Optimizing Rectangular Patch Antenna with Microstrip Line Feed Using Single Stub

Optimizing Rectangular Patch Antenna with Microstrip Line Feed Using Single Stub

Ali Hanafiah Rambe1, Eddy Marlianto2, Nasruddin M.N.3, Fitri Arnia4

1 Department of Electrical Engineering University of Sumatera Utara, Indonesia

2-3 Department of Physics University of Sumatera Utara, Indonesia

4 Department of Electrical Engineering University of Syiah Kuala, Indonesia

Abstract

Antenna microstrip is one of the antenna types that have been chosen to support small and lightweight equipments. However, its performance is poor in conventional form. This paper discussed the

on feed line, the performance of the rectangular patch antenna can be optimized.

2. Antenna Design

The width (W) and length (L) properties of the rectangular patch antenna are given by [1][8][9]:

optimization of a single stub rectangular patch antenna with a microstrip feed line. The simulation results showed an increase in return loss up to 139

%, a 14% increment in bandwidth and a 2% gain

W

2 fr

c

r 1 2

(1)

improvement. The measurement obtained a return loss of -45.61 dB, 106 MHz bandwidth at VSWR

L Leff 2L

c

(2)

2 with about 5.6 dB gain.

Leff

(3)

1. Introduction

2 fr reff

0.3 W 0.264

Microstrip antenna consists of a radiating patch,

reff h

(4)

dielectric substrate, a feed line and a ground plane. Figure 1 shows microstrip antenna configuration.

L 0.412h

0.258 W 0.8

reff

h

Patch

r 1 r 1 1

(5)

Substrate

reff

2 2

112h W

Ground plane

Feed line

Constant c is velocity of light (3×108 m/s), r is the dielectric constant of the substrate, fr is resonant frequency, h is thickness of the substrate, Leff is the effective patch length, L is the length extension and reff is the effective dielectric constant of the

Figure 1. The microstrip Antenna

Microstrip antenna concept was first proposed

substrate.

The characteristic impedance of the narrow microstrip line for w/h 2 is given by [10]:

r

r

by Deschamps in 1953 and got a patent in 1955 for the names of Gutton and Baissinot. The rapid

119, 9 4h

Z ln

4h 2

1/ 2

2

development of microstrip antenna started in 1970s, 20 years later as the dielectric substrates

0 2(

1)

w

(

w

1)

0, 2416

(6)

with a low loss tangent, supportive thermal and mechanical properties were available [1].

Various development and modifications have

r 0, 4516

2(r 1)

and for w/h 2 :

r

been made to the microstrip antenna to improve the

376, 7 w

1

performance, such as array [2], aperture coupled

Z0

h

0,8825 0,1645 r

2

[3], metamaterial [4], defected ground Structure (DGS) [5], photonic bandgap structures (PBG) [6],

r

1

r

w

1

1

(7)

and electromagnetic bandgap (EBG) [7]. This

r 1, 4516 ln

0, 94

paper employed a stub on the microstrip feed line

r

2h

for a rectangular patch antenna. By applying a stub

Where Z0 = characteristic impedance

h = thickness of the substrate

w = width of microstrip line

r = dielectric constant of the substrate

The selected dielectric material for antenna design in this paper is FR4 (r = 4.4 and h = 1.6 mm) and the patch was designed to operate at a resonant frequency of 2.4 GHz. The length and width were calculated to be L = 38.04 mm and W =

28.44 mm. The width of Z0 = 50 line is 3 mm.

1. Simulations and Experimental Result

   The software used to simulate antenna design is the AWR Design Environment. After several trials and errors, the best results were achieved for return loss -11.56 dB and VSWR 1.7187. A single stub was designed to optimize this outcome. Figure 2 and Figure 3 show the variations of the single stub design.

   Figure 2. The variations of stub length

   Figure 3. The variations of stub position After simulating the single stub design, the

   optimum of return loss is found to be -27.66 dB and VSWR is to be 1.0864. Figure 3 and Figure 4 show the comparisons of return loss and VSWR respectively for the antenna design without stub (Rect Feed Line) and with single stub (Rect Feed Line With Stub).

   Figure 4. The comparison of return loss

   Figure 5. The comparison of VSWR

   Based on simulation result, the return loss increases about 139 %. Bandwidth increases from 62.1 MHz (2.4305 GHz 2.3684 GHz) to 70.8 MHz (2.4364 GHz 2.3656 GHz) at VSWR 2.

   Figure 6. The comparison of radiation pattern The comparison of the radiation pattern is

   shown in Figure 6. The gain increases about 2 %. The geometry (in mm) of the designed antenna is shown in Figure 7.

   57

   Patch

   Patch

   60

   60

   40

   40

   Patch

   9

   9

   Mikrostrip line feed

   17

   3

   Figure 9. The simulated and measured VSWR

   From Figure 8, the minimum return loss is – 45,61 dB at frequency 2.380 GHz. Figure 9 shows that the frequency is 2.326 GHz and 2.432 GHz at VSWR 2,. Therefore the bandwidth is :

   FR4

   29

   (a)

   70

   Patch

   Patch

   31

   9

   9

   	Patch		l 11	ine	f	eed	3	Radiatio 0 340 350 6 330 5 320 4 310 3 300 2		n Pattern 10 30 40 50 60
   			4						1
   		29						290	0	70
   FR4								280	-1	80
   									-2

   	Patch		l 11	ine	f	eed	3	Radiatio 0 340 350 6 330 5 320 4 310 3 300 2		n Pattern 10 30 40 50 60
   			4						1
   		29						290	0	70
   FR4								280	-1	80
   									-2

   Mikrostrip

   bandwidth = 2.432 GHz 2.326 GHz = 106 MHz or :

   bandwidth 2.432 GHz 2.326 GHz 100% 4.45 %

   2.380 GHz

   Figure 10 shows the pattern radiation of the measured antenna. The achieved gain is about 5.6 dB.

   60

   60

   40

   <>40

   Stub

   Stub

   27

   27

   20

   	260	100
   Figure 7. Geometry of the designed antenna:	250	110
   (a) without stub (b) with single stub	240	120
   	230	130

   	260	100
   Figure 7. Geometry of the designed antenna:	250	110
   (a) without stub (b) with single stub	240	120
   	230	130

   (b) 270 – 90

   Based on the design given in Figure 7 (b), the antenna was fabricated and measured. Figure 8 and

   9 show the comparison simulated and measured

   220

   210

   200 190

   180

   170 160

   150

   140

   return loss and VSWR from antenna.

   Measured Simulated

   Measured Simulated

   0

   -5

   Return Loss (dB)

   Return Loss (dB)

   -10

   -15

   -20

   -25

   -30

   -35

   -40

   -45

   -50

   2.2 2.25 2.3 2.35 2.4 2.45 2.5 2.55 2.6

   Frequency (GHz)

   14

   13

   12

   11

   10

   14

   13

   12

   11

   10

   9

   9

   8

   8

   VSWR

   VSWR

   Figure 8. The simulated and measured return loss

   Measured Simulated

   Measured Simulated

   7

   6

   5

   7

   6

   5

   4

   4

   3

   3

   2

   2

   1

   1

   2.2

   2.25

   2.3

   2.35

   2.4

   2.45

   2.5

   2.55

   2.6

   2.2

   2.25

   2.3

   2.35

   2.4

   2.45

   2.5

   2.55

   2.6

   Frequency (GHz)

   Frequency (GHz)

   Figure 8. The measured radiation pattern

2. Conclusion

   The rectangular patch antenna with microstrip feed line has been analyzed. The performance of the microstrip antenna can be optimized by using a single stub. The proposed optimization successfully increases the return loss, VSWR, bandwidth, and gain. The measurement demonstrates that the antenna has 106 MHz bandwidth (at VSWR 2) and 5,6 dB gain.

3. References

1. Garg, R., P. Bhartia, I. Bahl, and A. Ittipiboon, Microstrip Design Handbook, Norwood: Artech House. Inc, London, 2001.

2. Muhammad Mahfuzul Alam, Md. Mustafizur Rahman Sonchoy, and Md. Osman Goni, Design and Performance Analysis of Microstrip Array Antenna, Progress In Electromagnetics Research Symposium (PIERS) Proceedings, Moscow, August 2009, pp. 1837-1842.

3. D.M. Pozar, A Review of Aperture Coupled Microstrip Antennas: History, Operation, Development, and Applications. University of Massachusetts at Amherst. 1996.

4. Iftekhar O. Mirza, Shouyuan Shi, Chris Fazi, and Dennis W. Prather, Stacked Patch Antenna Miniaturization Using Metamaterials, IEEE International AP-S Symposium, San Diego. 2008.

5. Y. J. Sung, M. Kim, and Y. S. Kim, Harmonics Reduction With Defected Ground Structure for a Microstrip Patch Antenna, IEEE Antennas And Wireless Propagation Letters, Vol 2, 2003, pp. 111- 113.

6. C.C. Chang, Y. Qian, dan T. Itoh, Analysis And Applications Of Uniplanar Compact Photonic Bandgap Structures, Progress In Electromagnetics Research (PIER), 2003, pp. 211-235.

7. Sreedevi K. Menon, B. Lethakumary, C. K. Aanandan, K. Vasudevan, and P. Mohanan, A Novel EBG Structured Ground Plane For Microstrip Antennas, IEEE Proceedings, 2005, pp. 578-581.

8. Balanis, Constantine A., Antenna Theory : Analysis and Design, Third Edition, Jhon Wiley & Sons, Canada, 2005.

9. Huang, Yi dan Kevin Boyle, Antennas : From Theory to Practice, Jhon Wiley & Sons, United Kingdom, 2008.

10. Focks, E.H. and R. A. Zakarevicius, Microwave Engineering Using Microstrip Circuits, Prentice Hall. Australia, 1990.