optimization of microstrip antenna characteristics using photonic band gap structure

HCTL Open Int. J. of Technology Innovations and ResearchHCTL Open IJTIR, Volume 3, May 2013e-ISSN: 2321-1814ISBN (Print): 978-1-62776-443-8

Optimization ofMicrostrip AntennaCharacteristics UsingPhotonic Band GapStructureAli. Rostami, Seyed Yousef. Shafieiand Farid. Alidoust [email protected], [email protected] and [email protected]

Abstract

This paper presents a microstrip patch antenna using a pho-tonic band gap (PBG) structure for attaining higher band-width. The photonic periodic structure was considered as cross

shaped, placed on the ground plane. The simulation results fromHFSS Ansoft design showed that surface waves can be suppressedby the periodic structure due to the influence of its forbidden band.As a result, the bandwidth of the proposed antenna was 6.7% higherthan the conventional antenna. Moreover, the values of gain and di-rectivity of antenna were more by adding PBG in comparison withthe values of the antenna alone.

School of Engg. Emerging Technologies, University of Tabriz, Tabriz, IranSchool of Engg. Emerging Technologies, University of Tabriz, Tabriz, IranMechatronics Engg. Department, Tabriz Branch, Islamic Azad University, Tabriz, Iran

Ali. Rostami et al.Optimization of Microstrip Antenna Characteristics Using Photonic Band GapStructure.

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Keywords

Microstrip Antenna, HFSS, PBG.

Introduction

In recent years, there has been a prompt growth in using microstrip antennas indifferent applications such as array antennas, cellular phones, wireless commu-nications and other communication systems, due to its advantages such as lowcost, low profile planar configuration, low weight and capability [1]. A microstrippatch antenna consists of a radiating patch on one side of a dielectric substrateand a ground plane on the other side. So, the design of the patch and substratedirectly affects the antenna results. The propagating waves are submitted torefraction effects due to the dielectric characteristics of that material. Theresonant frequency of the antenna is continuing to propagate in its interior.A part of those waves are just emitted or received and the remaining part isstored in the antenna [2]. Because of this energy stored, widespread to all thefrequencies, such a process generates surface waves (surface currents) on theground plane of the antenna. In the array antenna, the patch antenna operatesas a resonator besides the future radiator. So, the harmonic components mightproduce the problems in this case [3].

Recently, several techniques have been proposed for overcoming the problemof surface waves. One of the effective methods which suits for the millimetrestructures is to use photonic band gap structures. The idea of these struc-tures was proposed by Yablonovich for the first time [4]. Using photonic bandgap structures has become attractive for engineers and researchers workingon antennas, electromagnetic and microwaves. The usages of these materialsare redounded to preventing from the propagation modes of these antennas inthe Forbidden frequency band. Suppressing the surface waves in the desiredfrequencies depends on the PBG structure associated with the antenna substrate.

These structures are used for improving the characteristics of the microstrippatch antennas and resonator antennas. Photonic band gap materials or Elec-tromagnetic Band Gap (EBG) are periodic dielectrics which can suppress thepropagation of the surface waves in certain frequency bands [5]. In [6], typesof substrates with PBG structures probed. Researchers using the PBG in thestructure of the microstrip patch antennas can improve their radiation pattern,decrease side lobe levels and back lobe levels and increase their gain [7]. Also,improvement of the antenna characteristics using PBG was reported in [8].


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Furthermore, in [9], the radiation directivity of the patch antenna was improvedusing PBG cover.

In this paper, a photonic band gap periodic structure is used which is crossshaped in the ground plane of the microstrip patch antenna. The simulatedresults show that characteristics such as the bandwidth, gain and directivity ofthe antenna are improved by adding the PBG structure.

Antenna Design

Figure 1 shows the conventional antenna. To achieve a higher bandwidth, thePBG structures are used in the ground plane. The geometry of the photoniccrystal antenna is shown in Figure 2. The periodic structure is considered byperiodic crosss holes in the ground plane. Figures 2a and b demonstrate thetop and side views. A unit cell of the PBG structure used in the proposedconfiguration is illustrated in Figure 3.

In this paper, the dimension of the patch and the width of the feed line areconsidered 4.3 mm x 4.3 mm and 0.3 mm, respectively. The FR-4 substratesdimension is: 10 mm x 9 mm x 0.32 mm and the relative permittivity is 4.4(Figure 1). All the parameters of the antenna substrate are shown in Table 1.

Figure 1: The Conventional Microstrip Patch Antenna


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Figure 2: (a) Top View and (b) Back View of the PBG Antenna

Figure 3: A Unit Cell of the Periodic Structures

Results and Discussion

The simulated return loss characteristic of the conventional antenna and PBGantenna using HFSS Ansoft are shown in Figures 4 and 5 respectively. Asdiscovered by the figures, the proposed structure improved the bandwidth sothat the bandwidth of the conventional and Proposed antenna is 5.9% and12.6%, respectively. In addition, Figures 6 and 7 illustrate the graph of the gainin both structures.

The preceding simulated results proved that the PBG antenna gain is en-


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Figure 4: Return Loss (S11) of the Conventional Antenna

Table 1: FR-4 Substrate Properties

Properties Value

Permittivity, 4.4

Loss Tangent 0.02

Substrate Length 10 mm

Substrate Width 9 mm

Substrate Height 0.32 mm

hanced in comparison with the patch antenna used alone. The directivityradiation pattern of the conventional antenna and proposed antenna are shownin Figure 8a and 8b separately. As a result for the PBG structure, a 1 dBincrease is achieved in directivity as compared with the non-PBG antennastructure. Besides, the main lobe of the proposed antenna come to be sharperfor = 90o.

Conclusion

Since the surface wave has a robust effect on the conventional microstripantenna structure, the effects of such a phenomenon should be overwhelmed;


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Figure 5: Return Loss (S11) of the PBG Antenna

Figure 6: Gain of the Conventional Antenna

subsequently an increase in the antenna performance would be observable. Inthis paper, a photonic band gap structure was used in the ground plane of themicrostrip antenna. Consequently, the results proved that the surface waveswere suppressed in a certain frequency band, thus the bandwidth, gain and thevalues of the directivity increased from 5.9% to 12.6%, 0.42 dB to 2.47 dB and3 dB to 4 dB, respectively. Hence, the performance of the microstrip antennacan be increased using simple PBG structures.


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HCTL Open Int. J. of Technology Innovations and ResearchHCTL Open IJTIR, Volume 3, May 2013e-ISSN: 2321-1814ISBN (Print): 978-1-62776-443-8 References

Figure 7: Gain of the PBG Antenna

Figure 8: Directivity radiation pattern (a) conventional antenna, (b) proposed antennaat 8 GHz

References

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[2] H. Mosallael, Y. Rahmat-Samii, Photonic-Band Gap (PBG) versus


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[8] X. H. Song, W. Y. Yue, T. G. Shen, Y. Q. Zhou, Investigation ofa patch antenna based on I- shaped left handed material, Optic- Int. J. Light Electron Opt. Vol.122, pp. 1426-1429, (2011).

[9] L. Qing-chun, Z. Fang-ming, H. Sai-ling, A new photonic band gapcover for a patch antenna with a photonic bandgap substrate,J. Zhejiang Univ. SCI, Vol. 5, pp.269-273, (2004)

[10] Mohammad Alibakhshi Kenari, Squeeze Broad-Band PatchAntenna Based on Metamaterial Transmission Line for Portable

Apparatus, HCTL Open International Journal of Technology Innovationsand Research, Volume 2, March 2013, Pages 56-66, ISSN: 2321-1814, ISBN:978-1-62776-111-6.

[11] Mohammad Alibakhshi Kenari, A Novel Compact Ultra Wide BandPlanar Antenna Based on the Composite Right/Left-Handed

Transmission Line Accompanying Improvement Gain, HCTL Open


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International Journal of Technology Innovations and Research, Volume 2,March 2013, Pages 67-77, ISSN: 2321-1814, ISBN: 978-1-62776-111-6.

[12] Mohammad Alibakhshi Kenari, A New UWB Small Dimension MTMAntennas Based on CRLH Transmission Lines for Modern Wireless

Communication Systems and Portable Devices, HCTL Open Interna-tional Journal of Technology Innovations and Research, Volume 2, March2013, Pages 25-55, ISSN: 2321-1814, ISBN: 978-1-62776-111-6.

This article is an open access article distributed under the terms and con-ditions of the Creative Commons Attribution 3.0 Unported License (http://creativecommons.org/licenses/by/3.0/).

c2013 by the Authors. Licensed by HCTL Open, India.


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optimization of microstrip antenna characteristics using photonic band gap structure

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