IJRAR Research Journal · Web viewFractal Antenna with Different Defective Ground Structure (DGS)...

Fractal Antenna with Different Defective Ground Structure (DGS)

Prajakta Madhukar KatkarM.E

Electronics and Telecommunication Department Pune Institute of Computer Technology, Pune, India

________________________________________________________________________________________________________

Abstract : Wireless technology is one of the main areas of research in the world of communication systems . Microstrip antennas are best choice for wireless application because of low weight, easy to fabricate and low cost. But on the other side, less bandwidth and less gain are the disadvantage of microstrip antenna. So major issues for consideration are multiband and wideband operation of antenna. For obtaining multiband and wideband application, there are two different techniques introduced such as fractal geometry and Defective Ground Structure (DGS). In this paper, Fractal antenna with four shape of DGS has been proposed. The antenna designed on FR4 substrate and a height 1.6mm is used. The proposed antenna has been designed and simulated using High Frequency Structure Simulator (HFSS) version 13.0.

IndexTerms – Fractal Antenna, Defective Ground Structure (DGS), Return Loss.________________________________________________________________________________________________________

I. INTRODUCTION

In wireless communication, microstrip patch antenna is very useful because they are small, compatible and low cost. The wireless applications such as IEEE 802.11a, Wi-MAX, HIPERLAN2, DCS, PCS, UMTS, Bluetooth, WLANof IEEE 802.11b/g/h, satellite communication are used. For these requirements, microstrip patch antenna and fractal antenna are used. Microstrip patch antenna designing consideration has four parts i.e., substrate, patch, ground plane, and feeding. But microstrip patch antenna has few disadvantages like poor efficiency, less power handling capacity and narrow bandwidth.

Fractal antenna overcomes the disadvantages of a microstrip patch antenna. The word fractal comes from Latin word “fractus”. Fractal means have broken or fractured. Geometries and dimensions of fractal structures are an important key factor for the operating resonant frequencies. There are properties of fractal antennas like space-filling, self-similarity, fractal dimen -sions. The main advantages of fractals are miniaturization, wideband characteristic, multiband characteristic and better effi -ciency. The type of fractal antennas are Sierpinski Gasket, Sierpinski Carpet, Koch curves, Minkowski, etc.

To improve the performance parameter of fractal antenna like return loss, VSWR, bandwidth, defected ground structure (DGS) can be introduced. [2] DGS also used for reducing the dimension. DGS is an etched periodic or non-periodic cascaded arrangement defect in the ground of a transmission which creates disturbance in the shield current distribution. The various shapes of DGS such as slot, arrow-shaped, dumbbell etc, are used in this project.[5]

This paper proposed four different DGS structures with fractal antenna. Details of simulated and experimental results along with designing parameter of proposed antennas are presented and discussed.

II. DESIGN OF FRACTAL ANTENNA

For designing fractal antenna we used FR4 material as a substrate which has dielectric constant 4.4. To design a fractal antenna following formulae are used:-

Effective dielectric constant:

ε reff=εr+1

2+

εr−12

[1+12h0

w0]−0.5

where ,w0is the width of patch, h0 is the height of the substrate.

Fringing factor:

∆ L0=0.412 h0

(εreff +3)(w0

h0+0.264)

(εreff−0.258)(w0

h0+0.8)

IJRAR1601009 International Journal of Research and Analytical Reviews (IJRAR) www.ijrar.org 25

Calculate the length of patch (L) :Ll=Le−2 ∆ L0

where ,

Le=C0

2 f r √εreff

where ,L1=Patch length

∆ L=extension∈length of fringing

Calculation the width (W 1) :

W 1=C0

2 f r √ 2εr+1

where ,C0=speed of light ∈free space

f r=resonant frequency

Calculation of ground plane:Lg=L1+6 h0

W g=W 1+6h0 Where,

h1=height of substrateL1=length of patchW 1=widthof patch

VSWR (Voltage Standing Wave Ratio) is defined in terms of input reflection coefficient:

VSWR=1+|Γ|1−|Γ|

w here ,

Γ :reflection coefficient

The Bandwidth of antenna is:BW=f H−f L

W h ere ,f H=Upper edge of t heantenna bandwidthf L=Lower edgeof t he antennabandwidth

To measure bandwidth, return loss is should be below -10dB

Using above all formulae rectangular patch antenna is implemented for the frequency f r=3GHz then iterations are carried out simple circular and square shaped. Square shape which tilts 45 degree in circular shape.

Table 1 Design parameter of patch antenna

Parameter ValuesInput Impedance 50Ω

Frequency 3GHz

Dielectric Constant(ε r4.4

Height of substrate(h) 1.6mm

Table 2 Calculated Parameters for patch


Parameter ValuesPatch Width 30.4mmPatch Length 23.43mm

Length Extension (Δ L¿ 0.0736mm

Dielectric Constant(ε reff ) 4.03

Table 3 Calculated Parameters for Feedline

Parameter ValuesLine width (W1) 3.058mmLine Length ( L1) 13.699mm

Table 4 fractal antenna design parameters and Dimensions

Parameters Value(mm)Patch L 23.43mmPatch W 30mm

Height of Substrate 1.6mmDielectric constant 4.4

Substrate length 41mmSubstrate width 40mm

1st Patch corner cut 2.8mm*4.4mm2nd Patch corner cut 1mm*1mm

1st circle radius 8.5mm2nd circle radius 6mm3rd circle radius 3.6mm4th circle radius 2mm

III. SIMULATION AND RESULTS

In simulation process, we go step by step. Here, we start from 0th iteration and goes upto 3rd iteration.

Fig.1. 0th iteration of fractal antenna

Fig.2. Return loss of 0th iteration of fractal antenna


Fig.3. VSWR of 0th iteration of fractal antenna

Fig.4. 1st iteration of fractal antenna

Fig.5. Return loss 1st iteration of fractal antenna

Fig.6. VSWR of 1st iteration of fractal antenna

Fig.7. 2nd iteration of fractal antenna

Fig.8. Return loss of 2nd iteration of fractal antenna


Fig.9. VSWR of 2nd iteration of fractal antenna

Fig.10. 3rd iteration of fractal antenna

Fig.11. Return loss of 3rd iteration of fractal antenna

Fig.12. VSWR of 3rd iteration of fractal antenna

Above diagram shows all the iteration which shows simulation result of return loss and VSWR. From 0 th to 3rd iteration it shows that they are reduces the size and gives the multiband operation. But it resonates at higher frequencies. So we want fractal antenna resonates on both low and high frequency. For this purpose we use Defective Ground Structure. Also, for improvement in bandwidth we use Defective Ground Structure.

Fig.13. Front view of fabricated design of 3rd iteration of fractal antenna

Discussing various shapes of Different Defective Ground Structures (DGS) is as follows:

1. Fractal antenna with Rectangular Slot DGS:


Front View

Back View

Fig.14. Simulated design of Fractal antenna with Rectangular slot DGS

Front View Back View

Fig.15. Fabricated design of Fractal antenna with Rectangular slot DGS

Return loss:

Fig.16. Simulated result of return loss for Fractal antenna with rectangular slot DGS

Fig.17. VNA result of return loss for fractal antenna with Rectangular slot DGS

Table5.Table of return loss for fractal antenna with Rectangular slot DGS


DGS Return Loss ResultSimulated Fabricated

Rectangu-lar slot DGS

8.3GHz=-23.04dB9.7GHz=-18.194dB11.5GHz=-14.78dB14.1GHz=-14.47dB

8.34GHz=-24.60dB9.97GHz=-17.577dB11.59GHz=-16.74dB14.11GHz=-14.69dB

The above table shows the result of simulated return loss and fabricated result on VNA. The rectangular slot DGS gives four resonant frequencies. In rectangular slot DGS, antenna resonates on higher frequencies.

VSWR:

Fig.18 Simulated VSWR of Fractal antenna with rectangular slot DGS

Fig.19 VNA result of VSWR for fractal antenna with rectangular slot DGS

Table6. VSWR for fractal antenna with Rectangular slot DGS

DGS VSWR ResultSimulated Fabricated

Rectangu-lar slot DGS

8.3GHz=1.139.7GHz=1.2811.5GHz=1.4414.1GHz=1.46

8.34GHz=1.169.97GHz=1.3011.59GHz=1.3514.11GHz=1.46

The above table shows the simulated and fabricated result of VSWR. The VSWR should be less than 2 so, this antenna gives VSWR values less than 2.

3D Polar Plot:


Fig.20. 3D polar plot of fractal antenna with rectangular slot DGS

Radiation Pattern:

Fig.21 Radiation pattern of fractal antenna with rectangular slot DGS

The Fig.20 and Fig.21 shows the 3D-polar plot and radiation pattern respectively.

2. Fractal antenna with Arrow-shaped DGS:

Front View

Back ViewFig.22. Simulated design of fractal antenna with arrow-shaped DGS


Fig.23. Fabricated design of fractal antenna with Arrow-shaped DGS

Return loss:


Fig.24. Simulated return loss result of fractal antenna with arrow-shaped DGS

Fig.25. VNA result return loss of fractal antenna with arrow-shaped DGS

Table7. Table of return loss for fractal antenna with Arrow-shaped DGS


Arrow-shaped DGS

5.7GHz=-17.496dB7.9GHZ=-19.629dB8.9GHZ=-17.401dB11.8GHz=-21.31dB14GHz=-17.467dB

5.79GHz=-12.42dB8.04GHz=-21.469dB9.02GHz=-17.322dB12.14GHz=-24.68dB 13.97GHz=18.574dB

Above table shows the simulated and fabricated results of return loss for fractal antenna with Arrow-shaped DGS. This antenna gives five multi-resonant frequencies.

VSWR:

Fig.26. Simulated VSWR result of fractal antenna with arrow-shaped DGS

Fig.27. VNA result of VSWR on VNA of fractal antenna with arrow-shaped DGS

Table8. Table of VSWR for fractal antenna with Arrow-shaped DGS



Arrow-shaped DGS

5.7GHz=1.307.9GHZ=1.238.9GHZ=1.3111.8GHz=1.1814GHz=1.309

5.79GHz=1.648.04GHz=1.179.02GHz=1.3112.14GHz=1.1413.97GHz=1.27

Above table shows the simulated and fabricated results of VSWR for Fractal antenna with Arrow-shaped DGS.

3D-Polar Plot:

Fig.28. 3D- polar plot of fractal antenna with arrow-shaped DGS

Radiation Pattern:

Fig.29. Radiation pattern of fractal antenna with arrow-shaped DGS

Fig.28 and Fig.29 shows the 3D-polar plot and radiation pattern of fractal antenna with arrow-shaped DGS.

3. Fractal antenna with Dumbbell- shaped DGS:

Front View

Back View


Fig.30. Simulated design of fractal antenna with Dumbbell-shaped DGS


Fig.31. Fabricated design of fractal antenna with dumbbell-shaped DGS

Return Loss:

Fig.32. Simulated return loss result of fractal antenna with dumbbell shaped DGS

Fig.33. VNA result of return loss for fractal antenna with dumbbell shaped DGS

Table9. Table of return loss for fractal antenna with Dumbbell-shaped DGS


Dumbbell-shaped DGS

2.3GHz=-12.87dB6.5GHz=-12.39dB7.6GHz=-21.38dB9.3GHz=-23.99dB11GHz=-15.86dB12.1GHz=-18dB

13.8GHz=29.47dB

2.4GHz=-10dB 6.64GHz=-14.41dB7.93GHz=21.115dB9.02GHz=-21.15dB

10.03GHz=24.099dB 12.31GHz=-19.40dB

Above table shows the simulated result and fabricated result of return loss for fractal antenna with Dumbbell-shaped DGS. It gives the six multi-resonant frequencies which mean it has six multiband operations. When we use dumbbell-shaped DGS, it res -onates at both low and high frequencies. Dumbbell- shaped DGS give better result than rectangular slot DGS and Arrow-shaped DGS.

VSWR:


Fig.34. Simulated VSWR result of fractal antenna with dumbbell shaped DGS

Fig.35. VNA result of VSWR for Fractal antenna with dumbbell shaped DGS

Table10. Table of VSWR for fractal antenna with Dumbbell-shaped DGS


Arrow-shaped DGS

5.7GHz=1.307.9GHZ=1.238.9GHZ=1.3111.8GHz=1.1814GHz=1.309

5.79GHz=1.648.04GHz=1.179.02GHz=1.3112.14GHz=1.1413.97GHz=1.27

3D-Polar Plot:

Fig.36 3D-polar plot of fractal antenna with dumbbell shaped DGS

Radiation Pattern:

Fig.37 Radiation pattern of fractal antenna with dumbbell shaped DGS

Fig.36 and Fig.37 show the 3D-polar plot and radiation pattern respectively.

4. Fractal antenna modified ground with L-shaped DGS:


Front View

Back ViewFig.38 Simulated Design of Fractal antenna modified ground with L-shaped DGS


Fig.39. Fabricated Design of fractal antenna modified ground with L-shaped DGS

The L-shaped DGS is used to increases the impedance matching in the UWB frequencies. When two L-shaped DGS placed in ground plane, which moderate the reflection of surface current so, it adjust the antenna impedance and reduces the return loss.[3]

Return Loss:

Fig.40 Simulated return loss result of fractal antenna modified ground with L-shaped DGS


Fig.41 VNA result of return loss on VNA of fractal antenna modified ground with L-shaped DGS

Table11. Table of return loss for fractal antenna modified ground with L-shaped DGS


Modified ground with L-shaped DGS

0.96GHz=-10.01dB15GHz=-12.91dB(ultra-wideband)

1.63GHz=-11.625dB14.34GHz=10.693dB

(ultra-wideband)

Above table shows the simulated results and fabricated results of fractal antenna with modified ground with L-shaped DGS. It gives ultra-wideband operation which operates on 0.96GHz to 15GHz.Because of DGS technique it enhance the band-width which use for high data speed in wireless application.[6]

VSWR:

Fig.42 simulated result of VSWR of Fractal antenna modified ground with L-shaped DGS

Fig.43 VNA result of VSWR on VNA of Fractal antenna modified ground with L-shaped DGS

Table11. Table of VSWR for fractal antenna modified ground with L-shaped DGS


Modified ground with L-shaped DGS

0.96GHz=1.815GHz=1.5

(ultra-wideband)

1.63GHz=1.70814.34GHz=1.852(ultra-wideband)


3D- Polar Plot:

Fig.44 3D-Polar plot of fractal antenna modified ground with L-shaped DGS

Radiation Pattern:

Fig.45 Radiation pattern of fractal antenna modified ground with L-shaped DGS

Fig.44 and fig.45 shows the 3Dpolar plot and radiation pattern of fractal antenna modified ground with L-shaped DGS. In radi-ation pattern, it is omni-directional in H-plane at frequency 3GHz.

.

IV. CONCLUSION

In this paper, we studied four defective ground structures with fractal antenna. There are three DGS on full ground and one modified ground with DGS. It gives multiband operation as well as ultra-wideband operation. The Slot DGS, arrow-shaped DGS and dumbbell-shaped DGS give multiband operation. Slot DGS resonate at only higher frequencies but arrow-shaped DGS and dumbbell shaped DGS resonates at low and high frequencies. The another one DGS is modified ground with L-shaped DGS give ultra-wide band operation which means 3.1GHz-10.6GHz frequency ultra-wideband operates but this an-tenna operates at 0.96GHz-15GHz. The modified ground with L-shaped DGS gives better antenna efficiency (95%) than other three antennas. The proposed antennas are useful for wireless local area application, satellite communication, and military ap -plication.

REFERENCES

[1] Kavita Sharma, Ankush Gupta, “Review Paper on Fractal Patch Antenna”, International Journal of Modern Electronics and Communication Engineering, Vol. 5, Iss.No. 2, March 2017

[2] Mukesh Kumar Khadelwal, Binod Kumar Kanaujia, and Sachin Kumar, “Defectied Ground Structure: Fundamentals, Analy-sis, and Applications in Modern Wireless Trends”, International Journal Of Antenna and Propagation, 2017

[3] Bharti Gupta, Sangeeta Nakhate, Madhu Shandilya, “A compact UWB Microstrip Antenna with Modified Grround Plane For Banwidth Enhancement”, International Journal of Computer Application, Vol 49,July 2012

[4] Contantine A. Balanis, “ Antenna Theory, Analysis and Design”, A John Wiley & Sons, INC., Publication, United State of America, Third edition,2005

[5] Gary Breed, “An Introduction to Defected Ground Strucutures in microstrip Circuits”, High Frequency Electronics, Summit Technical Media LLC, November 2008

[6] Iram Nadeem and Dong-You Choi, “Broadband Printed Antenna with Modified Rectangular Patch and U-Slot in Ground Plane”, Radioelectronics and Communication Systems, Vol.61 , N0. 12, 2018


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