Improvement in Characteristics of Microstrip Antenna with the Help of Different Metamaterial Structu

IJIRST –International Journal for Innovative Research in Science & Technology| Volume 1 | Issue 6 | November 2014 ISSN (online): 2349-6010

Improvement in Characteristics of Micro strip Antenna with the Help of Different Meta material Structures Darshansinh N. Patel PG Student Department of Electronics and Communication Engineering Silver Oak College of Engineering & Technology Gujarat Technological University Ahmedabad, India

Mohammed G. Vayada Assistant Professor Department of Electronics and Communication Engineering Silver Oak College of Engineering & Technology Gujarat Technological University Ahmedabad, India

Vimal H. Nayak Assistant Professor Department of Electronics and Communication Engineering Silver Oak College of Engineering & Technology Gujarat Technological University Ahmedabad, India

Abstract In this paper we have discussed about different metamaterial structures. Metamaterial structures are artificially designed materials to provide properties that are not readily available in nature. The size minimization & high bandwidth of microstrip antenna plays important role in the development of communication systems. These characteristics can be obtained by the help of this artificial metamaterial structures like split ring resonator (SRR), complementary SRR, Defected ground structures etc.

Metamaterial structured microstrip antenna exhibits negative permeability & permittivity which results into enhancement in antenna parameters like return loss, bandwidth, directivity, antenna gain etc. In this paper we have also discussed about different properties of metamaterial structure.

Keywords: High gain antennas, Metamaterial structure, Microstrip antenna, Split ring resonator, Defected ground structure _______________________________________________________________________________________________________

I. INTRODUCTION In Metamaterial structure the structural properties of a material were manipulated, new material were formed with unusual properties which leads to improvisation in characteristics of microstrip antenna. Therefore metamaterials are materials organized at structural level. Veselago in his early work put forward a theoretical speculation of materials having both negative electric permittivity and magnetic permeability negative in the same frequency band[2]. Smith et al and Pendry in 2001 experimentally prove the work of Veselago. Metamaterials are characterized as having backward wave, negative refractive index and inverse Snell‟s law of refraction. This unusual electromagnetic properties has attracted many researchers to turn their attention to this novel research work.

II. METAMATERIAL We can separate the Metamaterial that are artificially designed dielectrics--typically periodic in nature-into two main categories: (i) those which are having unit cell sizes that are small comparable to the wavelength ( λ/10 ) and display single-negative material SNG or double-negative material DNG characteristics; (ii) the periodic structures whose unit cell dimensions are in the order of λ -typically in the range of λ/2-and which are also known as electromagnetic bandgap EBG materials[5].

A. Classification of Metamaterial There are four types of Material as shown in table.

Permittivity >0 <0 >0

Table 1 Types of material Permeability Material µ >0 Double positive material (DPS) µ >0 Epsilon negative material (ENG) µ <0 Mu negative material (MNG)

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Improvement in Characteristics of Micro strip Antenna with the Help of Different Meta material Structures (IJIRST/ Volume 1 / Issue 6 / 043)

<0

µ <0

Double negative material (DNG)

Where, DPS-Double positive material, ENG-Epsilon (electrically) negative material, MNG-Mu(magnetically negative material, DNG-Double negative material A medium having both permittivity & permeability greater than zero ( > 0, μ > 0) are known as double positive (DPS) material. Most occurring media (e.g. dielectrics) fall under this type of material. A medium having permittivity less than zero & permeability greater than zero ( < 0, μ > 0) are known as Epsilon negative (ENG) material. In certain frequency ranges many plasmas exhibit this characteristics. A medium having both permittivity greater than zero & permeability less than zero ( > 0, μ < 0) are called as Mu negative (MNG) material. In certain frequency ranges some gyro tropic material exhibits this characteristic.

A medium having both permittivity & permeability less than zero ( < 0, μ < 0) are called as Double negative (DNG) material.

This DNG class of material not found in nature but physically realizable [5].

B. Negative Refraction Metamaterials are also called as left handed metamaterial[6].Figure 1 shows the refraction in left handed metamaterial & conventional material. Metamaterials have negative refractive index which is a reversal of Snell‟s law, hence called as negative index materials [6]. Negative refraction can be achieved when both and are negative, as described in the following equations [4]. √ √ =√ =√ = -1√

<0

Fig. 1: Negative Refraction

C. Realization of Metamaterials One of the most commonly used Metamaterial structures is a dense array of thin wires. Thin metallic wires are arranged periodically with an array of split-ring resonators (SRRs) are arranged periodically [5]. If the operating frequency is lower than the cut-off frequency of an array („plasma frequency‟), the equivalent effective permittivity is negative (ENG). On the contrary, effective permittivity is positive above the plasma frequency (EPS)[5].

Fig. 2: Synthesis of Double Negative Material (DNG)

D. Split Ring Resonator (SRR) External magnetic field penetrates through the rings and currents are induced [7]. Gap prevents currents from flowing around the ring, which results in significant increase in the resonance frequency of the structure [3]. SRR provides a resonant structure which is much smaller than the resonance wavelength.

Fig. 3: Structure of SRR

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Improvement in Characteristics of Micro strip Antenna with the Help of Different Meta material Structures (IJIRST/ Volume 1 / Issue 6 / 043)

E. Complementary SRR Complementary SRR is also possible to design [4]. The complementary split ring resonator structure is obtained by replacing the copper parts with substrate material and substrate material with copper parts [3]. Different Shapes of Complementary SRR shown in figure 4.

Fig. 4 Single complementary SRR structure of the antenna design with 4 different shapes â&#x20AC;&#x201C; square, circular, triangular and rhombic

F. Defected Ground Structure The figure shows front view and back view of metamaterial antenna with I-shaped defected ground structure at ground layer of microstrip antenna [8]. The shown design works for S-band and operates at 2.45GHz. The DGS structure results in improvement of gain with 17.6% and return loss with 71.89% compare to conventional antenna. Also reduce the size of radiating patch reduced about 21% compare to conventional antenna [8].

Fig. 5: Front view Microstrip antenna with I-shaped DGS

Fig. 6: Back view of I-shaped defected ground structure (DGS) Table 2 Dimensions of DGS structure Parameters Dimensions (mm) a 9 b 8 c 9 Ws 39.65 Ls 47.8 Table 3 Comparison between Metamaterial & Conventional Antenna Results Parameters Metamaterial Antenna Conventional Antenna Percentage Difference(%) Return Loss S11(dB) -45.54957 -26.49887 71.89 Bandwidth (MHz) 34.860 15.979 118.16 Gain(dB) 5.41 4.6 17.60 38.7x30 42.9x34.67 20.73 Patch Area (

G. EBG Structure The figure shows front view and back view of metamaterial structured antenna with Electromagnetic Band Gap (EBG) structures at the ground plane [1]. The shown design operates at 7.3 GHz As a result of combining the rectangular patch with EBG structure, the bandwidth of the antenna has been increases by 39.63% and antenna size reduced by 22.38% compared to the antenna without EBG [1]. The return loss also met the specification of -10 dB cut off.

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Improvement in Characteristics of Micro strip Antenna with the Help of Different Meta material Structures (IJIRST/ Volume 1 / Issue 6 / 043)

Fig. 7: Front View microstrip antenna with EBG

Fig. 8: Periodic structure of the square hole (EBG structure) Table 4 Dimensions of EBG structure Parameters Dimensions (mm) W 4.8800 G 2.8000 g2 5.3885 g3 2.8395 Ws 31.017 Ls 25.919 Table 5 Comparison between Metamaterial (with EBG) & Conventional (without EBG) Antenna Results Parameters Metamaterial Antenna (with EBG) Conventional Antenna(without EBG) Percentage Difference(%) Return Loss S11(dB) -43.47811 -27.21667 59.7 Bandwidth (MHz) 226.2 162 39.63 14.53x8.95 14.53x11.53 22.38 Patch Area (

III. MICROSTRIP ANTENNA DESIGN A. Dimension of patch width â&#x2C6;&#x161;

B. Effective Dielectric constant [

]

C. Length Extension

D. Patch Length â&#x2C6;&#x161;

After calculations of above equations we will get length and width of microstrip antenna [1]. Then after antenna design can be realized.

IV. CONCLUSION In this paper we have discussed different metamaterial structures and also discussed properties of metamaterial structure. We have seen basic antenna design calculations. From the analysis of different metamaterial structure we have seen that

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Improvement in Characteristics of Micro strip Antenna with the Help of Different Meta material Structures (IJIRST/ Volume 1 / Issue 6 / 043)

metamaterial structured microstrip antenna has enhancement in antenna parameters like return loss, bandwidth, directivity, antenna gain etc.

In the future scope of work, the antenna design can be made by using the N-number of SRR rings, adding the array of defined metamaterial structure or define the new design of SRR as superstrate layer will met better improvement in antenna characteristics.

REFERENCES [1] [2] [3] [4] [5] [6] [7] [8]

Nabilah Ripin, Robi‟atun Adayiah Awang, Ahmad Asari Sulaiman, Noor Hasimah Baba, Suhaila Subahir,“Rectangular Microstrip Patch Antenna with EBG Structure,” IEEE Student conference on research & development,2012.

V.G Veselago, “The electrodynamics of substances with simultaneously negative values of and µ”, sov. Phys. Vol. 10, no.4, 509-504, February, 1968 Daniel R. Luna, Valdemir P. Silva Neto, Cristhianne F. L. Vasconcelos, and Adaildo G. D‟Assunção,“Microstrip Patch Antennas with Metamaterial Inspired Substrates and Superstrates,” IEEE 2013,Department of Communication Engineering, 59078-970 Natal, RN, Brazil H.Nornikman,B.H.Ahmad,M.Z.A.Abd Aziz,A.R.Othman,“Effect of Single Complimentary Split Ring Resonator Structure on Microstrip Patch Antenna Design” IEEE symposium on wireless technology & applications, Sept 23-26,2012.

Wojciech J. Krzysztofik,“Antenna Properties Improvement by Means of Modern Technology,” IEEE Microwaves, Radar and Wireless Communication(MIKON) International Conference on June 16-18,2014.

Bashir D. Bala1, Mohamad Kamal A. Rahim2, N. A. Murad3,“Bandwidth Enhanced Microstrip Patch Antenna Using Metamaterials,” 2012 IEEE AsiaPacific Conference on Applied Electromagnetics (APACE 2012), December 11-13, 2012, Melaka, Malaysia.

Walaa Wahba, Mahmoud A. Abdalla, and Ahmed A. Nazir Mohamed “A Uni-Planar Microstrip CSRR metamaterial Antenna” IEEE 2014, Electromagnetic Fields Group, MTC College University Cairo, Egypt.

N. Ripin, S. N. C. Yusoff, A. A. Sulaiman, N. E. A. Rashid, M. F. Hussin,“ Enhancement of bandwidth through I-Shaped Defected Ground Structure,” IEEE International RF and Microwave Conference, December 9-11,2013 Penang,Malasiya.

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