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Design and Simulation of Single patch and Linear
Array (1x3) for Smart Antenna Applications V.S. Prabhu, R. Archana, A.M. Fiearlin Mercy, G. Bhavya Sree,
Assistant Professor, Dept of ECE, Dept of ECE, Dept of ECE,
Dept. of ECE, R.M.D. Engg.College, R.M.D.Engg. College, R.M.D. Engg. College,
R.M.D. Engg. College, Thiruvallur, India. Thiruvallur, India Thiruvallur, India.
Thiruvallur, India
Abstract—The design of smart antenna for cellular networks
can be implemented with single microstrip patch antenna.
But in some cases the radiation pattern, gain and directivity
requirement for certain applications were unable to meet by
the single element antenna. Suitable solutions can be
obtained by combining more than one antenna which is
generally called as the antenna array. In this paper, a
microstripsingle patch antenna and a linear microstrip patch
antenna array of (1x3) was designed and simulated to meet
tripleISM frequency band of 2.45GHz, 4.5GHz and 7.1GHz.
Thus due to this multiband frequencies the smart antenna
designed can be used for multiple applications. The return
loss obtained in S11 plot is -35 dB at 4.5GHz and 7.9GHz for
single patch antenna and linear array antenna respectively.
The microstrip patch and linear antenna array was designed
and simulated in ADS software. The radiation pattern
obtained was found to be narrow and thus can be
implemented for smart antenna applications.
Keywords-- linear array, microstrip patch antenna, ISM
band.
I. INTRODUCTION
The development recently made in the field of antenna has
lead to the need of high gain, narrow band radiation pattern
and directivity. Usually the radiation pattern of a single
element is relatively wide, and each element provides low
values of directivity and gain. In many applications it is
necessary to design antennas with very high directive
characteristics to meet the demand of long distance
communication. This can be accomplished by multi-elements
which is referred to as arrays [1]. The antenna arrays can be of
any forms like linear, circular, rectangular, spherical, etc. The
design and simulation of microstrip patch and a linear array of
(1x3) was done in this paper.
The arrays are equally spaced and are placed in a straight
line for linear arrays.However, if some of the manifold vectors
are linearlydependent, then the ambiguity problem is said to
arise,implying a need to identify array geometries that are free
ofsome type of ambiguities, as well as estimating the set
ofambiguous directions associated with a given geometry
[3].The main problem in designing the antenna array was
instrumental in selecting elements which conform to the
geometry of the device, and an array architecture that could
control the radiation pattern in both the azimuth and elevation
directions [4].
The preliminary design was to select the dimensions of the
rectangular patch. And for the antenna array the preliminary
design resulted in the selection of microstrip patches,
arranged in a linear array configuration. In addition, the
number of radiating elements was chosen to meet beam width
requirements. Mutual-coupling effects between the antenna
elements were also considered, as they affect the overall
performance of the antenna array. Mutual couplingresults in
radiation patterns that have shallower and shifted nulls,
and less accurate angles of arrival, thus causing a
deterioration in the overall performance of antenna system.
Figure 1. Rectangular microstrip antenna element
The antenna array is designed from the rectangular
microstrip patch antenna. The design of single patch antenna
was discussed in section 1. Microstrip patch antenna consists
of a radiating patch on one side of a dielectric substrate with
acontinuous metal layer bonded to the opposite side of the
substrate which forms a ground plane.The patch is generally
made of conducting material such as copper or gold and can
take anypossible shape. [5]. The major advantages of selecting
microstrip patches are very low cost, reduction in weight,
planar or conformal and ability of integration with electronic
or signal processing circuitry. Microstrip antenna array
consists of microstrip antenna elements, feed and phasing
networks. Designing microstrip structure requires
understanding of both mathematical relatives and its
application [6].
In most microstrip end fed antennas the feed line
impedance (50) is always the sameas the radiation resistance
at the edge of the patch, which is usually a few hundred
ohmsdepending on the patch dimensions and the substrate
used. As a result this inputmismatch will affect the antenna
performance because maximum power is not beingtransferred.
When a matching network is implemented on the feed network
thisimproves the performance of the antenna as there are less
reflections [7]. A typical method used to match the antenna is
the use of an inset feed, because theresistance varies as a
cosine squared function along the length of the patch a 50
can befound which is a distance from the edge of the patch
[8].The emphasis on theoretical and practical design
techniques of available substrate materials are reviewed along
with the relation between dielectric constant tolerance and
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resonant frequency of microstrip patches [9]. Practical procedures are given for standard rectangular patches, as wellas variations on those designs are summarized [10].The design of linear microstrip array is explained in section 3.
II.SINGLE PATCH ANTENNA DESIGN
The microstrip patch antenna was designed in ADS
software. Microstrip patch antenna is made up of two sides.
One side is the ground plane and the other side is the radiating
patch with a continuous metal layer. The patch is made up of
gold or copper and it can take any shape.
The design equations of the single patch are given below.It
was considered that the relative permittivity, r =8 and height
h=0.15 cm.
The width of microstrip patch antenna is given by the
equation (1),
1
2
2
rr
o
f
vW
(1)
W= 2.946 for 2.45GHz ; 1.57 for 4.5 GHz ; 0.995 for 7.1 GHz
The Effective relative dielectric permittivity is given by
the equation (2),
2/1
1212
1
2
1
W
hrrreff
(2)
reff =7.257 for 2.45 GHz; 6.88 for 4.5GHz ; 6.588 for
7.1GHz
The change in length is given by the equation (3),
8.0258.0
264.03.0
412.0
h
W
h
W
hL
reff
reff
(3)
L = 0.06 for 2.45GHz ;0.06 for 4.5GHz; 0.06 for 7.1GHz
The actual length of the Patch is given by the equation (4),
𝐿 = Lf ooreffr
22
1
(4)
L= 2.15cm for 2.45GHz ;1.15cm for 4.5GHz ; 0.703cm for
7.1GHz
The effective Length of the Patch is given by the
equation(5),
ef fL = LL 2 (5)
ef fL = 2.27cm for 2.45GHz ;1.27 for 4.5GHz ; 0.823 for
7.1GHz
A method used to match the microstrip patch antenna is by
an inset feed. In the inset feed the resistance varies as a cosine
squared function along the length of the patch. The input
resistance of the inset feed is found by the formula given
below.
Rin = 1
2 𝐺1±𝐺12 𝑐𝑜𝑠2(
∏
𝐿𝑦𝑜) (6)
yois the depth of the inset feed into the rectangular patch.
Generally yois taken as half the total length of the rectangular
patch.
Where G1 is the conductance of slot 1 and G12 is the mutual
conductance between slot 1 and 2 of the microstrip antenna.
𝐺1 =
𝑊2
90 х 𝜆2 𝑓𝑜𝑟𝑊 ≪ 𝜆
𝑊2
120 х 𝜆2 𝑓𝑜𝑟𝑊 ≫ 𝜆
(7)
The dielectric substrate of appropriate tangential loss and
thickness „h‟must be selected. Substrates of high thickness are
mechanically strong, and it will increase the radiated power,
reduceconductor loss and improve the impedance
bandwidth.A high loss tangent increases thedielectric loss and
therefore reduces antenna efficiency.
Figure 2.Single Patch Antenna Model and design in ADS
For the calculated design parameters, antenna design is
proceeded with ADS Software. After creating a new project,
the initialization steps like grid spacing, and layout units are
defined. Here the substrate is selected as 60 mil thick and loss
tangent of 0.002 for the operating frequency of 2.4GHz. Patch
width has a minor effect on the resonant frequency and
radiation pattern of the antenna.With the proper excitation, a
patch width „W‟ is obtained which is greater than the patch
length „L‟, without excitingundesired modes. In this paper, a
broadband rectangular microstrip patch antenna is designed
using the permittivity r of 3.4 and log tan δ of 0.002. The
width and height of the patch is 30mm and 34mm
respectively. The single patch antenna designed in the ADS
software with its feeding structure, by means of a microstrip
line was shown in the Fig. 2.The width and height of
microstrip line is 3.5mm and 31mm respectively.
The loss in the signal power due to the reflections caused at
a discontinuity in a transmission line is generally called the
return loss. The return loss plot for the designed single patch
antenna was shown in fig 3.
Directivity is a measure of isotropic antenna. The gain of
the antenna directly dependson the radiation efficiency and the
directivity of the antenna.
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Figure 3: Return loss plot for single patch antenna
From the figure 3, the return loss of -6dB, -35dB and –13
dB occurs at 2.4GHz, 4.4GHz and 7.2GHz respectively.
Normally, while supplying power to the antenna, reflection of
power takes place. For better efficiency, this reflected power
should be as low as possible. The „0‟ dB in the graph shows
that 100% of the power is reflected. As it goes on decreasing,
it clearly indicates that there is minimum reflection of power.
The S11 plot in the figure3 shows, minimum amount of power
is reflected in the above mentioned frequencies.
It is observed that directivityincreases with increase of
substrate thickness and patch width. Conversely, the
beamwidth isexpected to decrease for higher values of „h „and
„W‟. The simulation of the antenna model was done in ADS
software by the pre-processing step. By computing the far
field, antenna parameters such as gain, directivity, effective
angle are calculated. High directivity shows that antenna is
directed in the direction of strongest emission. And by the
post-processing step, the three dimensional view and the
animated view of radiation pattern is obtained.
III. LINEAR ANTENNA ARRAY
The 1x3 linear patch antenna was designed by connecting
three single patch antennas to the matching circuits.The height
and width of the single patches in the linear array antenna
were similar as that of single patch antenna discussed in the
section1.The matching circuit for the array is developed in the
schematic window of ADS and then produced to the layout
window. The uniform linear array of patches with spacing of
λ/2 is arranged as shown in figure 3.
Figure 4. 1x3 linear patch antenna designed in ADS
Figure 5: Return loss plot for linear antenna array
The S11 plot in the figure 5 shows, minimum amount of power
is reflected in the frequencies 2.6GHz, 5.0 GHz and
7.9GHz.When an antenna is connected by a feed line,
the impedance of the antenna and feed line must match exactly
for maximum energy transfer from the feed line to the antenna
to be possible.Return loss is the loss of signal power resulting
from the reflection caused at a discontinuity in a transmission
line.From the fig 5, it is clearly shown that the return loss lies
around -20dB for the linear array antenna. Thus the designed
linear array has high resistance to reflection.
IV. RESULTS AND DISCUSSIONS
The most important characteristics of the antenna array
include the radiation pattern. The radiation pattern implies the
gain, directivity and the beamwidth. Radiation pattern is
computed using method of moments in ADS. The radiation
pattern for the single patch and uniform linear antenna array
for the three frequencies are shown in below Figures. Also by
the post processing step the animated view of radiation
patterns are obtained shown in fig 9 and fig 13.
The radiation pattern plays a vital role in antenna array. It
is observed that the radiation pattern of the linear array is
found to be narrow and thus useful in various smart antenna
applications. The gain of the antenna is the quality which
describes the performance of the antenna to concentrate
energy through the direction to to give a better picture of the
radiation performance.The below tabulation shows the antenna
parameters like Directivity, Gain, Power radiated for the three
different frequency ranges.
Operating
frequency
Directivity Gain Power radiated
Single
patch
Linear
array
Single
patch
Linear
array
Single
patch
Linear
array
2.4 GHz to
2.6GHz
5.434
9.547
3.089
6.553
0.582
0.501
4.4 GHz to
5 GHz
7.074
11.552
6.697
7.817
0.917
0.423
7 GHz to 8
GHz
8.557
11.492
6.935
9.808
0.688
0.678
Table1 Performance comparision of single patch & linear array antenna
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Figure 6: Radiation pattern of single patch antenna at 2.4 GHz
Figure 7: Radiation pattern of single patch antenna at 4.4 GHz
Figure 8: Radiation pattern of single patch antenna at 7.4 GHz
Figure 9: Animated view of single patch antenna
Figure 10: Radiation pattern of 1x3 antenna array at 2.6 GHz
Figure 11: Radiation pattern of 1x3 antenna array at 4.9 GHz
Figure 12: Radiation pattern of 1x3 antenna array at 8 GHz
Figure 13: Animated view of Linear array antenna
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VI. CONCLUSION
The antenna array designed with linear microstrip patch antenna provides narrow radiation pattern and have better directivity compared to that of single patch microstrip antenna.The designed linear antenna array has high resistance to reflection. The reason that patch antenna arrays are employed for wireless applications are due to their high gain even at their low profiles as inferred from the above tabulation. Due to better antenna parameters, narrow beamwidth and multiple operating frequencies, linear array antenna can be used for applications like Bluetooth at 2.4 GHz, Mobile Wi-Fi at 2.45 GHz and C - Band applications which includes commercial Wi-Fi , Satellite communications, Broadcasting etc in the range of 4 to 8 GHz.From the results obtained it is concluded that the linear array can be used in smart antenna system with triple band applications. This triple band frequency applications are used for cellular networks particularly in adhoc networks as it gives a satisfactory performance.
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