High Gain Aperture Coupled Patch AntennaJitendra Kumar Saroj', Aruna Rana', Nitin Kathuria', Jitendra Kr. Mishra'

1-3 Dept. of Electronics & Comm., Noida Institute of Engg. & Tech. (NIET), Greater NoidaEmail ids: jitendra.saroj007@gmail.com, arunarana05@gmail.com, nkathuria.niet@gmail.com

Abstract- This paper is intended to build a High GainAperture Coupled Micro-Strip Patch Antenna to improveits radiation performance. The proposed design is based on anew aperture coupling technique in which the slot is fed by amicro strip line coupled to the patch radiators. The patchesare employed to reduce the radiation into the half-space thatthey occupy and increase the radiation in the other half-space. The shape ofthe patch used is very much responsiblefor the radiation pattern in the desired direction. Radiationcharacteristics and bandwidth are also improved bychoosing a suitable combination ofthe shape offeed and slot.Due to this aperture coupling between patch and micro stripslot line, we achieve both improvement in radiation patternand bandwidth. We achieved 0.563GHz of 10 dB bandwidthat 3.6 GHz resonant frequency. This design was simulatedusing HFSS (High Frequency Structure Simulator).

Keywords- Aperture coupled, patches, slot, feed line.

I INTRODUCTION

MICROS TRIP patch antennas (patch antennasexcited by a strip line) have been extensively used inmilitary (aircraft, spacecraft, satellites, and missiles) andcommercial (mobile radio and wireless communicationsystems) applications [I]. These types of patch antennashave numerous promising features, for instance, theyhave light weight, small size, and low cost. In addition,they can be easily integrated with planar and non planarsurfaces and have many degrees of freedom in theirdesign. However, they have significant radiation in someundesired directions which lead to power loss andsignificant back lobes lead to electromagnetic energyexposure for mobile phone users in case of mobilephones. The radiation pattern is very important parameterin antenna design if the specific absorption rate (SAR) isconsidered [2]. Aperture coupling is an indirect method offeeding the resonant patch. It couples the patch with microstrip line through an aperture or the energy ofthe strip lineand it is done via the opening (slot) in the ground planewhich excites the patch. This aperture is usually centeredwith respect to the patch where there is maximummagnetic field. For maximum coupling it has beensuggested that a rectangular slot parallel to the tworadiating edges should be used [6]. Two very similarcoupling mechanisms take place, one between the feedline and the slot and another between the slot and thepatch. Dielectric constant of the substrate used for thefeed should be in the range of 2 to 10. A thinner feedsubstrate results in less spurious radiation from feed lines

but higher loss. Feed line width decides the characteristicimpedance ofthe feed line [3].

There are two approaches: 1) simulation andmeasurement of radiation patterns and 2) observation ofstanding wave distributions. For the above purposes, acell structure is first considered. As shown in Figure. 1,this cell structure consists of one slot and two patches.

According to the operating mechanism described, thespacing between the two patches and the thickness h ofthesubstrate are very significant in affecting the antennaperformance.

II DESIGN & SIMULATION

For designing high gain patch antenna, we used amicro strip line on Roger RT/Duroid5880 substrate ofpermittivity of 2.2 and loss tangent of 0.0009 with sizeE=40x40 mm' and dielectric thickness ofh=0.76 mm and

y

E

5

-D

- c

G

Fig.l Geometry of the proposed patch antenna: (a) Top view (b) Bottom view

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metal thickness is t=0.024mm and size D=40x40mm2andthe width of strip is 2.3mm and length 20 mm and thepatches have length of7.5mm and width of 10mm. Slotline has the length of 25mm and width 1.5 mm. cut fromthe ground.

XYP~I'Q,r,I 11'~

_-------l~1t5~~~1~1

'"Fig. 2 Simulated Return loss

III RESULTS & OBSERVATION

For the study described in this paper, the antenna isexpected to operate within a frequency 5.0 GHz. Theeffective length ofthe slot line is approximately 25mm sothat the peak voltage will be located at the center of theslot. The influence of the thickness on the return loss isshown in Figure. 2. Thickness of slot is 1.5 mm, theantenna resonates at 3.6GHz and the corresponding returnloss is 34 dB and bandwidth is 3.893-3.330=0.563GHz.From the figure3 Peak Directivity is 94.955 and PeakGain is 93.841. In proposed structure decay factor is zeroand FIB Ratio is 1.919 from Figure 4.

The radiation efficiency is 0.98827. The resonantfrequency dependence of the thickness is very similar tothat ofthe position of the patches. These results are due tothe fact that the thickness affects the coupling among theslots, the feed line, and the patches. Figure 4 shows theradiation pattern. Summarizing the effects of the twoparameters, it is found that the spacing affects the frontand back radiation of the proposed slot antenna but thethickness mainly affects its back lobes when the spacing isset. This phenomenon is due to the fact that the spacingmainly affects the standing wave distribution, whereas thethickness mainly affects the couplings between the slotand the patches. The VSWR in figure5 is 1.06 at 3.6 GHzresonant frequency. The former offers differentfront-back radiation ratios, whereas the latter results indifferent shorting characteristics [4]. This result is fullyconsistent with the described mechanism given in SectionII. In addition, we can observe in the proposed designexample that the optimized values for the spacing and thesubstrate thickness should be 20 and 2.3 mm respectively.

IV CONCLUSIONS

This paper has demonstrated by simulations andexperiments a new aperture coupling structure for micro

• Antenna Parameters

lnputs r-v-r-'

Setup Name: Infinile Sphere1

Intrinsic Variation: Freq='5GHz'

Solution: LastAdaptive

Design Variation: NIA

Array Setup: Regular Array

Antenna Parameters:

Quantily Value

Max U 406.88

Peak Direclivity 94.955

Peak Gain 93.841

Peak Realized Gain 51.131

Radiated Power 53.847 IN

Accepted Power 54.487 IN

Incident Power 100 IN

Radiation Efficiency 0.98827

Front 10 Back Ratio UIINF

Decay Factor 0

Fig. 3 Antenna parameters

HFSSDesign1Radiation Pattern

·90

Curve Info

- ISldelobeY(GalnTataljSetup 1 : La5 tAda ptlVe

- ISidelobe'>(DirTota!}Setup1 , LastAdaptive

120

-'50 150

·180

Fig.4 Radiation pattern (gain & directivity)

XYPlol230IH-,-------------------r--:;:-:;:;::----,

It)&]

5H)

Fig.5VSWR

NIET Journal of Engineering & Technology, Vol. 1, Issue 2, 2013 23

strip patch antenna. The new design utilizes two parasiticpatches on the opposite side and along the axis of the slot.This arrangement establishes the aperture electric field inthe slot with standing wave distributions approximately inphase on the same side of the slot but approximately out ofphase in the opposite side. Therefore, a patch antenna canradiate unidirectional with a high front-back radiationratio without using a back cavity or reflecting plate. Themain beam can be set in the desired direction such as in thebroadside direction independent of a slot length. Mostimportantly, as the electrical length of the slot is increased,the radiation strength in the main beam is also increasedbut the side lobe level is reduced. These promisingfeatures allow the proposed micro strip slot antennas tooffer good potential for high gain and low radiation powerloss applications. Additionally, due to the use of a singledielectric layer, the proposed design, compared to a backplate or cavity, can also offer advantages in terms oflightweight, low profile, and compact size.

REFERENCES

[I] Y. Yashimura, "A Microstrip Slot Antenna," IEEE Trans. AntennasPropagation, vol. ap-29, pp. 2-24,jan. 1981.

[2] R. C. Johnson & H. Jasik, Antenna Engineering Handbook,New York: McGraw-Hill, 1984.

[3] Zarreen Aijazl& S.C.Shrivastava"Effect of the Different Shapes:Aperture Coupled Microstrip Slot Antenna" International Journalof Electronics Engineering, 2(1), 2010, pp. 103-1 OS.

[4] Zarreen Aijaz I& S.C.Shrivastava "Techniques to Reduce the BackLobe of Microstrip Slot Antennae" International Journal ofElectronic Engineering Research. ISSN 0975 - 64S0, vol. 2, no. 1(20 I0), pp. IS-22.

[S] Q. Balzano, O. Garay, & T. J. Manning, "Electromagnetic energyexposure of simulated users of portable cellular phone," IEEETrans. Veh.Technol., vol. 44, no. 3, pp. 390-403,Aug. 1995

[6] Pozar, D.M., "Microstrip Antenna Aperture coupled to AMicrostripline", IEEE Trans., vol. 21, January 17 1985.

Jitendra Kumar Saroj received abachelor's degree in Electronics andCommunication Engineering fromGautam Buddha Technical University,Lucknow, Uttar Pradesh, India andpursuing master's degree in VLSIDesign from Mahamaya TechnicalUniversity Noida, Uttar Pradesh,

India.He is working in the area of Analog VLSI Design.His research interest is Microstrip Patch Antenna.

Aruna Rana received a bachelor'sdegree in Electronics andCommunication Engineering fromGautam Buddha Technical University,Lucknow, Uttar Pradesh, India andpursuing master's degree inTelecommunication from Mahamaya

Technical University Noida, Uttar Pradesh, India. Herresearch interest is Antenna Design under Ultra WideBand configuration.

Nitin Kathuria received his B.E.degree in Electronics &Telecommunication from J.T.MahajanCollege of Engineering, under NorthMaharashtra University in 2004, hisM.E. degree in Communication &Information from Griffith University,

Brisbane, Australia, in 2007. He was lecturer withDepartment of Electronics & Communication,Teertahnker Mahaveer University, Moradabad in 2009-10. Presently he is an Assistant Professor in Department ofElectronics & Communication at Accurate Institute ofTechnology & Management Greater NaIDA, UP, India.His research interests include Antenna Design &Microwave Engineering. At present, he is engaged inUltra Wide band Antennas.

Jitendra Kumar Mishra received abachelor's degree in Electronics andCommunication Engineering fromRajiv Gandhi Technical University,Bhopal, MP, India and a master's degreein Electronics and CommunicationEngineering from National Institute of

Technology, Durgapur, India. Currently, he is pursuing hisPh.D. from the Department of Electronics Engineering,Indian School of Mines, Dhanbad. He is working in thearea of optical fiber communication. His research interestis Microwave Photonics. He has published papers inreputed journals as well as in conferences, including theIEEE. Mr. Mishra is a member ofIEEE and OSA . He is afounder member and Vice-President ofIndian School ofMines, OSA Student Chapter .

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