International Journal of Engineering Trends and Technology (IJETT) – Volume 15 Number 4 – Sep 2014
Broadband Microstrip Patch Antenna using Single
U-Slot
Nangare V. M. #1 , Munde K. A. #2, Toshniwal M. B. #3
#1, # 2, #3
M.E. Students, P.G, Department C.O.E. Ambajogai. India
Abstract— In this paper, A single wideband compact microstrip
antenna for high speed WLANs operating in the 5 – 6 GHz
range. By using only single patch a high impedance bandwidth is
achieved. The simulated impedance bandwidth (VSWR<2). This
antenna is fed by a co-axial probe feeding. In this, the effects of
different parameter of antenna are also studied. In this,
analysing rectangular microstrip antenna (RMSA) operating in
5.5 GHz center frequency. The design of a RMSA is made to
several dielectric materials, and the selection is based upon which
material gives a better antenna performance with reduced
surface wave loss. The paper presents a broadband rectangular
Microstrip patch Antenna, with particular attention to high
bandwidth, size reduction and low back lobe radiation in VHF
band. The antenna structure is finally arrived at after studying
various dimensional effects on bandwidth and frequency of
operation. The simulations are conducted using HFSS
(commercial software) and results of the simulation study have
been discussed in the paper.
Keywords— Broadband antenna, Microstrip patch antenna, Uslot antenna.
I. INTRODUCTION
In modern wireless communication systems, multiband
antenna has been playing a very important role for wireless
service requirements. Wireless local area network (WLAN)
have been widely applied in mobile devices such as hand held
computers and intelligent phones. These two techniques have
been widely recognized as a viable, cost-effective, and high
speed data connectivity solution, enabling user mobility with
the rapid development of the modern wireless communication
system, antenna design has turned to focus on wide multiband
and small simple structures that can be easy to fabricate.
With the explosion of the wireless communication systems,
the demand for small size, broadband, high power gain and
efficiency antenna increases considerably broadband for
wireless communications system application suitable for the
5.2-GHz band operations. WLAN has made rapid progress
and 5.2 (GHz) band 4.7328 to 5.5942 (GHz) with the
development of WLAN. Microstrip patch antennas are widely
used because of their several advantages such as light weight,
low volume, low fabrication cost, and capability of dual and
triple frequency operations. However, microstrip antennas
suffer from a number of disadvantages. Narrow bandwidth is a
serious limitation of these microstrip patch antennas. Different
techniques are used to overcome this narrow bandwidth
limitation. These techniques include increasing the thickness
of the dielectric substrate, decreasing dielectric constant, and
ISSN: 2231-5381
using parasitic patches. These techniques have limitations like,
excitation of surface waves and increase in antenna size.
II. ANTENNA DESIGN AND STRUCTURE
A compact broadband microstrip slot antenna is proposed
for WLAN application. The antenna consists of a coaxial feed
line, a substrate, and a ground plane on which some simple
slots is etched. The one U slot is able to achieve high gain and
provide a broadband operation at high frequency. Compared
to the other antennas, the proposed antenna in this later not
only achieves broadband, but also has a rather simple structure
that is easy to fabricate. Meanwhile, the simulated results
represent that the antenna shows a good broadband
characteristic to satisfy the requirement of WLAN in the 5.2GHz band. Details of the antenna design are described in the
later, and simulated results are presented. The exploding
growth of wireless communication systems leads to an
increasing demand for the multilayered laminates broadband
compact low-cost microstrip antennas. The low-profile
multilayer microstrip antennas with a broadband and constant
gain for wireless communication systems are now of great
interest owing to the increase in the data rate. This challenge
is due to the difficulty of obtaining the directional radiation
over a wide impedance bandwidth of the microstrip antenna.
Generally, ordinary wideband microstrip antennas will not
transmit short pulse without distortion.
For high data rate transmission system, we need the
directional wideband microstrip antennas with constant gain
over the wide frequency range. Design of the low-profile
directional microstrip antenna for UWB applications is very
challenging. The printed multilayered antenna can be
integrated into the circuit, and the ground plane can also be
used to isolate the antenna from the other components in the
circuit. Microstrip antennas on a high–low dielectric substrate
combination reduce the element size because of the shorter
wavelengths and also enhance the impedance bandwidth.
Besides, the main drive that reduces the size of the antenna is
able to integrate a patch antenna directly onto a multilayer
circuit board to simplify the interconnection of the antenna
with other circuits. It is well known that one of the most
serious limitations of the basic microstrip antennas technology
is the narrow bandwidth, which is usually around a few
percent. Over the years, many methods have been proposed to
enhance its bandwidth, such as adding an impedance matching
network, using thick and low permittivity substrates, stacked
patches, edge-coupled parasitic patches, lossy materials etc.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 15 Number 4 – Sep 2014
The aperture-coupled microstrip antenna, first proposed by
Pozar has many advantages with a narrow impedance
bandwidth. Zurcher suggested that the bandwidth can be
enhanced by coupling the resonance of the patch close to that
of the aperture resonance. However, this technique introduces
a high backward radiation because of the wide aperture that
radiates on both sides of the ground plane.
These slots are designed to achieve better performance
for the microwave filters and antennas, such as increasing
steepness of the cut-off slope, and to increase the stop band
range of the microwave filters, moreover, compact filter and
antennas can also be achieved using this technique.
Table 1: optimized parameters of geometry shown in Fig. 1.
III. DESIGN FOR THE PROPOSED ANTENNA
The proposed antenna has the single U slot at the middle of
the patch. As shown in Fig. 1 the configuration of the triple
band slot antenna is designed and fabricated on a substrate
with FR 4, relative permittivity of 4.4, and a loss tangent of
0.02. The entire size of the antenna is only 120x90x3.2 mm3.
In the (TMmn mode), the resonance frequency of
antenna given by,
f 
c
2  r
2
2
 m   n  …… (1)

 

 L  W 
Velocity of light given by
c  1/ 0 0
…..……….……………… (2)
The calculation can be improved by adding a “fringing
length extension” L to each edge of the patch to get an
“effective length” Le.
…………………………. (3)
Le  L  2L
And
L  0.5 h
This condition is applied to the proposed antenna W/ L =
1.5
Where the length of the strip, is the effective dielectric
constant, and is the speed of light in free space. The return
loss of the different structures in the antenna design is shown
in Fig. 3 which clearly clarifies the explanation of the
proposed antenna.
Fig. 1: Geometry of proposed antenna
In the given proposed antenna, the dielectric substrate FR 4
is sandwiched between the patch and ground plane. One U
slot is etched on the patch to give high bandwidth. Firstly the
patch antenna is designed to provide a frequency band of 5.5
GHz. One U slot is inserted thereafter in the original patch to
give high BW. This technique is realized by etching slots in
ground plane of the microwave circuit and is namely applied
for the microwave filters. This technique is used for microstrip
and coplanar waveguide transmission lines.
Fig. 2: Simulation setup of proposed antenna.
ISSN: 2231-5381
IV. RESULTS AND DISCUSSION
A. Return loss:
Return loss or reflection loss is the reflection of signal
power from the insertion of a device in a transmission line.
When feed position is taken away from center then return loss
decreases. When the length and width of ground are increases
then return loss increases.
Fig. 3: Simulated Results for Return Loss Vs Frequency (GHz)
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International Journal of Engineering Trends and Technology (IJETT) – Volume 15 Number 4 – Sep 2014
The return loss for the any antenna frequency should be
less than -10dB and the return loss for the given center
frequency 5.5 GHz is -28.21dB.
B. Bandwidth:
It is defined as “The range of usable frequencies within
which the performance of the antenna, with respect to some
characteristic, conforms to a specified standard.” Bandwidth
of the microstrip antenna is closely dependent on the dielectric
substrate, that is also depends on the dielectric constant of
substrate. Low dielectric constant produces high BW. It is also
depends on the probe radius and the height of substrate. As
probe radius and height of substrate increases the BW is also
increases and vice versa.
Fig. 5: Simulated result for input impedance Vs Frequency (GHz)
E. Radiation Pattern:
Bandwidth for the given frequency F1= 5.5 GHz is
Δf1=861.4MHz.
The centre frequency 5.5 GHz resonates between the bands
of 4.7328 to 5.5942 GHz.
C. VSWR:
The value of VSWR should be between one and two for
efficient performance of an antenna.
The antenna pattern is a graphical representation in threedimensional of the radiation of the antenna as the function of
direction. It is a plot of the power radiated from an antenna
per unit solid angle, which gives the intensity of radiations
from the antenna. Antenna gain is the ratio of maximum
radiation intensity at the peak of main beam to the radiation
intensity in the same direction, which would be produced by
an isotropic radiator having the same input power. Isotropic
antenna is considered to have a gain of unity.
Fig. 4: Plot of VSWR Vs Frequency (GHz)
The VSWR for 5.5 GHz is 0.6885.
D. Input Impedance
The input impedance of the microstrip patch
antenna should be in the range of 48-53 ohm. For the better
coupling, the input should be 50 ohm. In addition, the
imaginary characteristic should be less than zero. When the
probe radius increases then the input, impedance decreases.
The input impedance for 5.5 GHz is 51.33 ohm, and the
imaginary characteristic is -3.7.
Fig. 6: Simulated result for the radiation pattern
The proposed geometry is simulated with HFSS software
(pl. ref. its setup in Fig. 2) which is FDTD based
electromagnetic (EM) software.
V. CONCLUSION
The simulated result for input impedance shown in the Fig.
5.
A compact broadband slot antenna for WLAN applications
is presented. Compared to many antennas proposed earlier,
this antenna is designed based on a rather simple structure and
suitable for all frequency bands for WLAN. The proposed
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International Journal of Engineering Trends and Technology (IJETT) – Volume 15 Number 4 – Sep 2014
antenna can be considered to achieve broadband just through
etching slots on the patch, so it can be much easier to fabricate.
In addition, the proposed antenna has good radiation
characteristics and gains in the three operating bands, so it can
emerge as an excellent candidate for multiband generation of
wireless. A prototype is constructed to cover the 5.2 GHz
bands for WLAN operation. The antenna is not only has good
Omni-directional radiation performance, but also has the
advantages of low cost, small size and easy manufacture. For
enhancing bandwidth of microstrip patch antenna is
successfully designed in this research. Simulation results of a
wideband microstrip patch antenna covering 4.7328 to 5.5942
GHz frequency have been presented.
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