PERFORMANCE ANALYSIS OFCURVED U-SLOT PATCH ANTENNA WITH ENHANCED BANDWIDTH AND ISOLATION FOR MIMO...

International Journal of Exploring Emerging Trends in Engineering (IJEETE)

Vol. 02, Issue 01, JAN, 2015 WWW.IJEETE.COM

ISSN 2394-0573 All Rights Reserved 2014 IJEETE Page 11

PERFORMANCE ANALYSIS OFCURVED U-SLOT PATCH ANTENNA WITH

ENHANCED BANDWIDTH AND ISOLATION FOR MIMO SYSTEMS

A. K. SHUKLA1 B.V.V. RAVINDRA BABU

2 UMESH KUMAR

3

1 Assistant Professor and Head, Dept of EC and IC, College of Science & Engineering ,Jhansi, (U.P.)

2 Assistant Professor, Dept of EC, Aditya College of Engineering, Madanapalle (AP)

3

PG Student, Dept of EC, College of Science & Engineering, Jhansi, (U.P.)

ABSTRACT: The paper presents a compact tri band

Curved U-Slot patch antenna with improved bandwidth and

isolation characteristics. The proposed antenna excited by

coaxial feed resonates at tri band of 2.8 GHz, 4.1 GHz and

5.7 GHz for VSWR 1.5 with an improved bandwidth of 99.7% and also for getting high gain antenna of 11.31 dB. A

22 MIMO is developed using the proposed antenna giving

an excellent isolation of 28 dB between the two antennas.

The simulation results of return loss, Mutual Coupling,

Gain, VSWR, Surface Current Distribution and Electrical

Distribution are presented. By keeping the substrate

thickness constant over various dielectric constants,

simulations were carried out using MATLAB and HFSS

(High Frequency Structure Simulator) software.

Keywords: Curved U-slot patch antenna, Impedance

bandwidth, Mutual coupling and Dielectric constant.

INTRODUCTION

Microstrip or patch antennas are most preferred

antennas because they can be printed directly onto a circuit

board. Microstrip antennas are becoming very popular

within the mobile phone market. Patch antennas are low

cost, have a low profile and are easily fabricated.

The major disadvantage of microstrip antennas is

their low bandwidth. The U shaped patch antennas gained

popularity due to their wideband nature. In 1995 a broad

band single layer probe fed patch antenna with a u-shaped

slot was presented by Huynh and Lee [1] and [5]. However,

the general microstrip antennas suffer from narrow

bandwidth, which limits their application in modern

communication systems like MIMO systems etc. Recently,

tri-band antennas gained attention as they can be used for

various applications including Wi Max [6].

MIMO technology gained popularity in wireless

communications as they offer significant data throughput

and link range without additional bandwidth or increased

transmit power. Also they achieve array gain that improves

the spectral efficiency and diversity gain that improves the

link reliability with reduced fading .Because of these

properties, MIMO is an important part of modern wireless

communication standards such as IEEE 803.11 in (Wi-Fi),

4G, 3GPP Long Term Evolution, Wi-MAX and HSPA+.

The main parameter regarding MIMO systems is

mutual coupling, which depends on the distance between the

elements in a MIMO system. If the distance is more, the

mutual coupling between antennas becomes less and vice

versa. Hence, by increasing the distance between the

elements we can reduce the mutual coupling between the

antennas. However, the distance between the antennas

cannot be maintained too large, since MIMO systems have

their major applications in Mobile terminals, laptops, and

WLAN Access Points Wireless communications [4], where

size of the device cant be maintained too large. The main

source of mutual coupling is surface current flowing through

ground in order to reduce these, there are several techniques

like Electromagnetic band gap structure, defected ground

structure [8,9], decoupling techniques, etc However, all

these methods make the design of the antenna entangled.

In the present work, a Curved U-Slot patch antenna

MIMO system is proposed with improved bandwidth and

reduced mutual coupling. The desired antenna resonates at a

tri-band of 2.8 GHz, 4.1 GHz, and 5.7 GHz frequencies with

an improved impedance bandwidth of 99.7% (2.3 GHz-7

GHz) and the obtained mutual coupling between the antenna

elements is small and is less than -28 db.In section 2, the

proposed antenna geometry is presented and in Section 3 the

two element MIMO array system is presented.

ANTENNA DESIGN

The main objective of the antennas used in MIMO

systems is to improve the bandwidth of the patch antenna.

The dielectric constant of the substrate decides the

bandwidth of the microstrip antennas. Low dielectric

constant of the substrate produces larger bandwidth, while

high dielectric constant of the substrate results in smaller

size and low bandwidth [7]. The bandwidth of microstrip

antennas can be increased by several techniques such as

keeping parasitic elements on the patches, increasing the

substrate thickness, inserting slots and using defected

ground structures [9].The patch antennas are fabricated with

various shapes and most of them are widely designed

antennas are E shaped patch antenna, H shaped patch

antenna [10] etc. Among all these antennas, E shaped patch




antennas are widely used as they give better performance in

terms of both impedance bandwidth and mutual coupling.

The U-Slot patch antenna can be formed by cutting three

rectangular slots on a rectangular patch and also using

polyline to cut frontends and edges of the rectangular slots

as shown in Figure 1.The dimensions of the geometry are

given in the Table 1. For better performance, a thick

dielectric substrate having a low dielectric constant is

desirable as it provides better efficiency, larger bandwidth

and better radiation. Here, the substrate selected for the

design of the proposed antenna is RT/duroid5880 of

thickness 6.4 mm and with low permittivity (r=2.2). The

dimensions of the substrate are taken as 60 40 6.4 mm3.

Figure 1: The top and side views of the proposed Curved

U-Slot patch antenna

Table 1: The dimensions of the patch and substrate are

in millimeters

The proposed antenna resonates at tri-band of 2.8

GHz, 4.1 GHz and 5.7 GHz frequencies for VSWR 1.5

with an improved impedance bandwidth of 99.7% and a

reduced mutual coupling of -28 dB. The antenna has been

simulated by using HFSS software.

RESULTS AND ANALYSIS

The proposed antenna is simulated using

MATLAB and HFSS (High Frequency Structure

Simulator) software. The analysis on results obtained for

different parameters of proposed antenna is as follows:

RETURN LOSS

Return loss indicates the amount of delivered

power loss due to reflections.It is the ratio of power

reflected to the power delivered expressed in negative

logarithmic dB. The more return loss tends to negative

value,the effective is the power delivery.The proposed

antenna is operated at the frequency of 3 GHz and it

resonates at 2.8 GHz with wide band characteristics. The

range of frequencies between 2.3 GHz-7 GHz is covered

within a single broad band. The return loss, S11= -25dB can

be measured from the plot at the centre frequency of 5.7

GHz.The impedance bandwidth measured from the plot is

99.7% which ismore than the maximum available

bandwidth. The return loss plot of the designed antenna is

shown in the figure 2.

Figure 2:The return loss of the proposed antenna.

Here, the substrate selected for the design of the

proposed antenna is verified by using different materials

such asRT/duroid5880, Epoxy, FR4_epoxy and Rogers

RO60006 among all these parameters RT/duroid5880

substrate produces high impedance bandwidth as shown in

Table 2 and the return loss plot is sown in Figure3.

Table 2:Different bandwidths obtained for different

materials.

S.NO

.

Material

Dielectric

constant

Impedance

Band Width

1) Rogers

RT/Duroid5880

2.2 99.6%

2) Epoxy 3.6 59.8%

3) FR4 epoxy 4.4 55.6%

4) Rogers RO6006 6.15 26%

As the dielectric constant of the material increases

then the bandwidth will decrease we can observe in the




Table 2. Figure 3 shows the return loss plot of different

materials with a dielectric constant ranges from 2.2 to 6.2.

Figure 3:The return loss plot of Different bandwidths

obtained for different materials.

RADIATION PATTERN

Radiation pattern is a graphical representation of the antenna

radiation properties as a function of spherical coordinates in

desired direction The radiation or antenna pattern describes

the relative strength of the radiated field in various

directions from the antenna, at a constant distance. The

radiation pattern is a reception pattern as well, since it also

describes the receiving properties of the antenna. The

radiation characteristics of the designed antenna is

represented by the 2D radiation pattern at Phi=0 deg, Phi=90

deg for all theta as observed from the fig-8.The patch's

radiation at the fringing fields results in a certain far field

radiation pattern. This radiation pattern shows that the

antenna radiates more power in a certain direction than

another direction.

(a) 2.8 GHz (b) 4.1 GHz

(c) 5.7 GHz

Figure 8: Radiation patterns of the proposed antenna

The variations of power radiated by the proposed antenna at

triple band are shown here.

Figure 9: 3D polar plot of the proposed antenna

EXPORT PARAMETERS

Peak Directivity 2.15902

Radiated Power 0.0116695(W)

Accepted Power 0.0117432(W)

Incident Power 0.0120757(W)

Radiation Efficiency 0.99373

CONCLUSION

In this paper, a novel compact tri band Curved U-

Slot patch antenna is proposed and a two element MIMO

array is developed using the proposed antenna has a

compact size of 60mmx40mm.The proposed antenna excited

by coaxial feed resonates at tri band of 2.8 GHz, 4.1 GHz

and 5.7 GHz for VSWR 1.5 with an improved bandwidth

of 99.7% and also for getting high gain antenna of 11.31 dB

was obtained using RT/duroid5880 substrate material

which a dielectric constant of 2.2. A 22 MIMO is

developed using the proposed antenna giving an excellent

isolation of 28 dB between the two antennas. In this paper,

design of for small-size wide-bandwidth patch antennas has

been presented. These designs combine the wideband U-slot




and different substrate material. The results prove that using

a substrate material with a lower dielectric constant

substrate constant in design of MPA leads to better

performance. The proposed antenna is expected to have

numerous applications in the modern communication

systems such as 4G, WLAN,Wi-MAX, UMTS and Ultra

Wide Band applications. The proposed study can be

extended by employing more number of antennas in MIMO

system for improving the channel capacity of the MIMO

systems in future.

REFERENCES

[1] K. F. Lee, K. M. Luk, K. F. Tong, S. M. Shum, T.

Huynh and R. Q. Lee, Experimental and simulation studies

of the coaxially fed U-slot rectangular patch antenna, Inst.

Elect. Eng. Proc. -Microw. Antennas Propagat., vol. 144,

(1997) October, pp. 354-358.

[2] ShahramMohanna, Ali Farahbakhsh, and SaeedTavakoli

Mutual Coupling Reduction in Two-Dimensional Array of

Microstrip Antennas Using Concave Rectangular Patches

International Journal of Telecommunications, Volume 2,

Issue 2, May 2010.

[3] K. L. Wong, Compact and Broadband Microstrip

Antennas. New York: Wiley, 2002.

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Communications Vol.4, Issue 5 (2013), pp.1-14

[6] T. Huynh and K. F. Lee, Single-layer single-patch

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16, (1995), pp. 13101312.

[7] K. J. Babu, K. S. R. Krishna and L. P. Reddy, A triband

swastika shaped patch antenna with reduced mutual

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[8] D. M. Pozar, Microstrip Antennas, Proc. IEEE, vol.

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[10] K. J. Babu, K. S. R. Krishna and L. P. Reddy, A Multi

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(2001), pp. 165-187.

[12] A. K. Shackelford, K. -F. Lee and K. M. Luk, Design

of Small-Size Wide-Bandwidth Microstrip-Patch Antennas,

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1, (2003) February.

[13] L. H. Weng, Y. C. Guo, X. W. Shi and X. Q. Chen,

AN OVERVIEW ON DEFECTED GROUND

STRUCTURE, Progress In Electromagnetics Research B,

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[14] K. Siakavara, Methods to Design Microstrip Antennas

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[15] K. JagadeeshBabu, Dr.K.Sri Rama Krishna,

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AUTHORS BIBLOGRAPHY

UMESH KUMAR Received

B.E in Electronics &

Communication Engineering

from ANNA University,

Tamilnadu, INDIA. Presently he

is pursuing M.Tech in

Electronics & Communication

Engineering from UPTU Lucknow (UP) INDIA.

He attended so many National Conferences,

Workshops and Published Many Papers in

National and International Journals.

A K. SHUKLA Received

B.Tech and M.Tech in

Electronics & Communication

Engineering from U.P.T.U.

LUCKNOW INDIA. Presently

Working as Asst. Professor and

HOD of EC & IC Departments in SRGI JHANSI

(UP). He attended so many National Conferences,

Workshops and Published Many Papers in

National and International Journals




B.V.V RAVINDRABABU Received B.Tech in Electronics &

Communication Engineering from

M.I.S.T- SATTUPALLI (JNTU)

and M.Tech in VLSI DESIGN from

Sathyabama University,

Chennai .Presently working as

Asst. Professor (ECE Department) in Aditya

College of Engineering, Madanapalle (AP). He

attended many National Conferences, Workshops

and Published Many Papers in National and

International Journals.

PERFORMANCE ANALYSIS OFCURVED U-SLOT PATCH ANTENNA WITH ENHANCED BANDWIDTH AND ISOLATION FOR MIMO...

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