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ABSTRACT In this paper, we have explored a substantial concept to miniaturize of microstrip patch antenna by employing the double negative (DNG) left-handed Metamaterials, which is having a negative dielectric permittivity and magnetic permeability. It is accomplished with the concept of the compensating the phase by using a thin slab of double positive (DPS) material. This DPS material is having the positive dielectric permittivity and magnetic permeability. DNG Metamaterials is used as a substrate of the microstrip patch antenna. By combining the DNG Metamaterials slab with the DPS materials to form a cavity resonator whose dispersion relation is independent of thickness of the slabs but it depends on the ratio of their thicknesses. This cavity constitutes by DPS and DNG material is used as substrate for the designing of microstrip antennas and the DNG material slab is used to compensate the phase of designed microstrip antenna. Keywords:- Microstrip Antenna, Meta-materials, Double Negative Metamaterials

1.INTRODUCTION Recent advancements of the wireless communication technology are towards the miniaturization and compact designs of communication system have been growing. This communication is possible with the help of antenna. So an antenna size is still remains a matter of concern. For a compact designing of any system, the antenna should also compact in dimension. The microstrip patch antennas is widely used in the recent mobile wireless system due to their inherent capabilities such as low profile, conformability in designing, low fabrication cost, mechanical robustness, polarization agility, compatibility easy integration with microstrip circuits/solid state devices and adaptability to active antenna elements [1-2]. The dimension of a microstrip patch antenna is depends on the wavelength of its resonant frequency. There are several other factors to contribute in calculating the dimension of the antenna such as the used substrate material and its thickness. In the variation of substrate dielectric parameter and characteristics impedance, the return loss parameter is shifted from its resonant frequency. Literature results show that the designing of microstrip antenna high dielectric constant substrates shorting walls and using the shorting pins are effective ways for reducing the size. But the cross-polarization effect of these designed antennas is usually very high which may not be suitable for some applications [3-6]. The antenna was designed using an S shape split ring resonators (SRR) as unit cell inclusions in the form of linearly spaced array on a double positive normal dielectric host material substrate. This feeding technique is printed on DPS surface together with radiating element to introduce additional loss on the cost of overall antenna system efficiency. The present paper explores the possibility of miniaturization the microstrip patch antennas using a substrate material that consists of DPS and DNG Metamaterials.

2.PHASE COMPENSATION Latest interest for the designing of the microwave and optical devices with the material having negative permittivity as well as negative permeability because this material is minimize scattering loss effect at high frequencies. These materials are used as a Metamaterials which are classified as the broader class of materials than left-handed medium. These materials enable us to manipulate the dielectric permittivity and magnetic permeability [7-9]. An electromagnetic wave propagating through these materials has a Poynting vector just anti-parallel with respect to its phase velocity vector as demonstrated theoretically by Veselag. The double negative Metamaterials represents a artificial dielectric material which are usually synthesized using periodic structures and exhibits the negative refractive index characteristics (resulted from simultaneous negative permittivity and permeability). These materials have been referred to as left handed materials, Metamaterials and backward wave materials. The DNG material unit cell employs split ring resonators and thin wires because this thin wire structures produce effective negative dielectric permittivity

DESIGN AND ANALYSIS OF MINIATURIZED COMPACT MICROSTRIP PATCH ANTENNA ON A DOUBLE NEGATIVE METAMATERIAL

Shubhi Jain1, Pallav Rawal2, Neeraj Jain3

1,2,3 Department of Electronics & Communication Engineering Swami Keshvanand Institute of Technology, Management & Gramothan, Jaipur

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below the plasma frequency and the split-ring resonators can result in an effective negative permeability for a defined frequency range. Overlaying these two frequency regimes, both the permittivity and permeability are simultaneously negative thus the index of refraction may have negative real value over a pass band region. When this two structures manipulate, the effective permittivity and permeability of these material can be changed separately. Changing in the permittivity and permeability, the position of double negative regime should be controlled. The phase cancellation occurs in the resonance condition when the phase changes of two layers are equal in magnitude but opposite in direction, Thus the condition for resonance does not depend on the thickness of two layers but it depends on their thickness ratio. This conclusion allows us to reduce the total thickness of the resonator and but the required ratio of their thicknesses is kept constant. The important potential application of this concept is the antenna miniaturization [10-11].

3.DESIGN PARAMETER AND SIMULATION RESULT The designing of a microstrip patch antenna by using a left-handed double-negative material as substrate stated earlier. This idea is implanted because when a uniform plane wave is launched in this a medium, it will have a phase velocity direction is just opposite to its Poynting vector. The phase compensations principle is realized by combining the slabs of normal dielectric materials and a Metamaterials with negative permittivity and permeability. The size of radiating edge of the patch is approximately half of the wavelength in free space for the resonant frequency of the cavity. In this configuration, the frequency dependency of the reflection coefficients is not determined by the resonator size, but the frequency dependency of reflection coefficient is depends on the material parameters. This means that we deal with resonance of inclusions (split ring resonator etc.) and not by the cavity resonance (the resonator size can be further reduced if only one separate inclusion is used as resonator). For high frequencies electromagnetic applications, time domain simulation methods are highly desirable for the simulation result, especially when broadband results are needed.

Figure 1: Dimention of S Shaped Structure

An antenna bandwidth is mainly deter-mined by the materials resonance response and not by the antenna size. Design has a significant patch size reduction. In addition, the back lobe radiation is negligible and directivity is comparable to the traditional microstrip antennas, whose substrate is positive. It is observed that the certain designs have a significant patch size reduction and have a negligible back lobe in the radiation pattern. It shows that new kind antennas will get similar radiation patterns to the ones of conventional design. Dimensions of S unit cell arrays and substrate design parameters are shown. It shows miniaturized and compact microstrip antenna designed above homogeneous Double Negative Metamaterials substrate S shaped unit cell are designed. The proposed antenna physically implemented on top of a substrate having Dielectric constant (r) is 4.4 with the substrate thickness 1.6 mm and having Loss tangent of 0.02 using conventional fabrication process.

Figure 2: Finally Fabricated S Shaped Structure (Top Layer)

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Figure 3: Finally Fabricated S Shaped Structure (Ground Layer)

4.COMPARATIVE ANALYSIS A comparative analysis of single negative (SNG) and double negative (DNG) Metamaterials are inherently dispersive. Therefore, for passive Metamaterials, the real parts of the material parameters are most often negative only over a certain band of frequencies and, thus, their values can shift, or vary, significantly with the changes in frequency. As a result, one should, in general, take into account the frequency dependence of such material parameters. Based in the original problem of a dispersive nature, but travelling a somewhat different avenue, are active Metamaterials. These are intended to have the capability to exhibit negative parameters over a somewhat larger band of frequencies.

Figure 4: Return loss v/s frequency

5.CONCLUSIONS The size reduction of microstrip patch antennas using left-handed materials has been achieved through the concept of phase-compensation by implementing a combined DPS-DNG substrate. By employing the substrate partially filled with double negative medium, the dimension of the patch antenna could be significantly miniaturized. Many researchers are trying to improve the performance of microwave, wireless communications, microelectronics and optical devices using these new meta- materials. As the demand for small size, lightweight, and low-cost communication devices continues, the use of low-cost, small-size patch (or microstrip) antennas asserts itself. There are several variables contribute to the resonance frequency of the CSRR. An extensive study of the variable dependence will enable a designer to choose the appropriate CSRR for a particular patch antenna.

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Comparision of calculations and experiments, J Appl Phys 90(2001). [2] Dwivedi Ved Vyas, Kosta Y P and Jyoti Rajiv, Miniaturized Compact Microstrip Patch Antenna Designed on a

Double Negative Metamaterials for RF wireless systems, Proc. International Conference on Recent Advances in Microwave Theory and Applications,pp.83- 88, Nov. 2008.

[3] I. Vendik, O.Vendic, I. Kolmakov and M . Odit, Modelling of isotropic double negative media for microwave applications Opto Electronics Review,vol.14,no.3,pp.179-186,2006.

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[4] V. C. Bengin, V.Radonic and B.Jokanovic, Fractal Geometries of complementary split-ring resonators, IEEE Trans.on Microwave Theory And Techniques, Vol.56, No. 10,pp. 2312-2321, Oct.2008.

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[9] A. Alu, F. Bilotti, N. Engheta and L. Vegni, Subwave-length, Compact, Resonant Patch Antennas Loaded with Metamaterials, IEEE Transactions on Antennas Propagation, Vol. 55, No. 1, January 2007, pp. 13-25.

[10] H. Mosallaci and K. sarabandi, Antenna Miniaturization and Bandwidth Enhancement Using Reactive Impedance Substrate, IEEE Transactions on Antennas Propagation, Vol. 52, No. 9, September 2004, pp. 2403-2414.

[11] T. K. Lo, C. O. Ho, Y. Hwang, E. K. W. Lam and B. Lee, Miniature Aperture Coupled Microstrip Antenna of Very High Permittivity, Electronics Letters, Vol. 33, No. 1, January 1997, pp. 9-10.