Study and Comparison of RCS of Microstrip PatchAntennas on LiTi-Ferrite Substrate

Naveen Kumar Saxena', Nitendar Kumar' and P.K.S. Pourush'

I Microwave Lab, Department of Physics, Agra College AgraPIN 282002 (V.P) India. Email: Nav3091@rediffmail.com.ppourush@yahoo.co.in

2Solid State Physics Laboratory, Timarpur, Delhi 110007 India. Email: Nitendar@rediffmail.com

Abstract- Radar cross sections (RCS) of rectangular, circularand triangular microstrip patch antennas are presented whichare printed on LiTi ferrite substrate in X-band (8-12 GHz)region. In this paper, we precise the preparation of apolycrystalline LiTi ferrite of 2200 Gauss saturationmagnetization. The comparison of RCS patterns among RPMA,CPMA and TPMA shows the affective study of radar crosssection which differentiates the stealth capacity as well asminiaturization due to the ferrite substrate application.

Index Terms- Substituted ferrite, rectangular patch, circularpatch, triangular patch, X-band frequency range.

I. INTRODUCfION

materials which are used as in both types single andpolycrystalline.

Some novel characteristics of polycrystalline ferrite overnormal dielectric material make it very useful in microwaveantenna applications. Different types of polycrystalline ferriteshave their specific advantages as Li substituted ferrites hashigh dielectric constant, low sintering temperature etc. thanother substituted ferrites. In order to create miniaturization ofantenna geometries, ferrites are suitable. By using ferritematerials, the antenna size reduced considerably along withthe reduction of surface wave excitation and the loss. Theintegration of ferrite technology into microstrip printed circuitantenna has numerous advantages and potential applications[1-4] .

Antenna is one of important microwave device which is thebackbone of communication. In recent years the application ofmagnetic materials increases as per the high frequencyrequirement. Ferrite is one of the important magnetic

In this communication we are presenting a comparison ofrectangular, circular and triangular patch antenna which isprinted on LiTi ferrite substrate in the X-band (8-12 GHz)region. The structural diagrams of rectangular, circular andtriangular patch antennas are shown in fig. 1.

GroundPlane

IFeed Point

IIFig I: Geometry of Rectangular, Circular and Triangular Patch Antenna

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LiTi-ferrite synthesized from the basic components of lithiumferrites In this work a typical composition of LiTi ferrite havingroom temperature magnetization (41tMs) of 2200 gauss (± 5%) &Curie temperature (Tc) of 500 K (± 5%) & synthesized usingsolid state reaction technique (SSRT).

The ingredients required for the preparation of these ferriteswere calculated on the basis of chemical formula. A smallamount of Mn3+ ion was also incorporated in the basiccomposition in order to suppress the formation of Fe2+ ions inthe ferrites and to influence megnetostriction being a John Tellerion [5, 6]. In order to avoid Lithia at high temperatures ofsintering, Bh03 (0.25 wt %) was added as sintering aid [7].Analytical grade chemicals were used for the preparation of thematerial.

The stoichiometric ratio of the chemicals was thoroughlymixed in a polypropylene jar containing the zirconium balls &distilled water was used as a mixing agent. The presintering ofthe mixed powder has been carried out at - 7500C in a boxfurnace and soaking time was kept 4 hours. The sieved materialwas pressed in disk (antenna substrate) and toroidal shapes withthe help of suitable dies and using hydraulic pressing techniqueat pressure of 10 tonlcm2. The substrates and toroidals werefinally sintered at 10500K for four hours. The heating andcooling cycle of the samples was carried out in the airatmosphere of furnace. The sintered sample so obtained wassubjected to cutting, grinding, polishing etc. in order to getspecific size and shape. The important material properties suchas magnetic and electrical properties were studied [8].

II.

III.

SUBSTRATE PREPARATION

ANTENNA STRUCTURE

thickness h = 0.165cm. The resonant frequency of the antennaevaluated by the classical equation as follows.

8.794fr = K V£;

Where

This equation is based on Cavity model. Symbol a, h, Erand fr are radius of the patch, thickness of the patch, dielectricconstant of substrate and resonant frequency of antennarespectively [9, 10].

Rectangular Patch: Here we have patches of dimensions 'a' and'b' is modeled on a LiTi ferrite substrate with dielectric constant= 17.5 and thickness h = 0.165cm.

cf=----­

2a JCEr ~ 1)

This equation is based on Transmission Line model.Symbol 'a',' b', 'h', is the width, length and thickness of thepatch respectively [9, 10].

Triangular Patch: Here we have patches of equilateraldimension's' is modeled on a LiTi ferrite substrate withdielectric constant = 17.5 and thickness h = 0.165cm.

Circular Patch: We have a patch of radius 'r' which is modeledon a LiTi ferrite substrate with dielectric constant = 17.5 and

This equation is based on Cavity model. Here "s" is thelength of the equilateral triangular patch [9, 10].

Table 1: Comparison of structural parameters between RPMA, CPMA and TPMA on LiTi ferrite at 10 GHz.

Parameters Rectangular Circular Triangular

Dimensiona = 0.6975 em

r = 0.2032 em s = 0.2922 emb - 0.2792 em

Effective a = 0.6975 em r = 0.2104 em s = 0.5277 emDimension b - 0.4046 em

Dielectric Const. 17.5 17.5 17.5

Substrate Width 0.165 em 0.165 em 0.165 em

IV. NUMERICAL CALCULATION AND RESULTS

We have developed both the theoretical framework andcomputational simulation of RPMA, CPMA & TPMA. The

Paper Number: ATT-17-5844Paper Topic : Antenna Theory and Techniques

comparison between power loss and radiation power is listed intable 1 and by the help of these parameters and mathematicalsoftware (Mathworks MatLab 7.1), we also compare simulatedplots (Fig: 2, 3, 4) [11].

Table I : Comparison of parameters between RPMA, CPMA and TPMA on LiTiferrite at to GHz.

V. CONCLUSION

Power Loss Radiation Power

Rectangular 0.231 mW 1.3mW

Circular 0.323mW 1.9mW

Triangular O.058mW 0.78mW

300r----~----~---~-____,

It can be concluded from the table 1 and RCS graphs that:

1. In view of power loss and radiation power the performanceof triangular patch antenna is slightly better than rectangular andcircular patch antenna which gives advantage in stealth purpose.

2. On the other hand RCS of triangular patch antenna is alsogives better signal transmission in compare of circular andrectangular patch antenna.

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200

3. If we have comparison between rectangular and circularpatch antenna performance then rectangular patch gives thebetter RCS than circular patch antenna.

150 After discussing all the above results we can conclude that byusing ferrite materials, the RCS of triangular patch antennaenhanced in compare of other geometry. Using ferrite materialthe antenna size reduced considerably along with the reductionof surface wave excitation and the losses.

The integration of ferrite technology into microstripprinted circuit antenna has numerous advantages and potentialapplications.

642

RCS of microstrip rectangular patch antenna

°O'-----~----~---~-----'

50

100

Fig. 2

ACKNOWLEDGEMENT250

200

The authors are grateful to Dr. R Muralidharan, Director "SolidState Physics Laboratory, Timarpur, Delhi" for providingnecessary facilities, encouragement and motivation to carry outthis work.

150REFERENCES

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Pourush P.K.S. et.al. "Microstrip Scanned Array Antenna on YIGFerrite Substrate", Proc. International Symp. On Antennas andpropagation, Japan 2000.Tsang KK and Langley R.I. , "Annular Ring Microstrip Antennas onBiased Ferrite Substrate", Electronic Letters (UK), 1988.Batchelor J.C. and Langley R.I ., "Beam Scanning using Microstrip Lineon Biased Ferrite", Electronic Letters, Vol. 33, 8, 1997.Kumar Dheeraj and Pourush, P.KS., "Circularly Polarized MicrostripTriangular Array on Normally Biased Yttrium Ferrite", Proceedings ofAsia Pacific Microwave Conference, pp.856 Dec. 2004, New Delhi.L G Van Uitert, Proc IRE 44(1956)1294 .A F Paladino, J S Waug & J J Green J Appl Physics 35(1964)3727.Pran Kishan D R Sagar, S N Chatterjee, L K Nagpaul, N Kumar & K KLaroia Adv In Ceramics 16(1985)207.B.s . Randhawa, H'S. Dosanjh, Nitendar Kumar, "Synthesis of LithiumFerrite by Precursor and Combustion Methods: A Comparative Study" ,Journal of Radio Analytical and Nuclear Chemistry, Aug 2007.Balh IJ. and Bhartia P. (1980), Microstrip Antennas, Artech House,Norwood, M.A.C. A. Balanis, Antenna Theory, John Wiley & Sons, Inc, 1997.Jain M.K et al (1993), Numerical Method for Scientific andEngineering Computation, Wiley Eastern Limited, New Delhi.

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642

RCS of microstrip circular patch antenna

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Fig. 3

Fig. 4 RCS of microstrip triangular patch antenna

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350r----~----~---~-___,

Paper Number: ATT-17-5844Paper Topic : Antenna Theory and Techniques