Omni-Directional Coplanar Feed S-Band Printed
Monopole Antenna Array for WLAN
Ashwini Kumar Singh
Electronics and Communication Engineering
MANIT Bhopal
Bhopal, India
araghuvanshi.2008@gmail.com
Dheeraj Agrawal
Electronics and Communication Engineering
MANIT Bhopal
Bhopal,India
profdheerajagrawal@gmail.com
Abstract—Wideband
monopole
antenna
having
omnidirectional radiation pattern coplanar feed printed on same
plane is proposed for S-Band application. Proposed Antenna is
able to resonate the 3.4GHz frequency which accommodate in the
spectrum at S band where wide use of WLAN and WiMAX is
utilizes. In recent technologies wide band antennas have become
challenging subject comparing with the other techniques of
antenna designing the microstrip antenna large beneficial- these
antennas have compact size, wide bandwidth, structures are very
simple in designing. Return loss result where impedance
bandwidth reaches 2.2 GHz to 3.8 GHz frequency range which is
wide bandwidth in antenna resonance property.
made in middle, which seems quite rectangular ring in shape
that helps antenna to enhance its bandwidth [4].
The coplanar wave (CPW) feed is provided to the patch [5].
The CPW has 50 ohm impedance to match the patch antenna.
The base layer of patch antenna is non regular in shape, which
is situated below the substrate. It reduces the shape and size of
patch with shift in frequency range towards right. There are
many simulations to achieve the results of proposed antenna.
To simulate all these mentioned antennas we used the CST
microwave software.
Keywords- coplanar feed(CPW), impedance bandwidth, Monopole
antenna, CST, radiation Field.
The rectangular ring with coplanar waveguide feed as shown
in figure 1. The antenna geometry consists of a patch,
substrate, defected ground [6], and the coplanar waveguide
feed. The design is, in such a way that patch and the coplanar
wave guide is printed on same plane and substrate also has the
single layer which makes antenna very simple to design
[7].The single layer of a metallic structure and the substrate
makes
the
proposed
antenna
very
inexpensive.
I
INTRODUCTION
.
Miniaturization of electronic devices has become main focus
in recent development of technology. The electronics devices
working on radio frequency required an efficient antenna
design[1] while reducing the size of antenna. The features
directivity, gain , radiation pattern should also be maintained
while reducing the size of antenna. To get all these properties
in a single antenna very few studies have been done on Omnidirectional field and high radiation efficiency qualities.
II
ANTENNA CONFIGURATION
Antenna arrays are the basic constituents of smart antenna.
The application of multiple elements enable these to produce
the radiation characteristics [2]. The ability of an antenna
array to steer or point its beams in the direction of the users
in one of its most desire features [3]. If the number of
rectangular cut slot patch antenna is increased, bandwidth can
increase or decrease.
In this paper, we have proposed a two antenna array that
shows wide bandwidth at calculated frequency of 3.4 GHz. In
this method we have achieved 1.3 GHz impedance bandwidth,
so it can be utilized for other frequencies. The patch is
rectangular in shape, in which wide rectangular cut slot is
Fig. 1. Geometry of the proposed antenna Front view
The antennas patch is a perfect electric conductor material
(PEC), which radiates omnidirectional electric and magnetic
fields in space mounted above the substrate. The patch length
is 50mm and 50mm wide. These dimensions are achieved by
the formulae of microstirp antenna designing [1], [8]. The
fringing fields along the width can be modeled as radiating
slots and electrically the patch of the micro strip antenna looks
greater than its physical dimensions.
radiation into space, but at the expense of larger element size .
The material chosen for substrate is FR4 [11] which is lossy in
nature. The electric permittivity value of substrate is 4.4 and
this material is easily available. The size of the substrate is
larger than patch and ground, its length and width is 50mm
each having the height of 3mm.
𝐿𝑒𝑓𝑓 = 𝐿 + 2 × 𝞩𝑳
𝞩𝐿 = ℎ × 0.42
Ɛ𝑒𝑓𝑓 =
Ɛ+1
2
(Ɛ + 3)((𝑤/ℎ) + 0.264)
𝑤
(Ɛ − 0.258)(( ) + 0.8)
ℎ
+
Ɛ−1
2
×
1
2
√1 + 12 × ℎ
𝑤
In the above formula L is actual length and 𝐿eff is effective
length of the patch. ∇L is expansion in length of antenna.
Ɛ𝑒𝑓𝑓 is effective electric permittivity of substrate. 𝑤 is width
of substrate and ℎ is the height . This formula is designed for
determining the actual length and width of the patch. This
designed antenna at centre frequency of 3.4 GHz has wider
bandwidth where wide use of WLAN and WiMAX [9], [10].
Fig. 3. Geometry of the proposed antenna Back view.
The ground is placed below the substrate which is modified
ground structure [6],[12] which is perfect electric conductor
quality, during simulation this type of structure shifts the
frequency bandwidth. The length of the ground in y-direction
is 30mm and width at x-direction is 50mm which is layered at
the bottom of substrate.
Coplanar waveguide is provided for excitation of electric field
to patch [13], CPW is fixed at the same surface of patch. CPW
feed is symmetric in dimension, which is matched to 50 ohm
input impedance. By application of CPW introduces the
resonance at the frequency of 3.4 GHz and can be optimized
to extend the bandwidth for the antenna which is done in this
paper. The achieved length of the CPW is 30mm and the
width is 4mm, in this feed line inset feed cut is given, which
helps antenna for perfect impedance matching point [14].
These inset feed slits have the dimension of 2mm length and
1mm width
Fig.4 inset feed
For designing of patch , copper metal is used which is lossy in
nature and perfect electric conducting (PEC) property . Its
electric and thermal conductivity are 5.8e+007[s/m] and
401[w/k/m] respectively. In the rectangular patch there is
rectangular slot is cut away which reduces the total metal area
of patch and helps in impedance matching. The size of slot is
18.32 mm long and 24.84mm wide which is etched out from
middle.
Substrate is placed between the patch and the ground, the
surface waves concentrate in it which helps antenna energy to
intensify. There are numerous substrates that can be used for
the design of microstrip antennas and their dielectric constants
are usually in the range of 2.2 < Ɛ𝑟 < 12 . Most desirable for
good antenna performance are thick substrates , dielectric
constant is in the lower end of the range because they provide
better efficiency, larger bandwidth, loosely bound fields for
TABLE FOR ANTENNA DIMENTION
Parameters
Substract Length
Substract Width
Substract Height
Ground Length
Ground Width
Patch Length
Patch Width
Feed Length
Feed Width
Inset Slit s1
Inset Slit s2
Port
SL
SW
SH
GL
GW
PL
PW
FL
FW
S1
S2
Dimensions in mm
50
50
3
30.1
50
20.32
26.84
30
4
2
1
Discrete
III
SIMULATED
ELEMENT
RESULTS
OF
SINGLE
RETURN LOSS
Fig. 7. Simulated electric field of single element antenna at 3.5 GHz
Fig. 5. Simulated and measured return losses of single element antenna.
3- D PATTERN :-
VSWR
Fig.6 simulated 3-D Pattern of single element antenna
Electric field Intensity in patch :-
Fig. 8. Simulated VSWR of single element antenna
E- FIELD :-
designed in the single substrate and ground material, the
design dimensions below-
Parameters
Substrate length
Substrate width
Substrate height
Ground Length
Ground Width
SAL
SAW
SAH
GAL
GAW
Dimensions in mm
50
100
3
30
100
The simulation results of antenna at high frequency
able to radiate at omi-directional field pattern the features
shows the antenna has capability to perform in wireless
communication system environment. Three dimensional
radiation pattern is shown belowH- FIELD :V
SIMULATION RESULTS OF ARRAY
RETURN LOSS
Fig. 9. Simulated and measured radiation patterns of single element antenn a
at 3.5 GHz
IV
TWO ELEMENT ARRAY DESIGNING
Fig. 11. Simulation result of return loss for 2 element array antenna
.
3-D PATTERN :-
Fig. 10. Geometry of two element array antenna
After simulation and optimization of single element antenna,
Two element antenna array is analyzed in CST microwave
software. Two elements antenna is achieved by placed single
element antenna side by side having distance of lambda
wavelength , both the antennas are excited simultaneously so
the single radiation pattern is achieved. Antenna array is
Fig. 12 3- D pattern of 2 element array antenna
E- FIELD :-
conclude the best element for the use in our field. Seeing
the result element two and four they both have the
approximately similar bandwidth but they have different
values for Gain and Directivity, on Single Element of
antenna shows the very less bandwidth in comparison to
above two elements where it gives deepest dip of S11
return loss. The Array Design of Three and Four
elements models are shown below.
H- FIELD :-
Fig. 14. Geometry of 3 element array antenna
Fig. 13. Simulated and measured radiation patterns of 2 element array
antenna at 3.5 GHz
The above Array of three elements is shown above have
the three patches and three ground surfaces where single
substrate is placed between them they all are kept in side
by side. The Dimension of patch and ground are already
defined the dimension substrate has been increased due
to arrangement of array which is 170mm and no of port
are also increased by three. And array of four elements
is shown below which consist of four ground and four
patches elements, where it also consists four port whose
result parameters are shown in table no. The dimensions
of patch and ground are predefined but here substrate
width and length is 100 mm respectively
PARAMETER OF BOTH ANTENNA
Parameter
Bandwidth
Gain
Directivity
Return Loss
Radiation Efficiency
VI
SingleElement
424 MHz
4.1 dB
4.6 dB
-40 dB
-0.56 dB
Array Antenna
1.18 GHz
5.4 dB
5.9 dB
-27 dB
-5.4 dB
DESIGN OF THREE AND FOUR ELEMENT
ARRAY ANTENNA
After the analysis of single and double element of the
model is simulated with the three and four elements,
where these two are also the array of single elements.
The table below shows the comparative results for
all the four antenna, they all are discredited by results of
s11 return loss. Each Antenna gives the different
radiation pattern and s11 results. As by the table we can
Fig. 15. Geometry of 4 element array antenna
four antennas two element antenna is use for mobile
communication. So two array element antenna is best use for
mobile communication.
CONCLUSION
These planar antennas are very easily manufactured and it’s
fabrication from dielectric block for commercial use is
convenient. Slot technique provides better impedance, which
is shown in simulated
design. For the application
commercially slotted patch launches electric field as high
efficient. Achieved gain over the range of S-band is attractive
feature for antenna. This designed radio Antenna is for high
power where Rf efficient radio equipped to transmit over
3.4GHz also compatible for various purposes. These results
shows antennas could be developed for possible applications
in several wireless systems like Wireless/PCS, Sattellite
Radio , GPS, Sirius, WLAN ,Wide-Band RF Transmission
and Antenna Remoting if properly scale to the allowed
frequency bands. If the number of antenna is increases on a
single substrate then bandwidth decrease and size increases.
Fig. 16. Simulated result of return loss for different antenna
REFERENCES
,
[1]
COMPARISION OF ANTENNA ELEMENTS
Parameters
Frequency
Band
Feed method
Bandwidth
BW Range
Gain
Directivity
ReturnLoss
Rad. Effc.
Substrate
Applicat n
I- Element
3.5GHz
S
Coplanar
420MHz
3.2-3.6 GHz
4.17 dB
4.8 dB
-40.64
-0.66 dB
Ɛr-4.3
Wireless,
Mobile,GPS
VII
II-Element
3.5GHz
S
Coplanar
1.2GHz
2.5-3.7GHz
5.43dB
5.97dB
-27.23
-0.54 dB
Ɛr-4.3
Wireless,
Mobile,GPS
III-Element
3.5 GHz
S
Coplanar
120MHZ
3.2-3.6GHZ
5.4
5.7
UnMatched
-0.8026
-------------
IV-Element
3.5 GHz
S
Coplanar
1Ghz
2.6-3.6Ghz
5.74 dB
6.31dB
-23
-0.83
Ɛr-4.3
Wireless,
Mobile,GPS
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Sons, 2005.
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RESULT AND DISCUSSION
Fig.16. represents simulated and measured losses of the four
different proposed antenna . For the measured results , relative
impedance bandwidths with 10-dB return loss are 12%, 20%,
60% and 25% for single element , two element array antenna ,
three element array antenna and four element array antenna
respectively at 3.5 Ghz. The single element antenna has very
less return loss at 3.4 Ghz so single element antenna should be
used at particular frequency. Two element array antenna has
highest bandwidth and highest radiation efficiency among
these four antenna and also has high directivity. The three
element array antenna has lowest bandwidth and low radiation
efficiency so it will be unmatched and high loss. Directivity
of four element antenna is highest but return loss is very high .
It is suitable where directivity is needed more. Among these
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