Bandwidth Enhancement of Microstrip Patch Antenna Using Parasitic Patch Configuration

Paritaba B Parmar Shantilal Shah Engg. College,

Gujarat, India reshma.maths@gmail.com

Balvant J Makwana Government Engineering College,

Gujarat, India balvantmakwana@gmail.com

Mehul A Jajal Shantilal Shah Engg. College,

Gujarat, India mehul jajal@gmail.com

Abstract—The author has simulated microstrip patch antenna with prime focus of increasing bandwidth using various techniques of probe feed, parasitic patch around the main patch and two layer of substrate. The simulation process has been done using HFSS (High Frequency Structural Simulator). In this paper, authors cover five aspects of microstrip antenna designs. The first is the analysis of single element narrowband rectangular microstrip antenna which operates at the central frequency of 2.4 GHz. The second/third aspect is the analysis and design of two gap/direct coupled parasitic patch along radiating edge of main patch and in forth/fifth aspect is the analysis and design of two layer of substrate on parasitic patch design. The properties of antenna such as bandwidth, S parameter, VSWR, Gain has been investigated and compared. Keywords- Bandwidth; HFSS; MSA; Parasitic Patch; Return loss

I. INTRODUCTION

With the rapid growth of the wireless mobile communication technology, the great demands in future technologies are very small size wide band antennas. For this Microstrip patch antenna is the better part. Microstrip patch antenna becomes very popular nowadays because of its ease of analysis and Fabrication, low cost, light weight, easy to feed and their attractive radiation characteristics. Although microstrip patch antenna has numerous advantages, it has inherent limitation of narrow bandwidth, low gain. To overcome its inherent limitation of narrow impedance bandwidth and low gain, many techniques have been suggested and investigated for MSA. We can mention multilayer structures [2], broad folded flat dipoles [3], curved line and spiral antennas [4], impedance matched resonator antennas [5], resonator antennas with capacitive coupled parasitic patch element [6], log periodic structures [7, 8], modified shaped patch antenna (H-shaped [9]).In the present paper Parasitic patches along main patch type microstrip patch antenna analyzed and compared with rectangular patch antenna.

II. MSA WITH SINGLE PATCH

A microstrip patch antenna in its basic form consists of a metallic radiating patch on one side of dielectric substrate, which has a ground plane on other side. The radiating elements and feed lines are usually photo etched on the dielectric substrate [1].

The pertinent design parameters are given together with

their relevant equations to allow basic ‘hand’ calculations before simulation is attempted. By using this flow of design, simple microstrip patch antenna can implemented. A single element of rectangular patch antenna, as shown in figure 1, can be designed for the 2.4 GHz resonant frequency using transmission line model (step 1, 2, 3).

In the typical design procedure of the microstrip antenna

using transmission line model, the desired resonant frequency, thickness and dielectric constant of the substrate are known or selected initially. In this design of rectangular microstrip antenna, Rogers RT/duriod 5880 (tm) dielectric material is selected as the substrate with 0.32cm height. Then, a patch antenna that operates at the specified resonant frequency (2.4 GHz) can be designed by the using transmission line model equations [1]. As shown in figure 2, coaxial probe type feeding mechanism used. The rectangular microstrip patch antenna parameters are: Resonating frequency fr = 2.4 GHz Patch width W = 3 cm Patch length L = 4 cm Substrate height h = 0.32 cm Relative permittivity �r = 2.2 Probe radius rp= 0.07 cm Coaxial radius rc= 0.16cm Probe position = (-0.5, 0.1, 0)

2012 International Conference on Communication Systems and Network Technologies

978-0-7695-4692-6/12 $26.00 © 2012 IEEE

DOI 10.1109/CSNT.2012.21

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2012 International Conference on Communication Systems and Network Technologies

978-0-7695-4692-6/12 $26.00 © 2012 IEEE

DOI 10.1109/CSNT.2012.21

54

2012 International Conference on Communication Systems and Network Technologies

978-0-7695-4692-6/12 $26.00 © 2012 IEEE

DOI 10.1109/CSNT.2012.21

54

2012 International Conference on Communication Systems and Network Technologies

978-0-7695-4692-6/12 $26.00 © 2012 IEEE

DOI 10.1109/CSNT.2012.21

54

2012 International Conference on Communication Systems and Network Technologies

978-0-7695-4692-6/12 $26.00 © 2012 IEEE

DOI 10.1109/CSNT.2012.21

54

2012 International Conference on Communication Systems and Network Technologies

978-0-7695-4692-6/12 $26.00 © 2012 IEEE

DOI 10.1109/CSNT.2012.21

54

2012 International Conference on Communication Systems and Network Technologies

978-0-7695-4692-6/12 $26.00 © 2012 IEEE

DOI 10.1109/CSNT.2012.21

53

2012 International Conference on Communication Systems and Network Technologies

978-0-7695-4692-6/12 $26.00 © 2012 IEEE

DOI 10.1109/CSNT.2012.21

53

2012 International Conference on Communication Systems and Network Technologies

978-0-7695-4692-6/12 $26.00 © 2012 IEEE

DOI 10.1109/CSNT.2012.21

53

Figure 1. Design Flow Steps

III. WHY WE USED PARASITIC PATCH

In each antenna type, a design accounted according to the bandwidth. Bandwidth can be increased by increasing the height of the antenna. However, there are some limitations on how high the antenna can be. Current applications require the antenna volume to be small. Therefore, increasing the height of the antenna may not satisfy the size specifications for the required bandwidth. However, performance can be degraded when the height is increased. If a substrate is used in the microstrip antenna, one can increase the bandwidth by lowering its dielectric constant value. Such a behavior for microstrip antennas where the unloaded Q is proportional to �r and the bandwidth is inversely proportional to Q. However, increasing the bandwidth using this technique can cause some practicality issues such as increase in antenna cost.

A technique for improving the bandwidth of low-profile

antennas that does not significantly increase the volume or degrade the performance is to use parasitic elements. Parasitic elements are designed to resonate close to the resonant frequency of the driven radiator element, leading to a desirable tuned response. The result is a wider effective impedance bandwidth of the antenna. It is also called

double-resonance phenomenon technique. With this same design, Two layer of substrate is used which increase the substrate thickness leads to excitation of surface waves.

IV. GAP/DIRECT COUPLED PARASITIC PATCH ALONG MAIN PATCH

The patch antenna consist of two parasitic patches along

radiating edge of the main patch; supported on a grounded dielectric sheet of thickness h and dielectric constant �r. Parasitic patch antenna reported here has a size about same that of the rectangular patch, with better bandwidth. The position of the probe feed is change because of the impedance matching. Gap/Direct coupled parasitic patch antenna is shown in figure 3, 4 Design parameters of Gap/Direct coupled parasitic patch antenna The length � and width � of the patches is: L = 4 cm; W = 3 cm; fr = 2.4 GHz The chosen substrate is Rogers RT/duriod 5880 (tm) relative permittivity �r =2.2 and height h = 0.32 cm Probe position in gap couple design= (-1.1, 0, 0) Probe position in direct coupled design= (1.5, 0, 0) In both design as shown in figure 9 and figure 10, bandwidth is enhanced comparatively to single patch antenna design because using gap coupled, the effective aperture is increased and using direct coupled the physical size increased. The dimensions and location of the parasitic patch play important role in obtaining the wide bandwidth for the proposed antenna as distance between radiators Patch and the parasitic patch along radiating side on the impedance bandwidth of antenna. Actually the separation distance d is very small but variation in it affects the input impedance of an antenna. Here the distance between them is 0.3cm.

V. TWO LAYER OF SUBSTRATE IN PARASITIC PATCH ANTENNA

Using single patch or parasitic patch, bandwidth enhance

up to very low percentage. With the two layer of substrate, surface wave of the antenna is decrease and we can improve the bandwidth with good result compared to single patch. Here we have assigned perfect E boundary for patch and ground plane. Vacuum, for air box and RT/duriod 5880 (tm) is used for substrate1. We used another substrate on patches that is having same dielectric constant, to minimize radiations to be lost in space which is shown in figure 5 and figure 6.

In both design, dimension of patch, ground and substrate 1 is same. Height of substrate 2 is 0.64 cm. The position of

Input f0, h and �r

0

22 r e f f

cL Lf ε

= − Δ

Where,

( )( )

0 .3 0 .2 6 40 .4 1 2

0 .2 5 8 0 .8

Wr e f f h

L h Wr e f f h

ε

ε

� �+ +� �� �Δ =

� �− +� �� �

11 1 21 122 2

hr rreff w

ε εε

−+ − � = + + ��

( )0

12

2r

cWf

ε=

+

End

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probe is changed because of impedance matching. Result of this design is best one compared to other designs in gap coupled part.

V: RESULTS

The simulated result of S11 scattering parameter (return loss) of single element rectangular microstrip antenna is presented in figure 7. From the figure, the antenna has almost 2.36GHz resonant frequency and it has 50MHz bandwidth at 10 dB (the difference of 2.38 GHz and 2.33 GHz). In percentage, the bandwidth of the antenna is 2.1%.

In Gap/Direct Coupled Parasitic Patch microstrip antenna, the simulated result of S11 scattering parameter is presented in figure 8 and figure 9. From the figure 8, the antenna has almost 2.30GHz resonant frequency and it has 50MHz bandwidth (the difference of 2.27 GHz and 2.32 GHz). In percentage, the bandwidth of the antenna is 2.18%. From the figure 9, the antenna has almost 2.33GHz resonant frequency and it has 80MHz bandwidth (the difference of 2.28 GHz and 2.36 GHz). In percentage, the bandwidth of the antenna is 3.43%.

In Two layer of substrate in gap coupled parasitic patch microstrip antenna, the simulated result of S11 scattering parameter is presented in figure 10 and figure 11. From the figure 11, the antenna has almost 2.54GHz resonant frequency and it has 270MHz bandwidth (the difference of 2.38 GHz and 2.65 GHz). In percentage, the bandwidth of the antenna is 10.62%. From the figure 11, the antenna has almost 2.20GHz resonant frequency and it has 90MHz bandwidth at 10 dB (the difference of 2.14 GHz and 2.23 GHz). In percentage, the bandwidth of the antenna is 4.10%.

VI: CONCLUSION

In this paper, 4x3cm rectangular microstrip patch antenna fed with contacting method using probe feed contemporary technique. The rectangular MSA presented with RT/duriod 5880 (tm) substrate and thickness h=0.32 cm and got return loss bandwidth 2.1%. In two layer of substrate in parasitic patch antenna presented and got 10.62% bandwidth. Main reason of bandwidth improvement is the effective aperture area is increased and the surface wave is decrease. So by using Parasitic Patch with two layer of substrate MSA instead of rectangular MSA we can get bandwidth improvement.

TABLE I. COMPARISON BETWEEN RECTANGULAR AND PARASITIC PATCH MSA

Design Return

Loss Gain VSWR Bandwidth

Single patch

-32.24db 6.6db 1 2.1%

Gap coupled

-12.53db 4.9db 1.7 2.18%

Direct coupled

-19.60db 5db 1.27 3.43%

Double layer sub. in direct

coupled -16.31db 4.7db 1.36 4.10%

Double layer sub. in gap

coupled -37.62db 8.9db 1.02 10.62%

REFERENCES

[1] Constantine A. Balanis: “Antenna Theory, Analysis and design” (John Wiley & Sons) [2]. Hall, P. S. Wood, C and Garrett, C, �“Wide bandwidth microstrip antennas for circuit integratio”, Electron. Lett. , 15, pp. 458-460, 1979. [3]. Dubost, G., Nicolas, M. and Havot, H. �“Theory an applications of broadband microstrip antenna”, Proceedings of the 6th European Microwave Conference, Rome, pp. 21S—219, 1976. [4]. Wood, C,� “Curved microstrip lines as compact wideband circularly polarised antenna”, IEE J. Microwaves, Opt. & Acoust, 3, pp. 5-13, 1979. [5]. Van De Capelle, A., De Bruyne J., Verstraete, M., Pues, H. and Vandensande J. �“Microstrip spiral antenna”, Proceedings of the International IEEE Symposium on Antennas and Propagation, Seattle, pp. 383-386, 1979. [6]. Pues H. F. and Van De Capelle A. R. �“Impedance-matching of microstrip resonator antennas”, Proceedings of the North American Radio Science Meeting, Quebec, p. 189, 1980. [7]. H. Pues, Ir., J. Bogaers, Ir., R. Pieck, Ir. and A. Van de Capelle, Dr. Ir. �“Wideband quasi-log-periodic microstrip antenna”, IEE PROC, Vol. 128, Pt. H, No. 3, , pp. 159-163, June 1981. [8]. V. B. Romodin, V. I. Oznobikhin and V. V. Kopylov, �“Log Periodic Microstrip Array”, IEEE - Russia Conference, Mia-Mep9, 1999. [9]. Ravi Kant and D.C.Dhubkarya, �“Design & Analysis of H-Shape Microstrip Patch Antenna”, publication in the �Global Journal of Research in Engineering, Vol. 10 Issue 6 (Ver 1.0), pp. 26-29, Nov. 2010.

Figure 2. Rectangular MSA with single patch.

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Figure 3. Gap coupled parasitic patch antenna.

Figure 4. Direct coupled parasitic patch antenna.

Figure 5. Two layer substrate on gap coupled

parasitic patch antenna.

Figure 6. Two layer substrate on direct coupled

parasitic patch antenna.

Figure 7. Return loss of MSA with single patch element

Figure 8. Return loss of gap coupled patch along main patch.

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Figure 9. Return loss of direct coupled patch

along main patch.

Figure 10. Return loss of two layer of substrate in

gap coupled parasitic patch antenna.

Figure 11. Return loss of two layer of substrate in

direct coupled parasitic patch antenna.

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