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Progress In Electromagnetics Research Symposium Proceedings, Cambridge, USA, July 58, 2010 885

A New Fractal Antenna for Super Wideband Applications

Abolfazl Azari

Young Researchers Club, Isalmic Azad University, Gonabad Branch, Iran

AbstractModern communication systems require small size and wideband antennas. Fractalgeometries have been used to fabricate multi-band and broad-band antennas. In addition, fractalgeometries can be miniaturized the size of antennas.

In this work, I have investigated a new fractal antenna with multi-band and broad-band proper-ties. The proposed design is a loaded the 2nd iteration of a new fractal geometry to a square loopantenna. The simulation is performed via SuperNEC electromagnetic simulator software. Thesimulation results show that the proposed antenna is applicable in 130 GHz frequency range.Radiation patterns are also studied.

1. INTRODUCTION

Antenna plays such an important role in communication systems and one of the main components ofultra wideband (UWB) communication systems is an UWB antenna. UWB communication systemsrequire smaller antennas with more bandwidth, thus the design, simulation and fabrication of these

antennas are very important. This is the cause of widespread research on UWB antennas in recentyears. One of the good solution is using fractal geometry to design of UWB antennas. Applyingfractals to the antenna elements allows for smaller size, multi-band and broad-band properties [14].

Fractals have self-similar shapes and can be subdivided in parts such that each part is a reducedsize copy of the whole. Self-similarity of fractals causes multi-band and broad-band properties andtheir complicated shapes provide design of antennas with smaller size. Fractals have convoluted andjagged shapes with many corners that these discontinuities increase bandwidth and the effectiveradiation of antennas. Fractals can be placed long electrical length in to a small area using theirability of space-filling [59].

Fractals describe by one algorithm or repetitive function, iterating several times that integraldimension does not define for them.

Several wire antenna configurations based on fractal geometries have been investigated includingKoch, Minkowski, Hilbert, and fractal tree antennas in recent years. These antennas have beensimulated using the moment method, as well as fabricated and measured.

In this paper, a new fractal geometry is presented. By applying this fractal generator to squareloop antenna elements, I have achieved a super wideband antenna.

The moment method based electromagnetic simulator SuperNEC has been used for the designand simulation of the proposed antenna. According to the results this new fractal antenna isapplicable in 1 GHz30 GHz. Also, the radiation patterns are studied in multi frequencies.

2. ANTENNA SPECIFICATIONS

The geometric construction of this new fractal curve starts with a straight line, called the initiator,which is shown in Figure 1 (n= 0). This is partitioned in to four equal parts, and the two centricsegments are replaced with three others of the same length which are formed like a trapezoid withthe indentation angle = 60. This is the first iterated version of the new fractal geometry and is

called the generator, which is shown in Figure 1 (n= 1). The process is repeated in the generationof the 2nd iteration, which is shown in Figure 1 (n= 2).Each segment in the first iteration (generator) is 1/4 the length of the initiator. There are five

such segments. Thus for the nth iteration, the length of the curve is (5/4)n.An iterative function system (IFS) can be used to define the generator. The transformations to

obtain the segments of the generator are:

W1 =

1

4 0 0

0 14

00 0 1

W2=

1

4cos60 1

4sin60 1

41

4sin60 1

4cos60 0

0 0 1

W3 =

1

4 0 3

8

0 14

1

4sin60

0 0 1

W4 =

1

4cos60 1

4sin60 5

8

1

4sin60 1

4cos60 1

4sin60

0 0 1

W5=

1

4 0 3

4

0 14

00 0 1

(1)

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Progress In Electromagnetics Research Symposium Proceedings, Cambridge, USA, July 58, 2010 887

To study the radiation pattern, Figure 6 shows radiation patterns for five frequencies including1 GHz, 10 GHz, 20 GHz, 30 GHz, and 35 GHz for thexy,xz, and yz planes.

Figure 4: Real part of the input impedance. Figure 5: Imaginary part of the input impedance.

(a) (b) (c)

Figure 6: (a) Radiation pattern (xy plane). (b) Radiation pattern (xz plane). (c) Radiation pattern (yzplane).

3. CONCLUSION

The concepts of fractals can be applied to the design of ultra wideband antennas. Applying fractalsto antennas allows for miniaturization of antennas with multi-band and broad-band properties.

The proposed design is a loaded 2nd iteration of a new fractal geometry to a square loop antenna.

The proposed structure has a dimensions of 8 8 cm2.The simulated results conducted by the SuperNEC electromagnetic simulator. Due to the simu-

lation results, the proposed design is a super wideband antenna which is applicable for frequenciesbetween 1 GHz30 GHz.

This super wideband antenna is simple to design and easy to fabricate.

REFERENCES

1. Gianvittorio, J. P., Fractals, MEMS, and FSS electromagnetic devices miniaturization andmultiple resonances, Dissertation, University of California, Los Angeles, 2003.

2. Werner, D. H. and S. Ganguly, An overview of fractal antenna engineering research, IEEEAntennas and Propagation Magazine, Vol. 45, 3857, Feb. 2003.

3. Vinoy, K. J., Fractal shaped antenna elements for wide- and multi-band wireless applications,Thesis, Pennsylvania, Aug. 2002.

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4. Gianvittorio, J. P. and Y. R. Samii, Fractal antennas: A novel antenna miniaturization tech-nique and applications, IEEE Antennas and Propagation Magazine, Vol. 44, No. 1, Feb. 2002.

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& Sons, New York, 1990.10. Azari, A. and J. Rowhani, Ultra wideband fractal microstrip antenna design, Progress In

Electromagnetics Research C, Vol. 2, 712, 2008.11. Azari, A., Super wideband fractal antenna design, IEEE MAPE, Beijing, China, 2009.12. Azari, A., A new fractal monopole antenna for super wideband applications, IEEE MICC,

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