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Designing of pattern reconfigurable antenna for wireless applications.

INTRODUCTION

With the rapid development of wireless communication systems, reconfigurable antenna has received much attention, since it can change the radiation pattern, frequency and polarization to improve the overall system performance [1]. Most reconfigurable systems concentrate on changing operating frequency while maintaining radiation characteristics. However, changing radiation patterns while maintaining operating frequency and bandwidth could greatly enhance system performance [2]. Manipulation of an antenna's radiation pattern can be used to avoid noise source, improve security and save energy by better directing signal toward intended direction [1,3]. Therefore there is a great demand for pattern reconfigurable antennas in the fields of wireless communications.

Usually, the pattern reconfiguration feature is attained by phased antenna arrays, which may be too large, too complex and too costly to satisfy the requirements of many applications. The pattern reconfigurable antennas without phased arrays have attracted a lot of interest in some applications recently. Because of some advantages of symmetrical structure, the pattern reconfigurable antenna with symmetry feature has been studied a lot, such as a beam reconfigurable antenna based on a symmetrical folded dipole structure, a wideband pattern reconfigurable antenna with symmetrical switchable feed structure [4], a reconfigurable patch antenna with symmetrical slotted parasite radiator [5], a reconfigurable microstrip antenna with symmetrical slotted parasite array, a reconfigurable rectangular patch antenna with symmetrical parasite folded dipole, etc.

Most reconfigurable antennas have studied only one reconfigurable characteristic (pattern, frequency or polarization). While the antenna, which can achieve two or more reconfigurable characteristics could enhance system performance greatly.

This proposed work introduces a circular disc-shaped reconfigurable antenna capable of pattern reconfigurability. Using the set of switches to change the connection between the central patch and four surrounding parasitic patches, the pattern reconfigurable characteristic can be achieved.

II. Antenna structure:

A. Substrate selection:

The first step in the design is to choose a suitable dielectric substrate of appropriate thickness (h) and loss tangent. A thicker substrate, besides being mechanically strong it will increase the radiated power, reduce the conductor loss and improve impedance bandwidth. Here FR 4 Substrate is used. Because, the dielectric constant of FR4 substrate is [[epsilon].sub.r] = 4.4 and loss tangent value, tan [delta] = 0.02, by increasing the height of the substrate automatically increases the efficiency. Here the height of the substrate is 1.6 mm. The bandwidth of the patch antenna is increased by use of high dielectric constant of substrate.

B. FR-4 Substrate:

FR-4 substrate is a very common and by far the most used substrate in consumer electronics market as it has a good quality-to-price ratio. It is mostly used where cost is more efficient. FR-4 is a standard with many different distributors making many different FR-4 quality and property boards. It is made of woven fibreglass with an epoxy resin binder (binds the copper clad to the dielectric substrate) that is flame resistant. The dielectric constant goes down the more the FR-4 PCB is reinforced with epoxy resin instead of fibreglass as this is not determined as a standardized parameter.

B. Disc Shaped Patch Antenna:

The basic structure of the proposed Disc shaped patch antenna is shown in Fig. 1. The circular microstrip antenna is chosen because it provides 360[degrees] beam coverage when compare to rectangular microstrip patch antenna. In rectangular micro strip patch antenna, the dimensions of the patch are finite along the length and width, the fields at the edges of the patch undergo fringing. But in circular microstrip antenna, there is no sharp edge so fringing effect is reduced.

The antenna consists of a central circular patch and four surrounding fan ring parasitic patches. The proposed circular patch antenna is made up of copper microstrip material. By reconfiguring the current flow path on each patch, the different types of radiation pattern is achieved. By controlling the states of one set of connections between the central patch and parasitic patches, it is carried out. Here, for proof of concept use thin copper strip as a switch material.

D. Coaxial Feed Technique:

In this proposed antenna use coaxial probe feed technique. Because, it provides better impedance matching (50 [OMEGA]) on driven terminal type in HFSS. The coaxial probe feed is also easy to fabricate and match. It also has low spurious radiation. The coaxial probe feed on patch matching 50 [OMEGA] is given by following equation:

[Z.sub.o] = 138 [OMEGA] [log.sub.10] (D / d) Where, D = Outer diameter of coax d = Inner diameter of core

III. Simulation results:

An soft HFSS employs the Finite Element Method (FEM). In this proposed work Ansoft HFSS can be used to calculate parameters such as S Parameters, Resonant Frequency, and Fields.

A. Single pin configuration:

By using single thin copper strip between the center of patch and any one of the surrounding parasitic patches and connecting between them provides unidirectional pattern. It also meet nearly 50 [OMEGA] impedance matching by using coaxial probe feed technique.

The antenna operates at the resonant frequency of 4.5 GHz. The achieved Return loss of proposed antenna is nearly--40 dB at 4.5 GHz.

The achieved VSWR is 1.5 at resonant frequency.

The proposed antenna is viewed in Azimuthal plane having [phi] = constant plane that contains the pattern's maximum. It is the principle of H-plane.

B. Dual pin configuration:

By using two thin copper strips between the center of patch and any two of the surrounding parasitic patches. The two selected patches allow the electric field distribution along its direction and provides bidirectional pattern. It also meet nearly 50 [OMEGA] impedance matching by using coaxial probe feed technique.

Maximum return loss is achieved at my designed antenna frequency i.e., 4.5 GHz. The achieved Return Loss of proposed antenna for this configuration is nearly--25 dB at 4.5 GHz.

The achieved VSWR of proposed antenna for this configuration is 1.12 at 4.5 GHz.

The proposed antenna is viewed in Azimuthal plane having [phi] = constant plane that contains the pattern'smaximum. For 2 pin configuration, it provides bidirectional pattern.

Conclusion:

Reconfigurability has become an important and desired feature of modern, agile, radio-frequency (RF) systems for wireless and satellite communications, sensing, and imaging. In this work represents antenna for wireless communication, particularly Wi-Fi and also for C band application. The proposed antenna topology is based on the pattern reconfigurable antenna. The antenna is designed using FR-4 dielectric substrate and feeding method is given by coaxial probe feed technique. The antenna can be easily designed to operate effectively at 4.5 GHz. By this disc shaped antenna, different patterns such as unidirectional, bidirectional and omni directional pattern are achieved. It also provides good return loss above -20 dB, peak gain as 13 dBi and better efficiency. The advantage of this antenna is compact and achieves multi patterns at the same resonant frequency. The model is designed and simulated by Ansoft HFSS. In future this proposed work can be modified for frequency and polarization Reconfigurability for wireless applications.

REFERENCES

[1.] Kang, W.S., J.A. Park, Y.J. Yoon, 2008. "Simple reconfigurable antenna with radiation pattern," Electronics Letters, IEEE, 44: 128.

[2.] Symeon Nikolaou, Ramanan Bairava subramanian, Cesar Lugo, Jr., Ileana Carrasquillo, Dane C. Thompson, George E. Ponchak, John Papapolymerou and Manos M. Tentzeris, 2006. "Pattern and Frequency Reconfigurable Annular Slot Antenna Using PIN Diodes", IEEE Transactions on Antennas and Propagation, 54(2): 439-448.

[3.] Xuesong Yang, Bingzhong Wang, Weixia Wu, Shaoqiu Xiao, 2007. "YagiPatch Antenna with Dual-Band and Pattern Reconfigurable Characteristics, "Antennas and Wireless Propagation Letters, IEEE, 6: 168.

[4.] Lee, H.M., 2010. "Pattern Reconfigurable Micro-strip Patch Array Antenna using Switchable Feed-Network" Proceedings of Asia-Pacific Microwave Conference, FR1G-12, pp: 2017-2020.

[5.] Matthias John, S.V. Shynu and Max J. Ammann, 2010. "A Pattern Reconfigurable Slot Antenna with Hybrid Feed ", European Conference on Antennas and Propagation--EuCAP, Barcelona, Spain, We-35.

[6.] Pei-Yuan Qin, Y. Jay Guo, Andrew R. Weilyand Chang-Hong Liang, 2012. "A Pattern Reconfigurable U-Slot Antenna and Its Applications in MIMO Systems", IEEE transactions on antennas and propagation, 60(2): 516-528.

[7.] Shing-Lung Steven Yang, and Kwai-Man Luk, 2006. "Design of a Wide-Band L -Probe Patch Antenna for Pattern Reconfiguration or Diversity Applications", IEEE Transactions on Antennas and Propagation, 54(2): 433-438.

(1) Elamaran. P and (2) Srivatsun. G

(1) Department of electronics and communication, University college of Engineering, Pattukkottai, India.

(2) Department of electronics and communication, P.S.G College of Technology, Coimbatore, India.

Received 28 February 2017; Accepted 22 May 2017; Available online 6 June 2017

Address For Correspondence:

Elamaran. P, Department of electronics and communication, University college of Engineering, Pattukkottai, India. E-mail: ela.india1@gmail.com

Caption: Fig. 1: The geometry of the proposed antenna

Caption: Fig. 2: HFSS model of single pin configuration

Caption: Fig. 3: Return Loss of single pin configuration

Caption: Fig. 4: VSWR of single pin configuration

Caption: Fig. 5: Unidirectional Pattern

Caption: Fig. 6: HFSS model of double pin configuration

Caption: Fig. 7: Return Loss of single pin configuration

Caption: Fig. 8: VSWR of single pin configuration

Caption: Fig. 9: Bidirectional Pattern
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Author:Elamaran, P.; Srivatsun, G.
Publication:Advances in Natural and Applied Sciences
Article Type:Report
Date:Jun 1, 2017
Words:1497
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