IJCRR - 4(8), April, 2012
Pages: 119-123
Date of Publication: 25-Apr-2012
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DESIGN OF A COMPACT CPW FED HEXAGON SHAPED SLOT ANTENNA FOR WI-MAX APPLICATION
Author: H. M. Ramesh, K. Balaji, D.Ujwala, B.Harish, Ch. Vijay Sekhar Babu, K.Naga Mallik
Category: General Sciences
Abstract:A compact Coplanar Waveguide (CPW) fed Hexagon shaped slot antenna is proposed for Wi-Max application. The proposed antenna has a size of 20mm x 16.5mm x1.6mm and it is designed on Rogers RT/Duroid substrate with a dielectric constant of 2.2. The proposed antenna resonates at 7.5 GHz and has a bandwidth of 1.2 GHz, Return Loss (S11) of -51.5dB, Gain 3.7 dBi, VSWR of 1 at 7.5 GHz. The near field and far field radiation patterns are bi-directional and Omni-directional in E and H planes. The proposed antenna is used for Wi-Max applications and the antenna has an impedance bandwidth of 86%. The proposed antenna is simulated using Ansoft High Frequency Structure Simulator (HFSS) version 13
which is based on Finite Element Method and the antenna parameters are analyzed.
Keywords: Co-Planar Waveguide (CPW), Near-Field, Far-Field, Wi-Max, Slot antenna.
Full Text:
INTRODUCTION
Worldwide Interoperability for Microwave Access (Wi-Max) [1] with IEEE 802.16 standard is an emerging wireless technology for high data rate transfer of approximately 75Mb/s. The design of wideband antenna with compact size, low profile, light weight and obtaining beneficial results for fundamental antenna parameters like Return Loss, VSWR, Gain and Radiation Patterns is a challenge. A slotted patch antenna fed by a CPW structure provides broad bandwidth with low dispersion and less radiation. Among planar UWB antennas, slot antennas are more preferred because of their higher impedance bandwidth, very good radiation efficiency and less dispersion [2-6]. In this paper, a compact hexagonal shaped slot antenna is proposed which is useful for Wi-Max [7-10] application. The proposed antenna is easy to integrate, low profile with less radiation loss and less dissipation. Since CPW feed implemented here is of ungrounded type, there is no need of ground plate and this improves the radiation characteristics. The proposed antenna is excited with 50 ohms CPW feed.
ANTENNA DESIGN
The geometry of the proposed CPW fed hexagonal slot antenna is as shown in figure 1.
The proposed antenna is designed on Rogers RT/duroid 5880 substrate on one layer metallic side. The relative permittivity of the substrate is 2.2 with a dielectric loss tangent of 0.0009. The overall size of the antenna is 20 x 16.5 x 1.6 mm. The optimum design parameters are shown in figure 1. The feed line width is 2mm at the bottom and increasing towards the top and the width at the top is 3.6 mm. The gap from the coplanar ground plane to the patch is 1.2mm. The length and width of the hexagonal slot is 18 x 10.3 mm. The folded slot dimensions are 6 x 1 mm with a gap of 1 mm between them. The simulation process is carried out using Ansoft High Frequency Structure Simulator (HFSS). The excitation given to this antenna is Lumped port excitation. The Return Loss and Resonant frequency will vary with the dimensions of the patch, coplanar ground plane and substrate.
RESULTS AND DISCUSSIONS
The proposed CPW fed hexagon shaped slot antenna resonates at a single frequency of 7.5 GHz (7 GHz to 8.2 GHz) which has a bandwidth of 1.2GHz. The Frequency vs. Return Loss plot is shown in figure 2 and the return loss at the resonating frequency is -51.5 dB. The VSWR at 7.5 GHz is 1.0 and the plot is shown in figure 3.
The maximum Gain at resonant frequency of 7.5 GHz is 3.73 dBi and the 3D gain plot is shown in figure 4. The Impedance Bandwidth is 86%.
Table 1 represents the output parameters of the antenna like Peak Directivity, Radiated Power, Radiation Efficiency etc. and obtained a Radiation Efficiency of 99.9% which shows that there is less loss of Radiation. Table 2 represents the radiated field data at the resonant frequency 7.5GHz at different Theta and Phi. From the table, Left hand Circular Polarization (LHCP) and Right hand Circular Polarization (RHCP) are approximately equal.
CONCLUSION
A 50 ? CPW fed hexagon shaped folded slot antenna of compact size 20 x 16.5 x 1.6 mm is designed for Wi-Max application with excellent Return Loss of -51.5 dB and desirable peak gain of 3.7 dBi and acceptable VSWR of 1.0 at the resonant frequency 7.5 GHz (7GHz - 8.2GHz). The bandwidth of the designed antenna is 1.2 GHz with an impedance bandwidth of 86%. The E-Plane and H-Plane radiation patterns for different Phi (0 and 90 deg.) and Theta (0 and 90 deg.) values are obtained as quasi Omnidirectional with acceptable Radiation characteristics and desirable Radiation Efficiency.
ACKNOWLEDGEMENT
The authors would like to acknowledge their gratitude towards the management of Department ECE, K. L. University for their support during the work. Authors acknowledge the immense help received from the scholars whose articles are cited and included in references of this manuscript. The authors are also grateful to authors / editors / publishers of all those articles, journals and books from where the literature for this article has been reviewed and discussed.
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