design and analysis of coplanar fed planar ultra-wide band ... · to form a wine glass like...

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Research Paper

International Journal of Informative & Futuristic Research ISSN (Online): 2347-1697

Volume 2 Issue 9 May 2015

Abstract

The rapid investigations and developments taking place in the Ultra-Wide Band (UWB) area has led to the development of a number of antennas working in this band. This paper suggests a new coplanar waveguide fed antenna for ultra-wide band applications. The frequency of operation is from 3.1 GHz to 10.6 GHz. The proposed antenna is based on planar square shape. The edges of the antenna are trimmed off for the purpose of size reduction and ultra-wide band performance. Radiation pattern of the antenna exhibit’s omnidirectional characteristics. This antenna has the advantages of simple structure, reduced size, easiness of fabrication and integration. The antenna was simulated in Ansoft HFSS.

1. Introduction

In the present scenario of increasing number of devices and components used in the ultra-wide band

(UWB) region, a number of antennas working in this band for numerous applications have been

developed. A good antenna system which works efficiently is one of the most valuable assets in the

Design And Analysis Of Coplanar Fed

Planar Ultra-Wide Band Antenna Paper ID IJIFR/ V2/ E9/ 003 Page No. 2980-2987 Subject Area

Elec. & Comm.

Engineering

Key Words Ultra-Wide Band (UWB), Coplanar Waveguide(CPW), Substrate

Sheelu Cyriac 1

M.Tech Student Department of Electronics & Communication Engg. St. Joseph’s College of Engineering and Technology, Palai- Kerala

Tomson Devis 2

Assistant Professor Department of Electronics & Communication Engg. St. Joseph’s College of Engineering and Technology, Palai- Kerala

Litty Baby 3

M.Tech Student Department of Electronics & Communication Engg. St. Joseph’s College of Engineering and Technology, Palai- Kerala

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ISSN (Online): 2347-1697 International Journal of Informative & Futuristic Research (IJIFR)

Volume - 2, Issue - 9, May 2015 21st Edition, Page No: 2980- 2987

Sheelu Cyriac1, Tomson Devis, Litty Baby:: Design And Analysis Of Coplanar Fed Planar Ultra-Wide Band Antenna

ultra-high frequency range. A properly designed, well built and maintained antenna provides with

the advantages of increased transmitting range, enhanced reception of weak signals and reduced

interference issues.

The proposed antenna system is based on planar square antenna. The sides of the antenna

are trimmed off and thus it has got a wine glass like shape. The antenna is of reduced size due to its

planar structure and can be used for short distance communication and cognitive radio applications.

The use of coplanar feeding technique reduces the dispersion, radiation leakage, controls

characteristic impedance and helps to integrate with active devices easily. The antenna takes the

merits of simple structure, size reduction and easiness of fabrication. In addition, by adding

structures such as notches and slits appropriately, the antenna can be further modified according to

applications.

2. Microstrip Patch Antenna

A microstrip patch antenna has two parallel conductors that are separated by a dielectric substrate.

Of the two conductors the lower one acts as the ground and the upper one is the patch. This is the

reason why these types of antennas are called patch antennas. The patch can be of various shapes

such as rectangular, square, elliptical, triangular etc. The advantages of patch antenna are that they

are of light weight and are easy to install. It is because of these properties they are widely used in

aircrafts, missiles and satellite applications. The properties of substrate such as dielectric constant

and thickness are important while considering the design of microstrip patch antennas. Another

important consideration is the method used to feed the antenna.

3. Proposed Antenna

The proposed antenna is based on a planar square structure. The edges of the square are trimmed off

to form a wine glass like structure. This is done to provide the antenna ultra-wideband characteristic

as sharp edges does not support ultra-wide band characteristics. The antenna consists of a single flat

element vertically mounted on a substrate. The ground plane is located on both the lower ends of the

patch. The antenna is fed using coplanar feeding technique.

Figure 3.1 shows the structure of the proposed antenna.

Figure 3.1: Structure of the proposed antenna.

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3.1 Design of the Antenna

As shown in figure 3.1, the wine glass shaped part is the patch, the squares on both sides of the patch

indicate ground and the larger square corresponds to substrate. The detailed design of the antenna is

given below.

Frequency of operation (fo): The resonant frequency of the antenna must be selected

properly. The ultra-wide band frequency range is from 3.1-10.6 GHz. Hence the antenna

designed should be able to operate in this frequency range. The resonant frequency selected

for this design is 5 GHz.

Dielectric constant of the substrate (εr): The dielectric material selected for the design is

FR4, which has a dielectric constant of 4.4. A substrate with a high dielectric constant has

been selected since it reduces the dimensions of the antenna.

Height of dielectric substrate (h): For the antenna to be used in communication

applications, it is necessary that the antenna is not bulky. Hence, the height of the dielectric

substrate is selected to be 1.5 mm. Hence, the essential parameters for the design are:

fo = 5 GHz

fL = 3.1 GHz

fH= 10.6 GHz

εr = 4.4

h= 1.5 mm

Calculation of effective dielectric constant (εeff): εeff = (εr+1)/2 (1)

Calculation of perimeter of the patch (p): fL = c/(√(εeff)p),where c = 3.00e+008 m/s (2)

Calculation of measurements of the feed: The length of the feed should be less than λ/4, where λ is

the wavelength corresponding to the frequency of operation. To avoid microstrip mode, and left and

right grounds are extend away from width of the feed.

The coplanar waveguide (CPW) feeding mechanism has many advantages over microstrip type feed

lines, such as reduced dispersion, reduced radiation leakage, the ability to effectively manage the

characteristic impedance, and its ease of integration with active devices. The antenna fed by a

microstrip line may result in misalignment because of the etching that is required on both sides of

the dielectric substrate. The alignment error can be eliminated if a CPW feed is used to in the slot.

Also fabrication of a coaxial feed is difficult therefore we ended up using a coplanar waveguide as

feed.

Calculation of the measurements of the coplanar waveguide: Width = 3w or 3h; height = 4w or 4h,

whichever is greater, where w = width of the feed and h= height of the substrate.

(3).From the above mentioned equations, the various dimensions used for the design of the antenna

are shown in the figure below:

Figure 3.2: Geometry of the coplanar waveguide.

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Figure 3.3: Geometry of the proposed antenna.

The construction of the antenna begins with the design of the square patch. After designing the

ground and the feed the sides of the square are trimmed off to obtain the ultra-wide band property.

The use of coplanar feeding technology offers a number of advantages for the fabrication of printed-

circuit UWB antennas.

The simulation of the antenna was done in Ansoft HFSS. Figure 3.4 and 3.5 shows the simulated

ultra-wide band antenna.

Figure 3.4: Simulated ultra-wide band antenna.

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Figure 3.5: Simulated ultra-wide band antenna with coplanar waveguide.

4. Results

The design and simulation of the antenna was done in Ansoft HFSS and graphs were

plotted. The plot of reflection coefficient, radiation pattern and 3D polar plot are shown

below.

Figure 4.1: Simulated S11 plot of the antenna

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Figure 4.2: Radiation pattern of the antenna.

Figure 4.3: Plot of VSWR of the antenna

From the graph it can be seen that at 6.77 GHz the value of reflection coeffient, S11 is -21 dB. The

radiation pattern of the antenna has omnidirectional characteristics. The VSWR of the antenna is

1.19 at 6.77 GHz. Thus we can say that the antenna works well in the UWB region.

5. Analysis

To further understand the design of the proposed antenna, some parametric studies are carried out.

The major parameter that affect the frequency and reflection coefficient is height of the grounds.

When height of the ground is increased the distance between the patch and ground is reduced. The

perfomance of the antenna vary considerably in cases of different values. It can be seen from Figure

5.1 that as the height of the ground increases, the perfomance of graph decreases.

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In summary, for a design of a UWB antenna with wine glass shaped structure and a coplanar

waveguide feed the best results are obtained when the distance between ground and patch is

increased. It is analysed that a UWB antenna with reduced size and best perfomance can be obtained

by controlling the height of the ground.

Figure 5.1: Simulated S11 plot of the antenna when height of the ground is increased.

6. Conclusion and Future Scope

From this work, it can be concluded that the ultra-wide band antenna with coplanar feeding

technique gives a viable option for speedy data transfer in short distance communication in the ultra-

wide band region. The radiation pattern of the antenna has omnidirectional characteristics.

Moreover, the antenna has several advantages which includes simple structure, easiness of

fabrication, size reduction and low cost. The proposed ultra-wide band antenna can be further

modified by using slits, slots or notches in appropriate places depending upon the need of the user

and applications. Thus the antenna is flexible and can be used for various applications.

References

[1] Hung-Jui Lam and Jens Bornemann, “Ultra Wideband Printed Circuit Antenna in Coplanar Technology,”

in International Journal of Scientific \& Technology Research, 1-4244-1350-8/07/$25.00 ©2007 IEEE.

[2] H.G SCHANTZ, “Introduction to ultra-wideband antennas,” in IEEE Conf. Ultra Wideband Systems and

Technologies, 1999, pp. 455–457.

[3] ] R.F. Martin, “ Ultra-wideband (UWB) rules and design compliance issues,” in 2003 IEEE EMC-S Int.

EMC Symp. Dig., Vol. 1, pp. 92-96., 2003

[4] J.-Y. Chiou, J.-Y. Sze, and K.-L. Wong, “ A broad-band CPW-fed strip-loaded square slot antenna,” in

IEEE Trans. Antennas Propag., Vol. 51, No. 4, 719-721, 2003.

[5] Constantine A. Balanis, Antenna Theory Analysis and Design(second edition), John Wiley & sons Inc.,

Newyork(1997)

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Biographies

Sheelu Cyriac is an M.Tech Advanced Communication and Information Systems student in

St.Joseph’s College Of Engineering And Technology, Palai. She received B.Tech degree in

Electronics And Communication from Cochin University of Science and Technology.

Tomson Devis is currently working as an Assistant Professor in department of Electronics And

Communication at St.Joseph’s College Of Engineering And Technology, Palai. He pursued the

B.Tech degree in Electronics And Communication from Mahatma Gandhi University and the M.Tech

degree in Microwave and Television Engineering from Kerala University.

Litty Baby is currently doing M.Tech in Advanced Communication and Information Systems at

St.Joseph’s College Of Engineering And Technology, Palai. She pursed the B.Tech degree in

Electronics And Communication from Mahatma Gandhi University.

design and analysis of coplanar fed planar ultra-wide band ... · to form a wine glass like...

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