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International Journal of Engineering & Technology, 7 (4.36) (2018) 193-196

International Journal of Engineering & Technology

Website: www.sciencepubco.com/index.php/IJET

Research paper

Multi-band hybrid fractal shape antenna for X and K band

applications

Ammar Nadal Shareef 1*, Abbas Abdulhussein Mohammed 2, Amer Basim Shaalan 3

Department of Sciences, AlMuthanna University, Samawa, Iraq.

Department of Sciences, AlMuthanna University, Samawa, Iraq.

Physics Department, Al-Muthanna University, Samawa, Iraq.

*Corresponding author E-mail: ammarnadhal@mu.edu.iq

Abstract

Fractal shapes has unusual properties. These unique features will affect antenna parameters when designed in fractal shapes. Two fractal

shapes combined together to generate new fractal shape dipole antenna. Seirpinski and modified Koch fractal shapes allow this antenna to

operate at too far apart frequencies lies in X and K band. Fractal dimension of modified Koch is found to be 1.08 which led the antenna to

be electrically small. This is explaining the resonant points at higher frequencies. Uniting X and K band in single antenna will make the

possibility of combining the applications of these two bands in one device. Good results have been obtained from calculating antenna

parameters.

Keywords:

1. Introduction

In the past, antennas had simple shape based on Euclidean geometry

and operate on single specific frequency [1]. Its parameters will

change when operating on different frequencies. By the time the

swift growth of the wireless mobile technology, show need to small

wide band and multi band antennas [2]. A multiband antenna is

designed to operate on several bands to avoid using two antennas.

These antennas many times use designs where part of it is active for

one band, and another part is active for other band [3]. Microstrip

patch antenna is a promising choice for the future technology

because of its advantages like light weight and low profile [4-6].

Fractal geometry deals with self-similar shapes that remain

unchanged under different scales [7]. Combine fractal geometry

with electromagnetic theory have led to access of new shapes in

antenna designs [8]. The term fractal antenna is used to describe

those antenna that are based on such mathematical concepts that

enable one to obtain a new generation of antennas with new features

[9].

In this paper, a new fractal shape dipole antenna design is proposed.

The design is created by combining Sierpinski and modified Koch

fractal shapes. New features obtained from this antenna shape. It

exhibits a multiband behavior that is a property of Sierpinski

triangle shape. The principal frequency located at X -band while the

other resonant points located at k-band, which means that the

antenna is electrically small so it operates at higher frequencies.

This property is obtained from modified Koch fractal shape. Good

computation results we get using

commercially available finite element code HFSS [10].

2. Iterated Function System (IFS) and

Antenna Structure

Iterated function systems (IFS) represent a method for constructing

a wide variety of fractal structures [11]. It is based on the use of a

series of affine transformations (w). Mathematically written as:

w (x, y) = (ax+ by+ e, cx+ dy+ f ) (1)

Where, the coefficients (a, b, c, d, e, f) are real numbers responsible

for movement of fractal element. The coefficients (a, d) are

responsible for scaling and (b, c) are responsible for rotation and (e,

f) responsible for linear transmission. The iterated function system

(IFS) of Sierpinski triangle and Koch curve has been published in

literatures vastly [8]. IFS of modified Koch fractal shape that is used

in our model is represented by:

.................... (2)

The generated shape of modified Koch is shown in Fig.1.

194

International Journal of Engineering & Technology

Fig.1. Modified Koch fractal shape

3. Fractal Dimension

Fractal dimension is an infinite dimensions lies between Euclidean

0, 1, 2, and 3 dimensions. It is a measure of how complicated a self-

similar figure is [12]. The in between dimensions are inherent

character of fractal shapes. Fractal antenna parameters are found to

be related to fractal dimension value. Sierpinski triangle fractal

dimension is equal to 1.58 and Koch fractal dimension is 1.26 [13].

Fractal dimension is calculated with the following equation [14]:

(3)

Where N is the number of copies and 1/E is similarity ratio

Modified Koch fractal dimension is calculated using equation (3) to

be 1.08.It is obvious that whenever fractal dimension decrease, the

electrical size of the antenna decrease too which led the antenna to

operate at higher frequency.

4. Results and Discussion

New fractal shape obtained by combining second iteration of

Seirpinski triangle and modified Koch curve. Calculations are done

with HFSS code. Antenna shape is illustrated in Fig.2 and its

feeding configuration by using coupling aperture is illustrated in

Fig.3.

Fig.2. Antenna fractal shape: Second iteration of Seirpinski combined with

modified Koch.

Fig.3. Feed configuration of the antenna.

The calculated return loss which represents the matching points of

the antenna are shown in Fig.4.

Fig.4. Return loss of the antenna.

It is obvious from this figure, the principal frequency located at

9GHz and the other matching points located at frequencies of k-

band. This property of uniting too far apart bands in one single

antenna makes it very useful in future wireless devices.

The resistance of the feed line of the antenna is set to 50 ohm.

Resistance versus frequency is shown in Fig.5.

Fig.5. Resistance versus Frequency.

8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00 24.00 26.00 28.00 30.00

Frequency [GHz]

-40.00

-35.00

-30.00

-25.00

-20.00

-15.00

-10.00

-5.00

0.00

5.00

Return Loss (dB)

8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00 24.00 26.00 28.00 30.00

Freq [GHz]

-300.00

-200.00

-100.00

0.00

100.00

200.00

300.00

400.00

500.00

600.00

Input Imedance

Blue Color (ReZ)

Red Color (ImZ)

International Journal of Engineering & Technology

195

This model of antenna has acceptable values of gain; this is

shown in Figures 6 and 7.

Fig.6. Gain of antenna for the frequencies (9 GHz-21 GHz)

Fig.7. Gain of antenna for the frequencies (22 GHz-30 GHz).

Summary of calculated results obtained include input

impedance, gain, directivity, and efficiency are listed in table 1.

Table.1. antenna parameters.

Efficiency

Directivity (dB)

Gain (dB)

Input

Impedance(Ω)

VSWR

Return Loss (dB)

Frequency (GHz)

99%

9.29

9.22

45

1.29

-17.7

9

95%

9.40

9.08

49.39

1.54

-13.4

17

99%

8.44

8.40

50.15

1.02

-38.3

18

96%

8.55

8.23

49.15

1.43

-15.7

19

97%

9.55

9.29

50.81

1.35

-16.5

21

88%

9.57

8.43

51.78

1.04

-33.5

22.8

89%

8.90

8.04

47.32

1.05

-31.1

25.2

93%

8.14

7.68

33.48

1.56

-13.1

26

73%

11.52

8.57

34.75

1.53

-13.4

27

66%

13.73

9.15

34.73

1.48

-14.1

30

Three directional patterns of antenna are shown in figure 9.

Fig.9. Three dimensional pattern of the antenna.

5.Conclusion

New fractal shape of antenna design has been presented in this

paper. Combine two fractal shapes, Seirpiniski and modified

Koch, has led to generate new features in this antenna model.

IFS of modified Koch is calculated to generate the fractal shape.

Also, fractal dimension of modified Koch is calculated, it is

equal 1.08. Low value of fractal dimension makes the antenna

electrically small and resonate at higher frequencies. The

antenna is operate at too far apart frequencies lies in X and K

band. This could make the potential of combining the

applications of the two bands in one device. Good results

obtained from calculating antenna parameters like gain and

efficiency.

-200.00 -150.00 -100.00 -50.00 0.00 50.00 100.00 150.00 200.00

Theta [deg]

-24.00

-22.00

-20.00

-18.00

-16.00

-14.00

-12.00

-10.00

-8.00

-6.00

-4.00

-2.00

-0.00

2.00

4.00

6.00

8.00

10.00

Gain (dB)

Blak Color (phi=90deg,Freq.=9 GHz)

Blue Color (phi=135deg,Freq.=17GHz)

Red Color (phi=30deg,Freq.=18GHz)

Yellow Color (phi=85deg,Freq.=19GHz)

Green Color (phi=60deg,Freq.=21GHz)

-200.00 -100.00 0.00 100.00 200.00

Theta [deg]

-20.00

-15.00

-10.00

-5.00

0.00

5.00

10.00

Gain (dB)

Black Color (phi=45deg, Freq.=22.8GHz)

Blue Color (phi=60deg, Freq.=25GHz)

Red Color (phi=30deg, Freq.=26GHz)

Yellow Color (phi=25deg, Freq.=27GHz)

Green Color (phi=30deg, Freq.=30GHz)

196

International Journal of Engineering & Technology

References

[1] Lee, Kai Fong. "Principles of antenna theory." Chichester, Sussex,

England and New York, John Wiley and Sons, 1984, 338

p. (1984).

[2] Krzysztofik, Wojciech J. "Take advantage of fractal geometry in

the antenna technology of Modern

Communications." Telecommunication in Modern Satellite,

Cable and Broadcasting Services (TELSIKS), 2013 11th

International Conference on. Vol. 2. IEEE, 2013.

[3] Werner, Douglas H., and Suman Ganguly. "An overview of fractal

antenna engineering research." IEEE Antennas and propagation

Magazine 45.1 (2003): 38-57.

[4] Krzysztofik, Wojciech J. "Modified Sierpinski fractal monopole for

ISM-bands handset applications." IEEE transactions on antennas

and propagation 57.3 (2009): 606-615.

[5] Shareef, Ammar Nadal, Ali A. Seleh, and Amer Basim Shaalan.

"Pentagon Fractal Antenna for Above 6 Ghz band

Applications." International Journal of Applied Engineering

Research 12.24 (2017): 16017-16023.

[6] Fujimoto, Takafumi. "Wideband stacked square microstrip antenna

with shorting plates." IEICE transactions on

communications 91.5 (2008): 1669-1672.

[7] Falconer, Kenneth. Fractal geometry: mathematical foundations

and applications. John Wiley & Sons, 2004.

[8] Krzysztofik, Wojciech J. "Fractal Geometry in Electromagnetics

Applications-from Antenna to Metamaterials." Microwave

Review19.2 (2013).

[9] Krzysztofik, Wojciech J. "Take advantage of fractal geometry in

the antenna technology of Modern

Communications." Telecommunication in Modern Satellite,

Cable and Broadcasting Services (TELSIKS), 2013 11th

International Conference on. Vol. 2. IEEE, 2013.

[10] HFSS, Ansoft Designer. "version 11." Ansoft Corporation, UK.

[11] Kaka, Askander Khalid. "Calculation Methods of the Length,

Area and Volume of Iterated Function System Fractals." Journal

of Koya University 26 (2013).

[12] Bruno, Odemir Martinez, et al. "Fractal dimension applied to plant

identification." Information Sciences 178.12 (2008): 2722-2733.

[13] Li, Daotie, and Jun-fa Mao. "A Koch-like sided fractal bow-tie

dipole antenna." IEEE Transactions on Antennas and

Propagation 60.5 (2012): 2242-2251.

[14] Fernández-Martínez, M., and M. A. Sánchez-Granero. "Fractal

dimension for fractal structures." Topology and its

Applications163 (2014): 93-111.