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Proceedings of Asia-Pacific Microwave Conference 2007 Design Sierpinski Gasket Antenna for WLAN Application C.Z.C.Ghani, M.H.A.Wahab, N.Abdullah, S.A Hamzah, A.Ubin, S.H.Dahlan, A.K.Anuar,K.N.Ramli, M.F.Alwi Department of Communication Engineering (JEP) Faculty of Electrical and Electronic (FKEE) Universiti Tun Hussein Onn Malaysia (UTHM) 86400 Parit Raja Johor Darul Takzim Email: n Abstract-This project mainly discussed on designing and fabricating the antenna using fractal concept to obtain the dual band resonant frequency at 2.4 GHz and 5.8 GHz for Wireless Local Area Network (WLAN) application. The application of fractal geometry can be used to miniaturize the antenna due to their self-similarity and this project focusing on designing the Sierpinski Gasket Antenna for first iteration. The antenna had been simulated using CST Microwave Studio, while the fabricated antenna had been tested using Network Analyzer. The results of both antenna simulation and measurement are in good agreement with the design expectation. The antenna was fabricated on printed circuit board (PCB) using epoxy/ glass (FR- 4) substrate with 30cm by 30cm metallic copper ground plane. Keywords-component; Sierpinski Gasket Antenna, Wireless Local Area Network (WLAN), Self-similarity. I. INTRODUCTION The expansion revolution of wireless communication technologies for recent years has driving the demand of low profile antenna in large variety of applications in communication system. The dual band antennas with small physical size and good performance can be fulfilled to meet those requirements. In order to maintain multiband operation while simultaneously reducing antenna size, the discipline of fractal geometry and antenna theories has been combined. Fractal are a class of shapes that have no characteristic size. Each fractal composed of multiple iterations of a single elementary shape. The iterations can continue infinitely, thus forming a shape within a finite boundary but of infinite length or area. This shows fractal shapes are compact, meaning that they can occupy a portion of space more efficiently than other antenna types. In the previous literature [1] [2], it has been discovered that fractal shapes radiate electromagnetic energy well and also been demonstrated that fractal antennas exhibit compressed resonance and multi-band behavior, which can radiate signals at multiple frequency bands when their impedance properties are compared to those of Euclidean antennas having the same overall size. Most of the previous researchers had investigated the characteristic and the behaviour of the Sierpinski Gasket Fractal antenna as it has been acknowledged for the utilization of the equipment that need to operate at multiband and wideband especially of its advantages in reducing the antenna size and self similarity property. Figure 1. Two approaches for the generation of Sierpinski Gasket Geometry The application of WLAN having dual band frequencies at 2.4 GHz and 5.8 GHz has become vital in today's wireless technology. Subsequently, this application needs an antenna that having high frequency but small size in order to fit in limited space of communication devices. Therefore, the Sierpinski Gasket Fractal Monopole Antenna would be a promising way to achieve the frequency desired. A metallic ground plane is mounted perpendicular to the antenna to generate an image of the monopole so that an equivalent dipole is produced. The increasing popularity of indoor wireless LAN capable of high-speed transfer rate is prompting the development of efficient broadband antennas. Due to increased usage in residential and office areas, these systems are required to be low profile, aesthetically pleasing and low cost as well as highly effective and efficient. Microstrip patch antennas are well suited for wireless LAN application systems due to their versatility, conformability, low cost and sensitivity to 1-4244-0749-4/07/$20.00 @2007 IEEE. IN tiple Copy Approap h Deocifio Aprch

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Page 1: [IEEE 2007 Asia-Pacific Microwave Conference - (APMC 2007) - Bangkok, Thailand (2007.12.11-2007.12.14)] 2007 Asia-Pacific Microwave Conference - Design Sierpinski Gasket Antenna for

Proceedings of Asia-Pacific Microwave Conference 2007

Design Sierpinski Gasket Antenna for WLANApplication

C.Z.C.Ghani, M.H.A.Wahab, N.Abdullah, S.A Hamzah, A.Ubin, S.H.Dahlan, A.K.Anuar,K.N.Ramli, M.F.Alwi

Department of Communication Engineering (JEP)Faculty of Electrical and Electronic (FKEE)

Universiti Tun Hussein Onn Malaysia (UTHM)86400 Parit Raja

Johor Darul Takzim

Email: n

Abstract-This project mainly discussed on designing andfabricating the antenna using fractal concept to obtain the dualband resonant frequency at 2.4 GHz and 5.8 GHz for WirelessLocal Area Network (WLAN) application. The application offractal geometry can be used to miniaturize the antenna due totheir self-similarity and this project focusing on designing theSierpinski Gasket Antenna for first iteration. The antenna hadbeen simulated using CST Microwave Studio, while thefabricated antenna had been tested using Network Analyzer. Theresults of both antenna simulation and measurement are in goodagreement with the design expectation. The antenna was

fabricated on printed circuit board (PCB) using epoxy/ glass (FR-4) substrate with 30cm by 30cm metallic copper ground plane.

Keywords-component; Sierpinski Gasket Antenna, WirelessLocal Area Network (WLAN), Self-similarity.

I. INTRODUCTION

The expansion revolution of wireless communicationtechnologies for recent years has driving the demand of lowprofile antenna in large variety of applications incommunication system. The dual band antennas with smallphysical size and good performance can be fulfilled to meetthose requirements. In order to maintain multiband operationwhile simultaneously reducing antenna size, the discipline offractal geometry and antenna theories has been combined.Fractal are a class of shapes that have no characteristic size.Each fractal composed of multiple iterations of a singleelementary shape. The iterations can continue infinitely, thusforming a shape within a finite boundary but of infinite lengthor area. This shows fractal shapes are compact, meaning thatthey can occupy a portion of space more efficiently than otherantenna types. In the previous literature [1] [2], it has beendiscovered that fractal shapes radiate electromagnetic energywell and also been demonstrated that fractal antennas exhibitcompressed resonance and multi-band behavior, which can

radiate signals at multiple frequency bands when theirimpedance properties are compared to those of Euclideanantennas having the same overall size. Most of the previous

researchers had investigated the characteristic and thebehaviour of the Sierpinski Gasket Fractal antenna as it hasbeen acknowledged for the utilization of the equipment thatneed to operate at multiband and wideband especially of itsadvantages in reducing the antenna size and self similarityproperty.

Figure 1. Two approaches for the generation of Sierpinski GasketGeometry

The application of WLAN having dual band frequenciesat 2.4 GHz and 5.8 GHz has become vital in today's wirelesstechnology. Subsequently, this application needs an antennathat having high frequency but small size in order to fit inlimited space of communication devices. Therefore, theSierpinski Gasket Fractal Monopole Antenna would be a

promising way to achieve the frequency desired. A metallicground plane is mounted perpendicular to the antenna togenerate an image of the monopole so that an equivalentdipole is produced.

The increasing popularity of indoor wireless LAN capableof high-speed transfer rate is prompting the development ofefficient broadband antennas. Due to increased usage inresidential and office areas, these systems are required to below profile, aesthetically pleasing and low cost as well as

highly effective and efficient. Microstrip patch antennas are

well suited for wireless LAN application systems due to theirversatility, conformability, low cost and sensitivity to

1-4244-0749-4/07/$20.00 @2007 IEEE.

IN tiple Copy Approap h

Deocifio Aprch

Page 2: [IEEE 2007 Asia-Pacific Microwave Conference - (APMC 2007) - Bangkok, Thailand (2007.12.11-2007.12.14)] 2007 Asia-Pacific Microwave Conference - Design Sierpinski Gasket Antenna for

manufacturing tolerances [4]. Typically, patch antennas haveshowed a narrowband response implicating low bit ratetransfer. The aim of this project is to design efficient andreliable broadband patch antennas showing signs of directivityleading to adequate area coverage and sufficient bandwidthusage.

II. DESIGN CONSIDERATION

For Sierpinski gasket monopole antenna, the fractalgeometry was printed on the ungrounded dielectric substrate.Then it is placed perpendicular to a ground plane. In thisproject, low dielectric constant substrate, FR-4 is used as thesubstrate material while a copper sheet preferred for theground plane. With few exceptions, most notably exceptionbeing the log-periodic, a single antenna size for eachapplication of frequency band typically uses. This structure,with similarity dimension about 1.58 (log 3 / log 2), is a

common study among researchers in fractal antennas. Thedesign of the antenna started with the basic square patch singleelement operating at 2.4GHz.

Figure 3. Design of the Sierpinski Gasket Fractal Monopole Antenna bysimulation using CST Microwave Studio software

To find the initial value of the antenna, equation (1) willbe applied

2c m2 +mn+n2

3fr(1)

Figure 4. Reflection coefficient, S11 at 2.4GHz and 5.8 GHz

The VSWR illustrated in Figure 5 verifies that the valuesare 1.615 at 2.4 GHz and 1.689 at 5.8 GHz that are a goodresult for antenna design as VSWR < 2 are achieve.

Figure 2. Construction of the Sierpinski gasket monopole antenna(a) initial triangular antenna, (b) pre-fractal monopole after the first iteration

III. RESULTS AND ANALYSIS

A. Simulation Result

Simulation for Sierpinski gasket monopole antenna hasbeen done using CST Microwave Studio Simulation in orderto obtain dual band resonant frequencies at 2.4 GHz and 5.8GHz for WLAN application. The results of the simulationshow that at frequency of 2.4GHz, the reflection coefficient,Sll is -12.57 dB while at frequency of 5.8 GHz is -11.82 dB.The result of the simulation is illustrated in Figure 4 while thedesign of the simulated antenna using CST Microwave Studiois in Figure 3.

Figure 5.VSWR of the simulated antenna at 2.4 GHz and 5.8 GHz

(a) (b)

(a) (b)

-5.

Page 3: [IEEE 2007 Asia-Pacific Microwave Conference - (APMC 2007) - Bangkok, Thailand (2007.12.11-2007.12.14)] 2007 Asia-Pacific Microwave Conference - Design Sierpinski Gasket Antenna for

been achieved. From observation, the results for both antennasimulations and measurements are in a good agreement. TheSmith Chart however observe that the impedance matching isat 75 ohm which is differ from the normalize impedance of 50ohm. This is occurred due to the soldering technique used, theeffect of improper connector and also the interference fromother equipment nearby. The VSWR of the antenna shows thatthe value is 1.583 that is smaller than 2, a good result for theantenna design.

Figure 6. Radiation pattemn at 2.4 GHz

-90

Figure 8. Reflection coefficient, S11 at 2.4GHz

Figure 7. Radiation pattern at 5.8 GHz

TABLE 1. GAIN, DIRECTIVITY AND BEAMWIDTH

Figure 9. Reflection coefficient, S11 at 5.8GHz

Figure 6 and Figure 7 shows the radiation pattern for 2.4GHz and 5.8 GHz. From figure 6 and Figure 7, the value for3-dB beamwidth, gain and directivity was summarized inTable 1. Directivity for both frequency are almost the same, for2.4 GHz the directivity is about 11.08 dBi and 11.31 dBi for5.8 GHz. Frequency 5.8 GHz has higher gain compared to2.4 GHz.

B. Measurement Results

The measurement had been done using Network Analyzer300kHz-8GHz at WARAS laboratory to get the fabricatedantenna results. Figure 8 depicts the reflection coefficient ofthe antenna at frequency of 2.4 GHz and Figure 9 illustratedthe reflection coefficient of the antenna at 5.8 GHz. Theresults show that for frequency 2.4 GHz, -13.084 dB Sll isobtained while for frequency 5.8 GHz -12.588 dB Sll had

rlgure IU. Antenna Smitn tnart

Farftield 't.,tield. f=2. [l * Gain_AbslTheta

Frequency = 2.4

Main lobe magnitude = 10.9 dB

Main Iobe di,edion = 15.0 deg.

Angular,width (3 dB) = 30.3 deg.

Sid. lobe level = -3.7 dB

Phi= 90

90F,.q~ ~ ~~9..,= 5.

Main lobe magnitude = 7.5 dB 120

Main lobe direcion = 10.0 deg.

Angularwidth (3 dB] = 14.7 deg.

Sid. lobe ee = -2.2 dB

FREQUENCY GAIN DIRECTIVITY BEAMWIDTH

(GHz) (dB) (dBi) (degree)

2.4 10.86 11.08 30.3

5.8 11.31 11.31 14.7

30/ ---4 -_30Phi= 90~ Ph' 2707.

11,

90

I

/1 20

150 Ei10

180

Page 4: [IEEE 2007 Asia-Pacific Microwave Conference - (APMC 2007) - Bangkok, Thailand (2007.12.11-2007.12.14)] 2007 Asia-Pacific Microwave Conference - Design Sierpinski Gasket Antenna for

REFERENCES

Figure 11. VSWR of the fabricated antenna

IV. CONCLUSION

The design of a compact fractral antenna is presented and

discussed in this paper. Fractral antenna posses the advantage

of compact size while maintaining the characteristics of a

microstrip antenna. The antenna can be allocated for both

frequencies of 2.4 GHz and 5.8 GHz in small size of wireless

devices

ACKNOWLEDGMENT

The authors would like to thank, Mr Kadir, Mr Azwadi

and Mr Rosli for their help in completing this project. The

authors are grateful to the Wireless and Radio Science Center

(WARAS) of UTHM for giving permission for antenna

measurement using WARAS equipments.

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[2] Simedra, P. (2004). "Design and Implementation of Compact MicrostripFractal Antennas." Project Report. London, Ontario: The University Of

Western Ontario.[3] Tsachtsiris, G.F., Soras, C.F., Karaboikis, M.P. and Makios V.T. (2004).

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[2] [4] Haider, S. (2003). "Microstrip Patch Antennas for BroadbandIndoor Wireless System." Part 4 - Project Report for Department ofElectrical and Electronic Engineering, Auckland: The University ofAuckland.

[5] Mohamad Khairi bin Raimi (2006). "Koch Fractal Dipole Antenna

Design." Kolej Universiti Teknologi Tun Hussein Onn: B. Eng. Thesis.[6] Carlos Puente-Baliarda, Jordi Romeu, Rafael Pous and Angle Cardama,

(1998). "On the Behaviour of the Sierpinski Multiband FractalAntenna", IEEE Transaction on Antennas and Propagation Letters, Vol.46, No. 4.

[7] Manzuila binti Manshordin (2006). "Modified Sierpinski Gasket FractalAntenna Operating at 1800MHz for GSM Application." Kolej UniversitiTeknologi Tun Hussein Onn: B. Eng. Thesis.

[8] Lam, S.C. (1997). "A Steerable Planar Antenna System for WLAN"University of Queensland: B. Eng. Thesis.

[9] Matteo J.A. and Hesselink L. (2005). "Fractal Extension of Near-FieldAperture Shapes for Enhanced Transmission and Resolution." OPTICS

EXPRESS, Volume 13, No. 2, 636 - 647.[10] Balanis, C.A. (1997). "Antenna Theory: Analysis and Design." 2nd ed.

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