MINIATURISATION OF PATCH ANTENNA USING NOVEL FRACTAL GEOMETRY

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International Journal of Electronics and Communication Engineering & Technology

(IJECET)

Volume 7, Issue 1, Jan-Feb 2016, pp. 63-74, Article ID: IJECET_07_01_007

Available online at

http://www.iaeme.com/IJECETissues.asp?JType=IJECET&VType=7&IType=1

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ISSN Print: 0976-6464 and ISSN Online: 0976-6472

© IAEME Publication

MINIATURISATION OF PATCH ANTENNA

USING NOVEL FRACTAL GEOMETRY

Padmavathi C

Department of Electronics & Communication Engineering, ACED

Alliance University, Bangalore, Karnataka, India

ABSTRACT

In the Field of low profile antenna micro strip patch antennas have

attracted many researchers due to small size and low cost of fabrication. One

of trending member of new designs is Fractal antenna. Fractal shapes are

recursive/repetitive self-similar geometries, due to this self-similarity they can

provide high gain, multiband, wideband solutions and design miniature

antenna. Fractal shapes are widely used in computing, analysis and design;

recent trends suggest positive outcomes of using fractal shapes in

electromagnetics and communication system. In this paper Jerusalem cube

fractal shape is introduced in probe fed conventional patch antenna for L1

band. A dual band antenna resonating at 1.41 GHz (L) and 3.37 (S) GHz,

band is constructed using said fractal shape. The comparison of Return loss,

Gain, VSWR, % miniaturisation and radiation patterns are shown with

conventional patch antenna. Analysis is done on RT duroid 5880 with

dielectric constant εr = 2.2. The novel fractal antenna is designed, simulated

using an soft HFSS 13.0.

Key words: Fractal Antenna, Jerusalem Cube Fractal, Miniaturisation, Patch

Antenna

Cite this Article: Padmavathi C. Miniaturisation of Patch Antenna Using

Novel Fractal Geometry. International Journal of Electronics and

Communication Engineering & Technology, 7(1), 2016, pp. 63-74.

http://www.iaeme.com/IJECET/issues.asp?JType=IJECET&VType=7&IType=1

1. INTRODUCTION

Advancements in Wireless communication have paved the way for many researchers

to make the system smarter and smarter. In most of RF and Microwave applications

antenna plays an important role, As per the IEEE std.145-1983 the antenna is

considered as means for radiating or receiving radio waves. Theoretically they are the

transducers which convert RF signal into Electromagnetic waves and viceversa.

Antenna in early days used to be voluminous and high profile.

Padmavathi C


Technically, the need is for wider bandwidths, higher gain, smaller size and

multiband abilities in antennas. Cost too, is a factor of consideration. Hence low

profiles and less complexity in fabrication are areas of interest in antenna research.

Printed antennas have capabilities of answering all these demands. In addition, printed

antennas can be smaller in size and can be used for smallest applications to the largest

ones. These printed antennas are widely used in mobile and satellite communication,

the patch antenna allows modifications in their design which can make them suitable

for wideband and multiband applications and also help in miniaturisation. These

micro strip patch antenna are light weight, low cost, easy to design / manufacture, on

the other side these antenna are low profile, low power handling capabilities, low

efficiency and are not suitable for high bandwidth applications these limitations is

overcome by Fractal antenna.

The method to design patch antenna with better properties is to use fractal shapes

in design [9]-[12]. Fractal is an object achieved by recursive arrangement of a shape

or pattern keeping it same at every scale, they are space filling contours and offers

longer electrical length in smaller spaces this help in antenna miniaturisation, offering

multiple resonant frequencies. The term fractal means uneven or broken, the

geometries are complex and cannot be defined using Euclidean geometries and

mathematically infinite structure. The conventional methods available for antenna

miniaturisation does not maintain good characteristics after certain percentage of

miniaturisation and losses its performance. Fractals can help enhancing antenna

performance in terms of Gain, Return Loss, Side Lobes Reduction, etc. If we can

prepare an antenna with enhanced transmission / reception of GPS signals, it would

help in betterment of number of devices. The research in Fractal Antennas is still in its

emerging phase.

Very promising results are seen for further studies in enhancement of antenna

characteristics. Along with Gain and Return Loss enhancement, using fractals not

only creates other frequency bands but shifts the original frequency down. This can be

widely utilized in antenna miniaturization. Literature shows more use of Koch and

Sierpinski models of fractal shapes in monopole, dipole and patch antennas. Wide

scope of combining more than one GPS frequency or combine GPS with classical

GSM or ISM application is there using fractal shapes. Some of the fractals like Koch

curve and Sierpinski gaskets are, even at present, widely used to create multiband and

wideband antennas. Using Sierpinski Carpet fractal, up to 14 % of miniaturization in

conventional L1 band antenna (1.575 GHz) was achieved. Up to 19 % of

miniaturization is achieved using another fractal shape of Koch Curve / Koch

Snowflake.

In this paper an antenna which resonates at L5 (1.17 GHz) GPS frequency band is

designed. The primary model for implementing the fractal is designed using

conventional patch antenna designing parameters. The results show clear resonance at

L5 band with positive gain value and a reasonably good radiation pattern. The co-ax

probe feeding method is tested and results are extracted. In this paper a dual band

antenna which resonates at L and S band with Probe fed technique along with up to

20% miniaturization is achieved using Jerusalem Fractal with promising Return Loss

as well as Gain values. Radiation patterns and VSWR plots are also extracted for each

individual antenna.

Miniaturisation of Patch Antenna Using Novel Fractal Geometry


2. MICROSTRIP PATCH ANTENNA

Micro strip patch antenna is a printed metal patch on ground dielectric substrate, patch

radiates depending on its length, width, feed location, gain, radiation pattern,

dielectric constant of substrate. The patch antenna operating frequencies range from

900 MHz or lower to 30-40 GHz and have three layers top metallic layer is the patch

which radiates, bottom metallic layer is the ground, and middle layer is dielectric. The

resonating frequency of antenna depends on length of patch and dielectric constant of

substrate along with other parameter [16].

Figure 1 Micro strip patch antenna

The patch is made of conducting radiating materials such as gold, copper etc. The

Radiating metallic patch and the probe feed lines are usually photo etched on the

dielectric substrate. Micro strip patch antenna radiate mainly because of the fringing

fields effect between the patch edge and the ground plane. For a rectangular patch, the

length L of the patch is usually 0.3333λ0<L<0.5 λ0, where λ0 is the free space

wavelength. The patch is selected to be very thin such that t << λ0 (where t is the

thickness of patch). The height h of the dielectric substrate is usually 0.003 λ0 ≤ h ≤

0.05 λ0. The dielectric constant of the substrate (εr) is typically in the range 2.2 ≤ εr ≤

12.

2.1. Conventional Rectangular Patch – Co-ax Feed

Since the length of the patch and operating frequency has a direct relation, any of

them has to be defined in the beginning. We will try making an Antenna for L5 band

applications i.e. 1.17 GHz of operating frequency. The antenna Design Equations are

f0 = 1.17 GHz

0=c/ 0 = 256 mm

εr = 4.4 for Material FR4

h = 1.56 mm, height of substrate

For Width of Patch,

=

=

= 78.023 mm

For effective relative permitivity in the medium

εreff =

+

Substituting the values we get, εreff =

+

εreff = 2.7+1.52=4.22

Padmavathi C


For the actual wavelength in the medium, λ =

= 124.61mm

Effective length can be found as Leff =

= 62.40mm

Difference due to fringing field can be expressed as

ΔL = 0.412h

= 0.641mm

The actual patch length

L = Leff - 2ΔL = 61.11mm

Ground plane dimensions are

LG = 6(h) + L = 70.47mm, WG = 6(h) + W = 87.38mm

2.2. Simulations of coventional rectangular patch antenna

(a) (b)

(c)

Figure 2 Antenna for L5 Frequency with Co-ax Feed (a) Top view (b) Side view (c) Angular

view



Figure 3 Return loss of the reference antenna for L5

From Fig.3 it is seen that the antenna resonates at 1.172 GHz which is the L5 band

used for aeronautical navigation along with L1 and L2. The return loss value at the

said frequency is less than -35 dB which shows good VSWR.

Figure 4 Gain plot of the reference antenna for L5

From Fig.4 the positive gain value of 1.89 dB is seen.

Figure 5 Radiation Pattern at L5 frequency

Padmavathi C


3. DESIGN OF ANTENNA

3.1. The Jerusalem Cube Fractal

The Fractal Jerusalem curve is not widely used in printed antenna design is mostly

used in 3D modelling. A novel dual band antenna is conceptualised, simulated and

compared using Jerusalem cube fractal shape on patch. The fractal shape is simple

and easy to design compared with other fractals, the fractal shape is made on a square

or a rectangular patch, the whole patch is made into 9 parts and + cross sign is cut out

of the centre square, this is repeated up to number of levels. In this fractal design, a

cross sign is used, the curve is applied at the edges of conventional patch antenna as

slots in shape of cross used in Jerusalem fractal.

Figure 6 Jerusalem Fractal up to three levels

3.2. Dual Band Novel Fractal antenna Design

The specifications of the antenna are given as F0 = 1.57 GHz (L1 Band), resonating

Frequency, εr = 2.2 for Material Rogers RT / Duroid 5880, h = 1.56 mm, height of

substrate, L = 59.1 mm (W=L, since square antenna), length of the edge of square

patch LG = 80 mm (WG = LG), length of the edge of square ground plane, Length of

each segment in Jerusalem Fractal L1 = 10 mm, Feed Location fx = 11 mm from

centre for impedance matching, The width of single side of cross is 3.33mm, the feed

location is 14.6mm to ensure maximum power transfer, and size of slot is cut from the

patch in square of 10mm*10mm

(a)



(b)

Figure 7 (a) Conventional Patch Antenna (b) Jerusalem Slots on Patch Antenna

(a) (b)

(b)

Padmavathi C


(c)

Figure 8 (a) Conventional Antenna (b) Antenna with Jerusalem Slots (c) Patch Antenna using

Jerusalem Fractal as slots

From Fig.9 it reveals the antenna resonates at L (1.412 GHz) band and S (3.377

GHz) band.

Figure 9 Return Loss plot of Jerusalem Fractal Antenna

Figure 10 Gain plot for Jerusalem Fractal Antenna



(a) For 1.412 GHz

(b) For 3.377 GHz

Figure 11 Radiation Patterns at individual resonant frequencies on Jerusalem Fractal Antenna

The radiation patterns show that both the frequencies show symmetric response

over the theta. Only for 3.377 GHz, the Phi = 90 plot is different in nature from others

and shows response similar to an isotropic antenna.

Figure 12 VSWR plot of the Jerusalem Fractal Antenna

The VSWR plot shown above is in synch with the Return Loss plot. Since the RL

value of the first resonant frequency was high, the VSWR plot shows 3.31. However,

for the second resonant frequency, it shows only 1.56 value of VSWR which can be

considered as good.

Padmavathi C


Figure 13 Comparison of Return Loss of Conventional (L1) band and Jerusalem Fractal

Antenna (L and S) band

The return loss plot shows clear shift in frequency from 1.57 GHz of conventional

antenna to 1.412 GHz of Jerusalem fractal. The 1.5 GHz shift in frequency can

provide a miniaturization of considerable level.

Figure 14 Gain comparisons of Conventional Antenna and Jerusalem Fractal

Fig.14 shows that gain value of both the bands is considerably good compared to

that of the conventional antenna.

Table 1 shows the summary of the Return Loss, Gain, and VSWR and

Miniaturization level of both the antennas.

Table 1 Results and Miniaturization of Jerusalem Fractal Antenna

Antenna Type Results

Return Loss

(dB)

Total gain

(dB) VSWR

Miniaturisation

(%)

Conventional Antenna (1.57

GHz) -20.00 7.35 1.5650

0

Jerusalem Fractal Band 1

(1.412 GHz) 5.41 6.42 1.4120

20%

(Dual Band Antenna)

Jerusalem Fractal Band 2

(3.377 GHz) -13.15 4.31 3.3770



4. CONCLUSION

The novel antenna is designed and simulated using HFSS 13.0. Coaxial probe feeding

is used in designing of an antenna. In the paper the dual band antenna resonating at L

and S Band using Jerusalem fractal as slots in patch for miniaturisation is proposed.

The work shows the positive results of using this fractal shape on conventional patch

antenna. The results show that dual band antenna had better gain and improved

miniaturisation characteristics suitable for GPS and navigation applications. There lies

immense scope of trying further various fractal geometries into patch antenna.

Selective geometries cam be evaluated to achieve further better results compared to

present ones. Also, present antennas can be tuned for further optimization of results.

REFERENCES

[1] Indrasen Singh, Dr. V.S. Tripathi, Microstrip Patch Antenna and its Applications-

a Survey, pp. 1595-1599, 2 (5), Int. J. Comp. Tech. Appl., 2011

[2] Waghmare G.B., Bhanarkar M. K., Microstrip Patch Antenna for ISM Band

Application, pp. 1919-1921, 2(7), International Journal on Recent and Innovation

Trends in Computing and Communication, July 2014

[3] Shivanarayan, Shashank Sharma, Babau R Vishvakarma Analysis of Slot Loaded

Rectangular Microstrip Patch Antenna, pp. 424-430, 34, Indian Journal of Radio

and Space Physics, December 2005

[4] S. Maci, G. Biffi Gentili, P. Piazzesi, C. Salvador, Dual-band Slot-loaded Patch

Antenna, pp. 225-232, 142(3), IEEE Proceedings-Microwave, Antennas and

Propagation, June 1995.

[5] Kai-Ping Yang, Kin-Lu Wong, Dual-Band Circularly-Polarized Square

Microstrip Antenna, pp. 377-382, 49(3) IEEE Transactions on Antennas and

Propagation, March 2001

[6] B. Rama Rao, E. N. Rosario, Mohamed S. Mahmoud, Jay I. Simon, Compact Co-

Planar Dual-Band Microstrip Patch Antennas for Modernized GPS, The MITRE

Corporation Technical Papers, October 2009.

[7] Yoonjae Lee, Suman Ganguly, Raj Mittra, Tri-band (L1, L2,L5) GPS Antenna

with Reduced Backlobes, 28th General Assembly of International Union of Radio

Science, URSI- GA, New Delhi, India 2005

[8] John P. Gianvittorio and Yahya Rahmat-Samii, Fractal Antennas: A Novel

Antenna Miniaturization Technique and Applications, pp. 20-36, IEEE Antenna’s

and Propagation Magazine, 44(1), February 2002

[9] D. Fazal, Q.U. Khan, M.B. Ihsan, Use of partial Koch boundaries for improved

return loss, gain and side lobe levels of triangular patch antenna, Electronics

Letters, 48 (15), July 2012

[10] M. Arulaalan, L. Nithyanandan, Analysis of Triangular Microstrip Patch Antenna

With Koch Boundary for WLAN Application, IJRTET, Vol. 11, June, 2014

[11] Kulbir Singh, Vinit Grewal and Rajiv Saxena, Fractal Antennas: A Novel

Miniaturization Technique for Wireless Communications, International Journal of

Recent Trends in Engineering, 2(5), November 2009

[12] A. Janani, A. Priya, Design of E-Shape Fractal Simple Multiband Patch Antenna

for S-Band LTE and Various Mobile Standards, pp. 12-19, 3 (1), International

Journal of Engineering and Science, May 2013.

[13] Abdelati Reha, Ahmed Oulad Said, Tri-Band Fractal Antennas for RFID

Applications, pp. 171-176, 4(4), Scientific Research Academic Publishers,

October, 2013.

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[14] Wael Shalan, Kuldip Pahwa, Multi-Band Microstrip Rectangular Fractal Antenna

for Wireless Applications, pp. 103-106, 3(1), International Journal of Electronics

Engineering, 2011.

[15] Jagadeesha.S, Vani R.M and P.V Hunugund. Self-Affine Rectangular Fractal

Antenna with Uc-Ebg Structure. International Journal of Electronics and

Communication Engineering & Technology, 4(2), 2013, pp. 15-22.

[16] Ayad Shohdy W. Ghattas and Elsayed Esam M. Khaled A Compact Proximity–

Fed Quad Band–Notched Ultra–Wideband Patch Antenna. International Journal

of Electronics and Communication Engineering & Technology, 5(1), 2014, pp.

43-51.

[17] S. Chatterjee and A Bhattacharya Active Rectangular Patch Antenna - A New

Design Philosophy. International Journal of Electronics and Communication

Engineering & Technology, 3(1), 2012, pp. 220-228.

[18] Carles Puente-Baliarda, Jordi Romeu, Rafael Pous, Angel Cardama, On the

Behavior of the Sierpinski Multiband Fractal Antenna, IEEE Transactions on

Antennas and Propagation, 46(4), April, 1998

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MINIATURISATION OF PATCH ANTENNA USING NOVEL FRACTAL GEOMETRY