “Family of complex shapes that possess an

inherent self similarity or self affinity in their geometrical structure”

Came from unique occurances in nature

FRACTAL ANTENNA

FRACTAL ANTENNA

Suggests some attractive solutions for using single small antenna needed for different frequency bands (multiband operation)

Size, area and mass reduction (miniaturization)

The effective length of the antenna can be increased keeping the total area same

GEOMETRY OF FRACTALS

The shape can be formed by iterative mathematical process called IFS

Based on series of affine transformationsw(x,y) = (ax+by+e, cx+dy+f)○ a,b,c,d control rotation and scaling○ e , f control linear translation

Repeatedly applying W to the previous geometryfractal geometry

A1=W(A0); A2 = W (A1);……..

GEOMETRY OF FRACTALS

IFS generated a sequence that converges to a final image

More no. of iterations increase in effective length decrease in resonant frequency

Fractal geometry used in most of the works:Koch fractalSirepinski fractalKoch island fractal

A four iteration Koch fractal

A three iteration Sirepinski fractal

A three iteration Koch island

HOW MINIATURIZATION ?

Achieving lower fr with reduced length is miniaturization

Fractal geometry comprise larger antenna length in a smaller volume

HOW MULTIBAND OPERATION? A single antenna

operating in two or more freuquency bands multiband operation

Antenna elements operating in different frequency used

In fractal antenna coupling between sharp angles produce different current paths achieving multi band operation

FRACTAL LOOP ANTENNAS

Loop antenna needs more space

Small loop low input resistance-mismatch to the

transmission line

KOCH LOOP•A koch loop can be used loop antenna•Perimeter gets increased maintaining the same volume • less volume required for resonance• input impedance improved

SIREPINSKI MONOPOLE AND DIPOLE

Multiple bands controlled by scale factors Flare angle controls the frequency shift Models developed to predict the performance

FRACTAL ANTENNA ARRAY

Antenna array : to improve the gain Random fractal used to generate array

configuration between periodic and random Low side lobe (feature of periodic array ) Robust (feature of random array) four stage linear Cantor array

CONCLUSION

An overview of fractal antenna theory was presented

Small sized, lo profile and low weight antennas can be developed by using fractal geometries

Being in early stage of development more innovations to come in the future