Design and Analysis of Single Microstrip Patch Antenna with Proximity Coupler Fed Technique for Wireless LAN Application

IOSR Journal of Electronics and Communication Engineering (IOSR-JECE)
e-ISSN: 2278-2834,p- ISSN: 2278-8735.Volume 10, Issue 1, Ver. II (Jan - Feb. 2015), PP 44-49
www.iosrjournals.org
DOI: 10.9790/2834-10124449 www.iosrjournals.org 44 | Page
Design and Analysis of Single Microstrip Patch Antenna with
Proximity Coupler Fed Technique for Wireless LAN Application
Nuraiza Ismail, Suziyani Rohafauzi, Rina Abdullah, Suziana Omar
(Department of Electrical Engineering / Universiti Teknologi Mara (UiTM), Malaysia)
Abstract: This paper presents an analysis and designing single patch microstrip antenna with proximity
coupler fed technique at 2.4 GHz resonant frequency appropriate for wireless LAN (WLAN) application. The
software used to simulate the patch antenna is Computer Simulation Tools (CST) Microwave Environment. This
antenna is fed by a 50 Ω single microstrip line feeding based on quarter wave impedance matching technique
with width 1.68 mm. In this paper, the effects of antenna parameters like the frequency, return loss, voltage
standing wave ratio (VSWR) and gain (dB) are analyzed by using proximity coupler fed technique. The
construction of the antenna consists of the microstrip feed line on a substrate proximity coupled to a single
rectangular microstrip patch etched in top of surface. The dielectric constant of antenna is 3, the tangent loss
0.03 and thickness of the antenna is 0.76 mm.
Keywords: patch antenna, proximity coupler fed technique, return loss, VSWR, WLAN
I. Introduction
Microstrip antenna have been one of the most innovative topics in antenna theory and design in recent
years, and are increasingly finding application in a wide range of modern microwave systems [1]. It provide
small size antennas as there is much acute space available in these devices due to their compact sizes [2-4]. The
microstrip patch antennas are well known for their performance and their robust design, fabrication and their
extend usage [5]. Microstrip antennas are spreading widely in all the fields and areas and now they are
becoming in the commercial aspects due to their low cost of the substrate material and the fabrication. There are
many applications of microstrip patch antenna due to the increasing of their usage, such as mobile and satellite
communication application, Global Positioning System (GPS) application, Radio Frequency Identification
(RFID) application, radar application, telemedicine application and so on. Microstrip patch antennas are widely
used because of their many advantages, such as the low profile, light weight and conformity. However, patch
antennas have a main disadvantage which is narrow bandwidth [6]. The basic construction of microstrip patch
antenna consists of a radiating patch on one side of a dielectric substrate which has aground plane on the other
side [7].
Recently, wireless local area network (WLAN) applications are very popular. WLANs can achieve
lower transmission latency in the presence of more powerful networks [8] and also capable of providing a high
data rate to the end user. The frequency of 2.4 GHZ offers a data rate up to 11 Mb/s [9].
Microstrip patch antennas have several well-known feeding techniques, which are coaxial probe fed
(CPF), microstrip transmission line fed (TLF), proximity coupled fed (PCF) and aperture coupled fed (ACF). In
proximity coupler fed microstrip patch antennas [10] technique, offer various advantages conventional edge or
coaxial probe fed patches. It allow the patch to exist on a relatively thick substrate for improve bandwidth. The
feed line with thinner substrate reduces the spurious radiation [1] and coupling. An advantage of proximity
coupling is that it provides large bandwidth and low spurious radiation [11]. The dielectric layers need the
proper alignment and increase the overall thickness of the patch antenna.
In this paper, Figure 1 shows the geometric structure of a single patch antenna with proximity couple
fed. The configuration of the proposed antenna consists of two substrates, a top substrate called the antenna
substrate and a bottom substrate called the feed substrate [12]. On the top of feed substrate, the feed line is
designed to have a characteristic impedance of 50 Ω. The bottom of feed substrate has a copper ground plane.
The antenna substrate has a copper patch etched on it.
Figure 1: Geometry of single patch antenna with proximity coupler fed

Design and Analysis of Single Microstrip Patch Antenna with Proximity Coupler Fed Technique ….
II. Antenna Design and Structure
A single patch antenna has been designed with over all dimensions width, W (mm) x Length, L (mm).
The designing of proximity coupler fed patch antenna is set at resonant frequency fr = 2.4 GHz and the dielectric
substrate Taconic RF-30 (loss free) is used. The dielectric constant of the substrate is εr = 3, the tangent loss 0.03
and thickness of the substrate h = 0.76 mm. The width and length of the microstrip antenna are calculated using
following equations.
1
2
f2
V
1
2
f2
1
W
rr
0
roor



 (1)
Where 0V is the free-space velocity of light.
The dimensions of the patch along its length have been extended on each by a distance ,L which is a function
of the effective dielectric constant εreff and the width-to-height ratio (W/h) and the normalized extension of the
length.
2
1
rr
reff
W
h
121
2
1
2
1











 (2)
 
  














8.0
h
W
258.0
264.0
h
W
3.0
h412.0L
reff
reff
(3)
The actual length, L of the patch can be determine as follows
L2
f2
1
L
ooreffr


 (4)
The proposed geometry on Figure 2 shows the five layers for four components which are ground, feed
substrate named as substrate 1, feed line, antenna named as substrate 2 and patch. Feed line placed in between
two substrates, substrate 1 and substrate 2 and used copper material. The bottom line also used copper material
and designed for ground. Figure 3 shows the top view of the proximity coupled fed patch antenna. The width
and length for ground same with the width and length for substrate 1 and substrate 2 which is (88mm X 72 mm).
In the design, a single rectangular patch is etched on the top surface of substrate 2 with the width, W is 44mm
and length, L is 36mm. Both of substrates used Taconic RF 30 (loss Free) with 0.76 mm of thickness, h.
Dielectric constants, εr for these substrates is 3 mm. The microstrip feed line length, Lf is 22mm and the Wf
calculated in order to get the feed line impedance of 50 Ω. The dimensions of the single patch antenna with
proximity coupled fed are shown in Table 1. The single patch antenna with proximity couple is simpler in
construction but to get the frequency of 2.4 GHz and return loss, S11 smaller than -10dB, the dimension of
length, L of patch need to be optimized.
Figure 2: Side view of single patch antenna with proximity coupler

Figure 3: Top view of single patch antenna with proximity coupler
Table 1: Dimensions of the Optimization Antenna
Frequency, fr 2.4 GHz
Patch Copper
W 44.0 mm
L 33.325 mm
Fed Copper
Wf 1.68 mm
Lf 22 mm
Substrate 1, Substrate 2 Taconic RF 30 (loss free)
Dielectric constant, εr 3 mm
Thickness, h 0.76 mm
Tangent Loss 0.03
III. Results and Discussions
The design of this proximity coupler fed patch antenna need to be optimized the length of patch to get
the resonant frequency at 2.4 GHz. Simulation results show that the antenna exhibits three different lengths to
get the resonant frequency. For the first simulation, the value of resonant frequency is 2.233 GHz with length of
33mm. When optimized the length of patch to 31 mm, the resonant frequency is at 2.568 GHz and when
optimized again the length of patch, the resonant frequency is at exactly at 2.4GHz. The length of patch is
optimized to 33.325mm to get 2.4GHz. Figure 4 and 5 show the results for three resonant frequencies of return
loss and VSWR respectively. These results are tabulated in Table 2.
Return loss is the property of an amount of power which is reflected back to the source from an
incorrectly terminated line. It should be as large a negative number as possible. The simulated result shows that
all frequencies have good return loss which is lower than -10 dB.
VSWR is a measure of how much power is delivered to an antenna. The smaller the VSWR is, the
better the antenna is matched to the transmission line and the more power is delivered to the antenna. The
minimum VSWR is 1.0, in which case none of the power is reflected, which is the ideal case. From the VSWR
result, it was observed that the VSWR operated resonant frequency at 2.4 GHz is 1.511.
At resonant frequency of 2.4 GHz, the bandwidth estimated is about 1.3 %. It can be said that the
proposed proximity coupler fed patch antenna operated at narrow bandwidth.
Figure 4: Simulation Result of Return Loss for Three Different Frequencies.
-15
-10
-5
0
2.1 2.2 2.2 2.3 2.3 2.4 2.4 2.5 2.5 2.6
S11(dB)
Frequency (GHz)
S-Parameter Magnitude in dB

Figure 5: Simulation Result of VSWR for Three Different Frequencies.
Table 2: Tabulated Results of Frequency, Return Loss and VSWR
Figure 6 shows the simulated far-field amplitude at three frequency bands. The figure shows that the
maximum gain is 7.437, 7.1 and 6.712 dB at 2.4, 2.568 and 2.233 GHz respectively. Besides, the figure shown
that this antenna has good directional radiation pattern at 2.4 GHz compared to another frequency.
(a)
(b)
(c)
Figure 6: Simulated Far-Field Amplitude at different Frequencies at different of patch length.(a) 2.57 GHz, (b)
2.4 GHz and (c) 2.23 GHz
1
2
4
8
2.1 2.2 2.2 2.3 2.3 2.4 2.4 2.5 2.5 2.6
VSWR
Frequency (GHz)
Voltage Standing Wave Ratio (VSWR)
Length, L (mm)
L=31 L=33.325 L=36
Frequency (GHz) 2.57 2.4 2.23
Return loss, S11 (dB) -13.28 -13.82 -13.57
VSWR 1.511 1.554 1.534

Figure 8 shows the simulated radiation pattern at 2.23, 2.4 and 2.57 GHz.dy9 Half power beamwidth
(HPBW) is the angle between the two directions in which the radiation intensity is one-half value of the beam in
a plane containing the direction of the maximum of a beam. On the other words, the HPBW (-3 dB) is a measure
of the directivity of the antenna.
(a)
(b)
(c)
Figure 7: Simulated Radiation Pattern at (a) 2.23 GHz, (b) 2.4 GHz and (c) 2.57 GHz
A side lobe is a radiation lobe in any direction other than the intended lobe. The side lobe of far field
radiation pattern at 2.4 GHz can be observed in Figure 7(b). The radial distance from the center represents signal
strength. The signal strength for the side lobes is -17.9 dB. It can be observed in Figure 7(b) that the antenna’s
gain is in forward direction (0°) at 2.4 GHz. This is better as compared to 2.23 and 2.57 GHz frequency that
attains to the left and right direction respectively.
IV. Conclusion
The single patch antenna with proximity coupler fed is presented in this paper for coverage standard
IEEE 802.11 in 2.4GHz band resonant frequency. By only adjusting the length of the patch, it can obtain the
desired result at the resonant frequency and satisfactory performances. From the simulation results, it can be
conclude that the antenna operate optimally at resonant frequency 2.4 GHz with good return loss, VSWR and
gain compared to other frequencies.

Acknowledgements
We would like to express our special gratitude to UiTM for support us by giving Dana Kecemerlangan
and UiTM(T), especially Research Management Institute (RMI) unit for the valuable guidance, cooperation and
encouragement in completing this project.
References
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100, 2012,2169-2180.
[3]. S. Maci and G.BGentili, ”Dual-Frequency Patch Antennas” IEEE Antennas and Propagation Magazine, Vol.39, 1997.
[4]. Dau-Chyrh Chang and Cheng-Nan Hu, “Smart Antennas for Advance Communication System”, Proc. IEEE, Vol.100, 2012,2233-
2249.
[5]. Indrasen Singh, Dr. V. S Tripathi “Microstrip Patch Antenna and its Application: a Survey” Int. J. Cmp. Tech. Appl., Vol 2 (5),
1595-1599.
[6]. Fan Yang, Xue Xia Zhang, Xiaoning Ye,Yahya Rahmat –Samii “Wide-Band E-Shaped Patch Antennas for Wireless
Communications” IEEE Transaction on Antenna and propagation, Vol. 49, 2001.
[7]. A. Beno, Dr. D. S. Emmanuel, T. Sidhuj, K. Packia Lakshmi, “ Modified Compact High gain Multiple Patch Slotted Microstrip
Antenna for Multiband wireless communication” International Journal os Scientific & Engineering Research Vol. 2, 2011.
[8]. “ZigBee and wireless radio frequency coexistence,” ZigBee Standards Organization, vol. White Paper, 2007.
[9]. W. Song , H. Jiang, W. Zhuang, and Xuemin Shen , "Resource management for QoS support in cellular/WLAN interworking,"
Network, IEEE , Vol.19, 2005,12- 18.
[10]. D.M.Pozzar and B. Kaufman, “Increasing the bandwidth of microstrip antenna by proximity coupling”, Electronics Letters, Vol. 23,
1987, 368-369,.
[11]. Kshitiz Agarwal, G.P. Rao, M. V. Kartikeyan, M. K. Thumm, “A proximity fed circularly polarized microstrip patch antenna with a
cross slot in the ground plane”, Electronics Letters, Vol. 23, 1987, 368-369.
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Design and Analysis of Single Microstrip Patch Antenna with Proximity Coupler Fed Technique for Wireless LAN Application

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Design and Analysis of Single Microstrip Patch Antenna with Proximity Coupler Fed Technique for Wireless LAN Application