International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 2, Issue 3, March 2013
ISSN 2319 - 4847
ASYMMETRICAL U-SLOTTED
RECTANGULAR MICROSTRIP
PATCH ANTENNA
Amit Khandelwal
Govt. Engineering College, Ajmer, Rajasthan
ABSTRACT
The Microstrip antennas are low profile, mechanically robust, inexpensive to manufacture, compatible with MMIC designs and
relatively light and compact. They are quite versatile in terms of resonant frequencies, polarization, pattern and impedance.
However, the major drawback is its narrow bandwidth and gain. As it is well known that the simple conventional microstrip
antenna has an impedance bandwidth of less than 2 % with low gain of 2 dB. In this paper, bandwidth of microstrip antenna is
increased by introducing a slot of U shape. The Ansoft HFSS 11 is used for the simulation .The antenna is fed by coaxial probe
feeding technique. The designed antenna provides the bandwidth of 300MHz (5.61GHz-5.91GHz) with return loss of -26.26db
at 5.76GHz and 310 MHZ (6.36GHz-6.67GHz) with return loss of -24.12db at 6.48GHz.VSWR is 0.82 at 5.76GHz and 1.03 at
6.48GHz.
Keywords: Slotted Microstrip Antenna, VSWR, Return loss, Gain, HFSS
1. INTODUCTION
A microstrip antenna consists of conducting patch on a ground plane separated by dielectric substrate. Low dielectric
constant substrates are generally preferred for maximum radiation. The conducting patch can take any shape but
rectangular and circular configurations are the most widely used shapes. A feed line is used to excite patch antenna to
radiate by direct or indirect contact. Four most popular methods are micro strip line feed, coaxial probe, aperture
coupling and proximity coupling [1]. In this paper, antenna is fed by coaxial probe feeding techniques. The microstrip
patch antenna in the basic form of a conducting patch in a grounded substrate is inherently narrowband and is not able
to meet the requirements of wireless communication systems. Whereas bandwidth can be increased by using lossy
substrates, this is usually not desirable as efficiency will be reduced. The methods developed for efficient wideband
patch antenna design are based on one or more of the following principles:
a) By means of parasitic elements or slots, additional resonances are introduced so that, in conjunction with the main
resonance, an overall broader band response is obtained.
b) Thick substrates of low permittivity are used
Loading specific slot on the conducting patch element of antenna, reduced size with improvement in bandwidth, gain
can be obtained [2]. The loading of slots on the conducting patch element can cause meandering of the excited patch
surface current paths and results in lowering of the resonant frequency, which corresponds to the reduced antenna size
compared to the conventional microstrip patch antenna at designed frequency. In this paper, study is made that by
loading slots on the conducting patch element with thick dielectric medium excited through single coax feed
arrangement providing improvement in antenna impedance bandwidth, gain with size reduction characteristics.
The impedance bandwidth is increase with substrate thickness t and inversely proportional to [3].
BW ~ volume = area× height = length ×width ×height
~
× ×
=
Impedance Bandwidth of patch antenna varies inversely as Q of a patch antenna [4]. Therefore substrate such as
dielectric constant
and thickness h can be varied to obtain different Q,and ultimately the increase in impedance
bandwidth Q of a resonator is defined as
Q=
Volume 2, Issue 3, March 2013
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International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 2, Issue 3, March 2013
ISSN 2319 - 4847
2. DESIGN
I)
DESIGN FORMULA
A. Calculation of the Width (W):
The width of the Microstrip patch antenna is given by equation (1):
W=
(1)
Where c is the velocity of light.
B. Calculation of Effective dielectric constant
=
+
[1+12 ] -1/2
C. Calculation of the Effective length (
=
(2)
):
(3)
D. Calculation of the Length Extension (ΔL):
(4)
E. Calculation of actual length of patch (L):
L=
-2 L
(5)
II) DESIGN SPECIFICATIONS
Figure 1 Top view of Slotted Rectangular Microstrip Patch Antenna
In this design two different dielectric material i.e. Rogers RT/duriod 5880 ( = 2.2, h= 4.2 mm, tanδ=0.0009) and pec
material ( =1.00) was used.
Table 1: Antenna dimensions
S. No.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Antenna parameters
Length of the Substrate (L)
Width of the Substrate (W)
Length of the Patch (L)
Width of the Patch (W)
Height of the Substrate (h)
Distance from Feed(F)
Length of U slot arm(U1)
Length of U slot arm(U2)
Length of U slot arm(U3)
Width of Slot(W1)
Volume 2, Issue 3, March 2013
Specification
78mm
78mm
40mm
40mm
4.2mm
8.45mm
16.9mm
28.8mm
22.3mm
2.3mm
Page 82
International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 2, Issue 3, March 2013
ISSN 2319 - 4847
3. RESULTS & DISCUSSION
The Asymmetrical U-slot antenna of parameters listed in Table I has been fabricated and measured to compare the
simulated results. The bandwidth of 300MHz (5.2%) with return loss of -26.52db at 5.76GHz and 310 MHZ(4.7%)
with return loss of -24.12db at 6.48GHz. Simulated results for U slot probe feed patch antenna is shown Table 2.
Table 2: Simulated results for U slot probe feed patch antenna
Patch
Frequency
Gain
Shape
Return
VSWR
Bandwidth
-26.26dB
0.82dB
5.61GHz-5.91GHz
-24.12dB
1.03dB
6.36GHz-6.67GHz
Loss
U Shape
5.76GHz
9.283d
B
6.48GHz
XY Plot 1
Ansoft Corporation
HFSSDesign2
0.00
Curve Info
dB(St(Coax_Pin_T1,Coax_Pin_T1))
Setup1 : Sw eep1
d B(St(Co ax_ Pin _T1,C oa x_ Pin _T1))
-5.00
-10.00
-15.00
-20.00
-25.00
-30.00
3.00
3.50
4.00
4.50
5.00
Freq [GHz]
5.50
6.00
6.50
7.00
Figure 2 Return losses vs. Frequency curve for proposed antenna
Ansoft
NameCorporation
X
35.00
m1
5.7600
XY Plot 3
Y
HFSSDesign2
0.8240
Curve Inf o
dB(VSWRt(Coax_Pin_T1))
Setup1 : Sw eep1
d B(VSWR t(C o ax_ Pin _T1 ))
30.00
25.00
20.00
15.00
10.00
5.00
m1
0.00
3.00
3.50
4.00
4.50
5.00
Freq [GHz]
5.50
6.00
6.50
7.00
Figure 3 VSWR for proposed antenna
VSWR is 0.82 at 5.76GHz and 1.03 at 6.48GHz obtained.
Volume 2, Issue 3, March 2013
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International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 2, Issue 3, March 2013
ISSN 2319 - 4847
Radiation Pattern 1
Ansoft Corporation
HFSSDesign2
Curve Info
0
-30
dB(GainTotal)
Setup1 : LastAdaptive
Phi='0deg'
30
0.00
dB(GainTotal)
Setup1 : LastAdaptive
Phi='90deg'
-10.00
-60
60
-20.00
-30.00
-90
90
-120
120
-150
150
-180
Figure 4 Radiation Pattern
The radiation Pattern with maximum gain of 9.283db is shown in figure 4.
4. CONCLUSION
In this paper, Small dual band for asymmetrical U-slotted rectangular micro strip patch antenna is designed. The probe
feed technique is used and simulation is performed and validated on HFSS11’ [5]. The parameters, such as gain,
VSWR, return losses etc. are taken for the consideration and are shown in the Table 2. The conclusion is that these
parameters are satisfactory for these bands. The antenna is designed to be used in WiMax and multi-band applications.
REFERENCES
[1] Constantine A. Balanis, ‘Antenna Theory, Analysis and Design’ (John Wiley & Sons)
[2] Kin-Fai Tong and Ting-Pong Wong, “Circularly Polarized U-Slot Antenna” IEEE Transactions on Antennas And
Propagation, Vol. 55, No. 8, August 2007
[3] K. F. Lee and K. F. Tong, “Microstrip patch antennas- Basic Characteristics and Some recent Advances” Proc.
IEEE. December 13, 2011.
[4] Ramesh Garg, ‘Handbook of Microstrip Antennas
[5] Ansoft Designer, www.ansoft.com.
AUTHOR
Amit Khandelwal did his B.E. in Electronics and Communication Engineering from University of Rajasthan,
Jaipur, Rajasthan. He is doing M.Tech. in Electronics and Communication at Govt. Engineering College, Ajmer,
Rajasthan
from Rajasthan Technical University, Kota, Rajasthan. His research areas are DIGITAL
COMMU1NICATION.
Volume 2, Issue 3, March 2013
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