Enhancement of gain in Microstrip Patch Antenna using EBG structure for WLAN Application

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GRD Journals | Global Research and Development Journal for Engineering | International Conference on Innovations in Engineering and Technology (ICIET) - 2016 | July 2016

e-ISSN: 2455-5703

Enhancement of Gain in Microstrip Patch Antenna Using EBG Structure For WLAN Application 1S.Karpagavalli 2S.R.Shaaru

Nivetha 3D.S.Roland 1,2,3 Department of Electronics and Communication Engineering 1,2,3 Mepco Schlenk Engineering College, Sivakasi, Viruthunagar 626005, India Abstract In this paper, we demonstrate the performance characteristics of the gain, surface waves, return loss of microstrip patch antenna with and without Electromagnetic Band Gap structure (EBG) for WLAN application. Electromagnetic Bandgap Structure (EBG) is mainly focused on overcoming the limitation of Microstrip Patch antenna such as low gain, excitation of surface waves etc., The Microstrip Patch Antenna consists of dielectric substrate with ground plane at one end and patch at other end whereas in EBG concept, additional EBG substrate with EBG cells are inserted in between ground and dielectric substrate. The simulation is done by using High Frequency Structure Simulator (HFSS).We have obtained gain of 14.2 dB for circular EBG and gain of 8.64 dB for rectangular EBG model respectively. Hence, we improved the efficiency of the antenna the EBG model. Keyword- Micro strip Patch Antenna, Electromagnetic Band Gap Structure (EBG), Band Gap Gain, Surface waves, Return Loss __________________________________________________________________________________________________

I. INTRODUCTION Wired LAN is replaced by Wireless LAN (WLAN) and is considered as an adjunct of wired LAN infrastructure which uses microwave band. In general there are two antennas in WLAN application which is mobile communication terminal and other is fixed WLAN base station. For base station application return loss needs to be greater than 14 dB (6). WLAN system requires low profile antenna in order to reduce the overall size of WLAN system. IEEE 802.11b is most commonly used WLAN system. These requirements were satisfied by microstrip patch antenna. With a rapid development in wireless field, microstrip patch antenna plays a major role in antenna community. Advantages of patch antenna were low profile, low fabrication cost etc. Excitation of surface waves is the major drawback of this type of antenna. In ordinary microstrip patch antenna, ground plane redirects one half of the radiation in opposite direction which affects the antenna gain. For complete radiation we need Îť/4 spacing in between ground plane and antenna. It is illustrated in Fig. 1.

Fig. 1: Illustration of difference in spacing between ground plane and antenna with and without EBG.

Since there is radiation in backward direction in basic micro strip patch antenna (MSA) due to back lobes we need to have infinitely large ground plane to avoid radiation in backward direction. But practically infinite ground plane is not feasible. Excitation of surface waves in the substrate layer is main factor which reduce gain and efficiency. Surface waves occur when patch radiates, it only redirects the portion of total absorbed power. Therefore some of the power is trapped within the substrate layer. Surface waves can be suppressed by using concept called Electromagnetic Band Gap Structure (EBG).

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