International Journal of Electronics and Communication … CIRCULARLY... · 2014. 3. 5. · This paper presents a circularly polarized microstrip square patch antenna with single

International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN

0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME

324

DESIGN OF CIRCULARLY POLARIZED MICROSTRIP SQUARE-

PATCH ANTENNA FOR IMPROVED BANDWIDTH AND

DIRECTIVE GAIN WITH LOW RETURN LOSS

Sandeep Kumar1, Suresh Sahni

2, Ugra Mohan Kumar

3, Devendra Singh

4

1(Assistant Professor, Uttaranchal University, Dehradun, India,)

2(M.Tech Scholar, Uttarakhand Technical University, Dehradun,)

3(M.Tech Scholar, Uttarakhand Technical University, Dehradun,)

4(Assistant Professor, Uttaranchal University, Dehradun,)

ABSTRACT

This paper presents a circularly polarized microstrip square patch antenna with single

feed technique that operates in wireless local area network. Compact circularly polarized

(CP) microstrip antenna with inserted thin slots is proposed to reduce the size and widen the

bandwidth. The antenna is operated at 3.55 GHz frequency. The impedance bandwidth

(VSWR < 2) is 180 MHz and the directive gain is 5.81 dB. The proposed antenna also

provides low return loss (S11=-31.53dB). The proposed structure is designed and simulated

by Ansoft HFSS software. The simulated results give significant improvement in terms of

directive gain and bandwidth.

Keywords: Bandwidth, Directive Gain, VSWR, Radiation pattern, Return loss.

I. INTRODUCTION

Designing a circularly polarized microstrip antenna is challenging; it requires

combination of design steps. The first step involves designing an antenna to operate at a

given frequency. In the second step circular polarization is achieved by either introducing a

perturbation segment to a basic single fed microstrip antenna, or by feeding the antenna with

dual feeds equal in magnitude but having 90° physical phase shift[6,7]. The shape and the

dimensions of the perturbation have to be optimized to ensure that the antenna achieves an

axial ratio that is below 3 dB at the desired design frequency.

INTERNATIONAL JOURNAL OF ELECTRONICS AND

COMMUNICATION ENGINEERING & TECHNOLOGY (IJECET)

ISSN 0976 – 6464(Print)

ISSN 0976 – 6472(Online)

Volume 4, Issue 2, March – April, 2013, pp. 324-331 © IAEME: www.iaeme.com/ijecet.asp

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Now a day’s circular polarization is very important in the antenna design industry, it

eliminates the importance of antenna orientation in the plane perpendicular to the propagation

direction, it gives much more flexibility to the angle between transmitting & receiving

antennas, also it enhances weather penetration and mobility. It is used in a bunch of

commercial and militarily applications [3, 6]. However it is difficult to build good circularly

polarized antenna.

In a typical wireless communication system increasing the gain of antennas used for

transmission increases the wireless coverage range, decreases errors, increases achievable bit

rates and decreases the battery consumption of wireless communication devices. One of the

main factors in increasing this gain is matching the polarization of the transmitting and

receiving antenna [1, 3].

The microstrip antenna is one of the most commonly used antennas in applications

that require circular polarization. This paper is concerned with the design of a circularly

polarized microstrip antenna that would operate in the 3.6 GHz range. This range is

commonly used by wireless local area devices and wireless personal area devices such as the

802.11 WIFI and the 802.15.4 Zigbee wireless systems [2, 5].

For circular polarization to be generated in microstrip antenna two modes equal in magnitude

and 90 out of phase are required. Microstrip antenna on its own doesn’t generate circular

polarization; subsequently some changes should be done to the patch antenna to be able to

generate the circular polarization

2. FEED TECHNIQUES

The most commonly used feeding techniques in circular polarization generation are

dual feed and single feed [5, 6, and 7].

2.1 Dual Feed Circularly Polarized Microstrip Antenna

As 90° phase shift between the fields in the microstrip antenna is a perquisite for

having circular polarization, dual feed is an easy way to generate circular polarization in

microstrip antenna. The two feed points are chosen perpendicular to each other as shown in

Figure1. With the help of external polarizer the microstrip patch antenna is fed by equal in

magnitude and orthogonal feed. Dual feed can be carried out using quadrature hybrid, ring

hybrid, Wilkinson power divider, T-junction power splitter or two coaxial feeds with physical

phase shift 90°.

Fig.(1) Examples for dual fed CP patches [1, 2, 3]


0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March

2.2 Single feed circularly polarized microstrip antenna

Single fed microstrip antennas are simple, easy to manufacture, low cost and compact

in structure as shown in Figure(2

very complicated to be used in antenna a

antennas are considered to be one of the simplest antennas that can p

polarization[2, 6].

In order to achieve circular polarization using only single feed two degenerate modes

should be exited with equal amplitude and 90° difference. Since basic shapes microstrip

antenna produce linear polarization there must be some changes in the patch design to

produce circular polarization. Perturbation segments are used to split the field into two

orthogonal modes with equal magnitude and 90° phase shift. Therefore the circular

polarization requirements are met

Fig.

3. DESIGN OF MICROSTRIP

POLARIZATION

Design of microstrip patch antenna depends mainly upon three parameters, namely substrate

and its dielectric constant, height of the substrate and resonant frequency. In this paper,

selected three parameters are: Resonant Frequency (f

2.2, Height of the dielectric substrate (h)

Microstrip Patch antenna with square patch

Fig. (3) Microstrip square patch antenna


6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME

326

larly polarized microstrip antenna


2). It eliminates the use of complex hybrid polarizer, which is

very complicated to be used in antenna array [17]. Single fed circularly polarized microstrip

antennas are considered to be one of the simplest antennas that can produce circular


exited with equal amplitude and 90° difference. Since basic shapes microstrip



thogonal modes with equal magnitude and 90° phase shift. Therefore the circular

polarization requirements are met[3, 6].

Fig. (2) Single fed patches [1, 2]

MICROSTRIP SQUARE PATCH ANTENNA WITH

antenna depends mainly upon three parameters, namely substrate


selected three parameters are: Resonant Frequency (fr) = 3.55 GHz, Dielectric constant (

2.2, Height of the dielectric substrate (h) = 1.57 mm. Fig.(3) represents the designed

with square patch. Designed antenna has linear polarization.

Microstrip square patch antenna Fig. (4) Circularly polarized microstrip antenna


April (2013), © IAEME


. It eliminates the use of complex hybrid polarizer, which is

]. Single fed circularly polarized microstrip

roduce circular


exited with equal amplitude and 90° difference. Since basic shapes microstrip



thogonal modes with equal magnitude and 90° phase shift. Therefore the circular

LINEAR

antenna depends mainly upon three parameters, namely substrate


GHz, Dielectric constant (εr) =

represents the designed

Designed antenna has linear polarization.

microstrip antenna



327

3.1 Calculation of Width The width of the Microstrip patch antenna is given by equation (1) [1, 2]:

1

2

2 +=

rf

cW

ε (1)

The calculated width of proposed square patch antenna from equation (1) is W= 32.94 mm,

where c is the speed of light.

3.2 Calculation of Effective dielectric constant (εeff): 2/1

1012

1

2

1

+

−+

+=

W

hrr

reff

εεε (2)

The calculated effective dielectric constant from equation (2) [1], ε reff = 2.329.

3.3 Calculation of the Effective length (Leff):

eff

efff

cL

ε2= (3)

From above equation the effective length is comes out to be [1, 3], Leff=27.30mm

3.4 Calculation of the Length Extension (∆L):

)8.0/).(258.0(

)264.0/).(3.0(412.0

+−

++=∆

hW

hWhL

eff

eff

ε

ε (4)

Which comes out to be [1, 2] ∆L =0.8008mm.

3.5 Calculation of the resonant length of patch (L):

L = LEFF – 2 ∆L (5)

This comes out to be 25.698mm.

3.6 Calculation of radiation conductance (G):

The radiation conductance for a parallel-plate radiator as [1, 2]

−=

24

)(1

2

0

khWG

ηλ

π= 3.2944mS. (6)

3.7 Calculation of input resistance of the patch (R):

GR

2

1= =151.768Ohms (7)

4. DESIGN OF SINGLE FED CIRCULARLY POLARIZED MICROSTRIP SQUARE PATCH

ANTENNA

Single feeding techniques are very common with microstrip antennas as they are

simple, easy to manufacture, low in cost and compact in structure. Several techniques were

used to achieve circular polarization in single fed microstrip antenna. Among these

techniques: fractal boundary, square patch with shaped slots , embedding cross slot in



328

metallic patch or the ground plane, staking antennas, annular ring with strip line inside the

inner ring , and truncated edges patches.

In this paper proposed technique is square patch with shaped slot utilized. this is the

type of single fed circularly polarized microstrip antenna. Now, for achieving circular

polarization cut a thin slot in square patch with dimensions given below and the structure is

shown in above Fig.4.

C=L/2.72 [1]=W/2.72=25.702/2.72

=9.449mm

D=C/10 [1]=L/27.2=W/27.2=25.702/27.2

=0.9449mm

5. ANALYSIS AND RESULTS:

Starting with the values we get from theoretical design, we prepared a model of

antenna in Ansoft HFSS. Since the theoretical design is based on closed loop formulas and

the software is based on open loop formulas, the resonant frequency of the patch designed

with theoretical values shifted to a lower frequency.

Therefore to correct the value of frequency to 3.55GHz, we changed the dimensions

of the patch and the quarter wave transformer. We iteratively simulate the design to get the

resonant dimensions of the patch. The results of the circularly polarized square patch antenna

are given below in Table (1):

Table (1): Results of circularly polarized microstrip antenna

Parameters Practical design

Frequency f 3.55Ghz

Return Loss -31.53dB

VSWR 1.05

Gain 5.721dB

Directivity 5.81dB

Bandwidth VSWR < 2 180Mhz

5.1 Simulated Results of a Circularly Polarized Microstrip Antenna The proposed antenna has been designed and simulated using Ansoft HFSS software.

Fig. (5) represents the variation of Return Loss with Frequency. Plot shows resonant

frequency at 3.55 GHz with minimum -31.53 dB returns loss available at resonant

frequency.

The bandwidth of the antenna depends on the patch shape, resonant frequency,

dielectric constant and the thickness of the substrate [4, 7]. The bandwidth enhancement of a

microstrip antenna has been directed towards improving the impedance bandwidth of the

antenna element. Impedance bandwidth is usually specified in terms of a return loss. The

VSWR of microstrip square patch antenna is shown in Fig. (6).



Fig. (5)

Fig. (6)

Fig. (7) Radiation pattern of



329

Fig. (5) Return Loss vs. Frequency

Fig. (6) VSWR vs. frequency

Radiation pattern of circularly polarized microstrip antenna



circularly polarized microstrip antenna



Fig. (8) Directivity of

6. CONCLUSION

A square patch circularly polarized microstrip antenna design has been proposed and

successfully implemented. The

HFSS software. The square patch circularly polarized antenna

bandwidth, directive gain and return loss (S11 parameters) of

with broad side radiation pattern. The circularly polarized microstrip antenna can be used for

wireless local area network (WLAN, IEEE 802.11), as

REFERENCES:

[1]ong Hee Park,Design of circularly polarized microstrip patch antenna with wide band

characteristics, Springer Verlag Berlin Heidelberg, 2012, 357

[2]R. Joseph* and T. Fukusako,

WITH CIRCULAR SLOT ON CIRCULAR GROUND

Electromagnetics Research C, Vol. 26, 205

[3]Sandeep Kumar, Design of square patch Microstrip antenna for improved bandwidth and

directive gain, International Journal of

2, Issue-2,MAR,2012 , 433-436.

[4]Neeraj Rao,Gain and Bandwidth Enhancement of a Microstrip Antenna using Partial

substrate removal in multiple layer

Sept.12-16, 2011.

[5]Shing-Lung Steven Yang, Ahmed A. Kishk and

U-Slot Microstrip Patch Antenna, IEEE ANTENNAS AND WIRELESS PROPAGATION

LETTERS, VOL. 7, 2008.

[6] Sameh Khmailia, Hichem Taghouti, Riadh Mehouachi and Abdelkader Mami

Of A Rectangular Micro-Strip Antenna By The Scattering Bond Graph

International Journal of Electronics and Communication Engineering &Technology (IJECET)

Volume 3, Issue 1, 2012, pp. 194



330

Directivity of circularly polarized microstrip antenna


successfully implemented. The proposed structure has been simulated by using the Ansoft

HFSS software. The square patch circularly polarized antenna provides enhancement in

return loss (S11 parameters) of -31.53dB is achieved along

n pattern. The circularly polarized microstrip antenna can be used for

AN, IEEE 802.11), as well as military applications.

ong Hee Park,Design of circularly polarized microstrip patch antenna with wide band

Springer Verlag Berlin Heidelberg, 2012, 357-361.

R. Joseph* and T. Fukusako, CIRCULARLY POLARIZED BROADBAND ANTENNA

WITH CIRCULAR SLOT ON CIRCULAR GROUND PLANE , Progress In

ics Research C, Vol. 26, 205-217, 2012 .

Design of square patch Microstrip antenna for improved bandwidth and

, International Journal of Engineering Research and Applications(IJERA)

Gain and Bandwidth Enhancement of a Microstrip Antenna using Partial

substrate removal in multiple layer dielectric substrate, PIER proceedings, Suzhou, Ch

Lung Steven Yang, Ahmed A. Kishk and Kai-Fong Lee, Frequency Reconfigurable

Slot Microstrip Patch Antenna, IEEE ANTENNAS AND WIRELESS PROPAGATION

Sameh Khmailia, Hichem Taghouti, Riadh Mehouachi and Abdelkader Mami

Strip Antenna By The Scattering Bond Graph


194 - 210, Issn Print: 0976- 6464, Issn Online: 0976




proposed structure has been simulated by using the Ansoft

provides enhancement in

31.53dB is achieved along

n pattern. The circularly polarized microstrip antenna can be used for

well as military applications.

ong Hee Park,Design of circularly polarized microstrip patch antenna with wide band

CIRCULARLY POLARIZED BROADBAND ANTENNA

, Progress In

Design of square patch Microstrip antenna for improved bandwidth and

Engineering Research and Applications(IJERA), Vol-

Gain and Bandwidth Enhancement of a Microstrip Antenna using Partial

, PIER proceedings, Suzhou, China,

Fong Lee, Frequency Reconfigurable

Slot Microstrip Patch Antenna, IEEE ANTENNAS AND WIRELESS PROPAGATION

Sameh Khmailia, Hichem Taghouti, Riadh Mehouachi and Abdelkader Mami, “Analyze

Strip Antenna By The Scattering Bond Graph Approach”


6464, Issn Online: 0976 –6472



331

[7] M. Veereshappa and Dr.S.N Mulgi, “Pentagon and Circular Ring Slot Loaded

Rectangular Microstrip Monopole Antennas for Quad-Band Operation” International Journal

of Electronics and Communication Engineering &Technology (IJECET) Volume 4, Issue 2,

2013, pp. 151 - 157, Issn Print: 0976- 6464, Issn Online: 0976 –6472

[8] Amit Kumar Gupta, R.K. Prasad, Dr. D.K. Srivastava, “Design and Development of Dual

E-Shaped Microstrippatch Antenna for Bandwidth and Gain Enhancement” International

Journal of Electronics and Communication Engineering &Technology (IJECET) Volume 3,

Issue 3, 2012, pp. 34 - 42, Issn Print: 0976- 6464, Issn Online: 0976 –6472

[9] Sonia and Satinder Pal, “An Effective Approach to Contention Based Bandwidth Request

Mechanism in Wimax Networks” International Journal of Computer Engineering &

Technology (IJCET) Volume 3, Issue 2, 2012, pp. 603 - 620, Issn Print: 0976 – 6367, Issn

Online: 0976 – 6375

BOOKS:

[10] J. Constantine A. Balanis; Antenna Theory, Analysis and Design, John Wiley & Sons

Inc. 2nd edition. 1997.

[11] Garg, R and Ittipiboon, A; “Micro strip Antenna Design Handbook”, Artech House,

2001.

International Journal of Electronics and Communication … CIRCULARLY... · 2014. 3. 5. · This paper presents a circularly polarized microstrip square patch antenna with single

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