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Design of Compact Slot Antenna For WLAN Application

S.Sathesh1 C.Rajarajachozhan2
PG Scholar, Department of ECE, Bannari Amman Institute of Technology, Sathyamangalam, Tamilnadu, India1
Assistant Professor, Department of ECE, Bannari Amman Institute of Technology, Sathyamangalam, Tamilnadu, India2
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Abstract

A microstrip fed slot antenna is proposed for wireless local area network (WLAN) operation is designed and simulated using ADS software. Microstrip feed line have been widely used as feeding networks. This paper presents the simulated results of the antenna composed of rectangular patch element embedded with slots, with good imp e d a n c e matching. The overall dimension of the antenna is 25mm × 21mm×4mm . The antenna is characterized by measuring radiation pattern, directivity, return loss and gain. The antenna operates in broad frequency bands from 4 GHz to 6 GHz covering wireless local area network (WLAN) band. The maximum gain of the designed antenna is 6.94dBi at 5.26 GHz frequency band.

Keywords
Coplaner waveguide(CPW)-fed antenna, WLAN, ADS, Radiation Pattern.

INTRODUCTION
The demand for wireless communication is ever increasing all over the world. In recent days microstrip f e d s l o t antennas are v e r y popular for modern wireless communication methods because of their low profile, low manufacturing cost, simple feeding and easy-to-integrate. The capability of the antenna mostly depends upon the parameters. The result can be improved by proper design of antenna elements and choosing appropriate array element configuration. The fast development of wireless techniques, particularly the WLAN application, that includes all the frequency bands of 5.8/5.2/2.4 GHz and , have induced more concentration in the area of research i n antennas with single band or multiple bands. In both military and commercial applications there have been ever growing demands for antennas. A simple arrangement o f a microstrip feeding method has become very famous in WLAN systems . In this article the antenna design with slots has b e e n u s e d to achieve the required WLAN bands. The p r o p o s e d d e s i g n is capable of providing maximum bandwidth to cover WLAN operations at the 5.2 GHz frequency . Various slots are shaped in the radiating patch to manage the current flow on the antenna surface. Slot dimensions are varied to improve the various parameters like gain, return loss.

II. ANTENNA DESIGN AND STRUCTURE
The design of the antenna is shown in figure1. It is designed using the substrate material RT_Duroid 6002 with thickness h= 4mm and dielectric constant ?r = 2.93 and one side has conductor and the other side has no metal contact. The electric field of microstrip lines is mainly normal to the substrate material . A microst rip is used for feeding the antenna which contains the width Wf. E-shaped tuning slot is located at the center of the antenna, where the antenna is symmetrical along the center, x-axis. The final geometric parameters of the designed antenna are given as: length of microstrip Lf = 17.8 mm, width of rectangular patch Wf = 3 mm.

III. RESULTS AND DISCUSSION
The simulation of the design is carried out by the method of moment’s technique (ADS software). The radiation pattern of the microstrip antenna is shown in Fig.2. Fig.3 gives the simulated return loss of the microstrip antenna which is -21.93db at 5.2GHz . The radiated power of the proposed antenna is shown in fig5. The simulated gain and directivity of this microstrip antenna is shown in Fig.6 &Fig.7 which clearly indicates that maximum gain is 6.94dBi. Fig.8 shows effective area of the microstrip antenna. The gain, return loss, directivity, and efficiency of different antenna configurations are shown in table 2. A parametric study is conducted and it c learly shows that the following parameters have made changes on the performance of the designed antenna in terms of bandwidth. The slot length is var ied and the simulat ions were done for the var ious values of slot length.
The Radiation Pattern shows the antenna radiates more power in a certain direction than another direction.
The return loss for the designed microstrip feed slot antenna is -23.9db which is obtained at 5.26GHz. Figure 3 shows that the antenna is tuned at 5.26 GHz frequency. Figure 4 shows smith chart of designed antenna which is a representation of all possible complex impedances with respect to coordinates defined by complex reflection coefficient. The voltage standing wave ratio(VSWR) for the designed antenna is 3 and reflection coefficient is 0.5.
The above graph 5 shows the radiated power of the antenna which is the measure of how much power is radiated by an antenna when the antenna is connected to an actual radio (or transmitter). Here radiated power is obtained as 0.011064 watts.
Antenna gain is defined as the ratio of the power produced by the antenna from a far-field source on the antenna's beam axis to the power produced by a hypothetical lossless isotropic antenna, which is equally sensitive to signals from all directions. Hence we obtain the gain as 6.94dBi which is shown in figure 6.
The directivity of the antenna is the maximum gain of the antenna compared with its gain averaged in all direction. The directivity obtained for the designed antenna is 8.5dBi, Which is shown in Figure 7.
Figure 8 shows the effective area of the antenna which can be defined as functionally equivalent area from which an antenna directed toward the source of the received signal gathers or absorbs the energy of an incident electromagnetic wave. Here we we obtain the effective area as 0.00012 m2.
The linear polarization of the antenna which is the radiates wholly in one plane containing the direction of propagation is shown in figure 9.
The above figure 10 shows the circular polarization of the antenna which can be defined as the polarization in which the electric field of the passing wave does not change strength but only changes direction in a rotary type manner.
The above graph shows the absolute fields of the antenna .Theta is the swept parameter of the planer cut and phi is the swept parameter of the conical cut. E Theta and E phi are the absolute E field strength of theta and phi far field components. H Theta and H phi are the absolute H field strength of theta and phi far field components.

IV. CONCLUSION
An optimal Microstrip feed slot antenna with an extended rectangular shape is designed. The required frequency band for the designed antenna is obtained by using a coplaner waveguide feed structure. S parameter calculation has been performed for the designed antenna.It is clear that the designed antenna has been radiated in the prescribed range of frequency defined for Wireless Local Area Network (WLAN) Applications. The antenna has small size and easy to integrate with in microwave ICs, resulting in reduction of required volume and fabrication cost of the whole system. The simulated result shows a broad impedance bandwidth ranging from 4GHz to 6 GHz, with respect to the tuning frequency at 5.26GHz. Further the antenna parameters such as gain, directivity, effective area, absolute fields, axial ratio, linear polarization and circular polarization of the designed antenna is plotted and analyzed. The stable radiation patterns and good antenna gain over the operating bands has been obtained.

Tables at a glance
Table icon Table icon
Table 1 Table 2
 

Figures at a glance
Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6
Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6


Figure 7 Figure 2 Figure 9 Figure 10 Figure 11
Figure 7 Figure 8 Figure 9 Figure 10 Figure 11
 

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