antenna design for automotive

1. Modified Sierpinski Fractal Circular Antenna for
Wireless Automotive Applications
A.MADHUSUDANAN
M.TECH SENSOR
SYSTEM TECHNLOGY
VIT UNIVERSITY,
VELLORE -632014.
a.madhusudanan2016@vit
student.ac.in
ANUPAMA SARKAR
M.TECH SENSOR
SYSTEM TECHNLOGY
VIT UNIVERSITY,
VELLORE -632014.
anupamasarkar2012@
gmail.com
S.PRABHAKARAN
M.TECH SENSOR
SYSTEM TECHNLOGY
VIT UNIVERSITY,
VELLORE -632014
prabhakaran.s2016@vit
student.ac.in
GUIDE:
DR. ELIZABETH RUFUS
PROFESSOR, SENSE
VIT UNIVERSITY,
VELLORE -632014
elizabethrufus@vit.ac.in
Abstract— In this paper, a novel structure of a planar monopole
antenna for wireless automotive applications is proposed. The
structure is based on the complementary Sierpinski triangle
surrounded by circular patch. The antenna has been modified
based on the iteration of triangles to improve the operating
bandwidth. The simulated results show good agreement with
the wideband characteristic. The proposed antenna was
designed to effectively support WLAN applications, at 2.4GHz.
The performance properties of the antenna such as return losses,
radiation patterns were verified by simulation
Key W0rds— SIERPINSKI, BANDWIDTH, WLAN.
I.)INTRODUCTION
In recent years, with widespread deployment of wireless
communications, especially in automotive vehicle to vehicle
communication, low cost, multiband antenna has increased
rapidly. WLAN are designed to operate in the 2.4GHz (2.4-
2.48GHz). The micro strip antenna has been widely analysed,
studied and developed. The micro strip antenna has the
characteristics of small size, light weight and low fabrication
cost. The fractals antennas are adopted for size reduction and
multiband/wideband characteristics. The size reduction is
mainly due to the self-similarity property of fractal geometry
and made of many copies of themselves with different scale
factors. The space filling characteristics of fractal antenna result
in increasing electrical length of the antenna. The
miniaturization effect of the fractal antenna is because of the
lengthening of the surface current line. The electrical length of
the antenna is increased and the structure can be miniaturized.
A lot of fractal geometries are available but only a limited
number are used in the design of micro strip antenna. One of
them is the Sierpinski Carpet geometry. The construction of
many ideal Fractal shapes is usually carried out by applying an
infinite number of times an iterative algorithm such as the
multiple reduction copy machine (MRCM) algorithm. In such
iterative procedure, an initial structure called generator is
replicated many times at different scales, positions and
directions, to grow the final Fractal structure. Fractal's antennas
are widely preferred for wireless communication systems as
they are of small size, light weight, low profile, low cost, and
are easy to fabricate and assemble.
The Sierpinski triangle geometry drew the attention of
researchers as it is smaller than other patch geometries .The
design of Sierpinski starts with a triangle with an operating
frequency in between 2.3GHz to 2.5 GHz at various iterations.
Two different iterations of triangular patch are compared in terms
of their return loss and bandwidths
.
II.)PROPOSED ANTENNA DESIGN
Classical Sierpinski triangle is having the scale factor of 2. This
is given by
δ =hn/hn+1 (1)
Where the n represent the iteration number and h represent the
height of the triangle. The antenna is fed by micro strip line, the
centre micro strip line (Lg×Wg) is having 50Ω impedance. It is
calculated using the equation (2) and (3).
∈ 𝑒𝑓𝑓 =
∈𝑟+1
2
+
∈𝑟+1
2
[
1
√1+12
ℎ
𝑤
] (2)
𝑍𝑜 = 𝑍𝑖𝑛 𝑐𝑜𝑠2
(
𝜋𝑑
𝐿𝑝
) (3)
Where Zo = 50 ohms and Zin = 1/G1
𝐺1 = {1/90 (
𝑤
λo
) 2
}
𝑤 ≪ λo
𝐺1 = {1/120 (
𝑤
λo
)
1
}
𝑤 ≫ λo
Where ∈ 𝑒𝑓𝑓 = 𝑒𝑓𝑓𝑒𝑐𝑡𝑖𝑣𝑒 𝑑𝑖𝑒𝑙𝑒𝑐𝑡𝑟𝑖𝑐 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡
∈ 𝑟 = 𝑑𝑖𝑒𝑙𝑐𝑡𝑟𝑖𝑐 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡 𝑜𝑓 𝑠𝑢𝑏𝑠𝑡𝑎𝑡𝑒
ℎ = ℎ𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑠𝑢𝑏𝑠𝑡𝑟𝑎𝑡𝑒
𝑤 = 𝑤𝑖𝑑𝑡ℎ 𝑜𝑓 𝑡ℎ𝑒 𝑝𝑎𝑡𝑐ℎ
𝑍𝑜 = 𝑜𝑢𝑡𝑝𝑢𝑡 𝑖𝑚𝑝𝑒𝑑𝑎𝑛𝑐𝑒
𝑍𝑖𝑛 = 𝑖𝑛𝑝𝑢𝑡 𝑖𝑚𝑝𝑒𝑑𝑎𝑛𝑐𝑒

2. 𝑑 = 𝑓𝑒𝑒𝑑 𝑝𝑜𝑖𝑛𝑡
𝐿𝑝 = 𝑙𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑡ℎ𝑒 𝑝𝑎𝑡𝑐ℎ
𝐺1 = 𝑒𝑓𝑓𝑒𝑐𝑡𝑖𝑣𝑒 𝑐𝑜𝑛𝑑𝑢𝑐𝑡𝑎𝑛𝑐𝑒
λo = resonating wavelength
A circular microstrip patch can be designed by using following
equation with specified information including dielectric
constant of substrate (∈ 𝑟), resonant frequency (fr) & height of
the substrate (h).
The radius (a) of circular micro strip patch is
Where
Here circular patch antenna has been designed and simulated at
2.4GHZ resonant frequency. The original gasket is constructed
by removing a central triangle from circle with radius 28 mm.
The third iteration of fractal antenna has been constructed by
inscribing the Triangle makes three copies and positioned so
that each triangle touches the Midpoint of each side of large
triangle as shown in fig1. Fifth iteration are achieved in this
manner shown in the Fig.2. This antenna has been fed with the
micro strip feed with feed point d=24.456mm. Alumina (96%)
loss free is used as substrate with dielectric constant εr = 9.4.
The length and width of the patch is taken to be 60mm & 48
mm respectively. The substrate height is selected to be 1.60
mm. The design specifications & physical dimensions are listed
in Table 1.
Table 1
Fig 1: proposed antenna design-third iteration
Fig 2: proposed antenna design-fifth iteration
III.) RESULTS & ANALYSIS
The return loss of antenna at 3rd
and 5th
iteration is shown in the
figure 3 and 4.The third iteration of the antenna having
bandwidth of 0.01GHZ with return loss is less than -12dB . The
fifth iteration of the antenna having bandwidth of 0.03GHZ with
return loss is less than -15dB return loss is less than -15dB which
show good impedance matching. The operating frequencies of
the antenna suitable for many wireless communication
applications such WiMAX (2.11–2.2), WLAN (2.4) GHz.
Fig 3: S parameter plot with return loss for antenna with 3rd
iteration

3. Fig 4: S parameter plot with return loss for antenna with 5th
iteration
The polar radiation patterns of antenna at third
iteration and fifth iteration is described in the Figure 5 and 6.
The main lobe direction and magnitude have been mention
under each plot. The polar radiation patterns of antenna at third
iteration show that at resonance frequency 2.4GHz, the main
lobe magnitude and direction have 0.561 dBi and 49 deg. The
3dB angular width which is also known as half power beam
width in the elevation plane has 61.6 deg. The half power beam
width is shown by two thin lines which show that when the
directivity increases the angle between the two lines decreases.
Antenna at fifth iteration with same resonance frequency shows
the main lobe magnitude and direction have 4.83 dBi and 22
respectively. The 3dB angular width which is also known as
half power beam width in the elevation plane has 116.5 deg.
Fig 5: polar plot for antenna with 3rd
iteration
Fig 6: polar plot for antenna with 5th
iteration
The 3-D radiation patterns of antenna at third iteration and fifth
iteration is shown in the Figure 7 and 8.The Directivity and Total
radiation efficiency have been mention under each plot. The 3-D
radiation patterns of antenna at third iteration show that at
resonance frequency 2.4GHz, the directivity and total radiation
efficiency have 4.833 dBi and-24.31 dB. Similarly radiation
patterns of antenna at fifth iteration show that at resonance
frequency 2.4GHz, the directivity and total radiation efficiency
have 6.309 dBi and -19.63 dB. Here the directivity of antenna
increases by increasing number of fractal structures in
iterations.so it can be used for high directional applications.
Fig 7: 3-D Radiation Pattern for antenna with 3rd
iteration
Fig 8: 3-D Radiation Pattern for antenna with 5th
Iteration

4. IV.) CONCLUSION
The present work has been carried out for the 3rd and 5th
iteration. From the above discussions it can be concluded that
on increasing the number of iterations the return loss and gain
of antenna are also increased. Also it can be concluded that the
self-similarity in the structure for the 3rd and 5th iteration to
possess shift in centre frequency, i.e., multiband. These
multiband antenna can cover the frequency bands of
WLAN/WIMAX applications. The designed antenna resonates
in (2.4- 2.6GHz) frequency band and can be used in Vehicle to
vehicle (V2V) and vehicle to infrastructure (V2I)
communications. With V2V communications, there are a large
number of signals being passed back and forth. The common
number is 1,000 to 1,500 received messages per second from
cars within a near proximity (roughly 100m). Table 2 shows the
comparative results of antenna for 3rd
and 5th
iterations.
S.NO Iteration Return
Loss
Gain VSWR Directivity
1.) Third
iteration
-11.63 - 3.550 1.723 4.833
2.) Fifth
iteration
-13.73 2.505 1.53 6.039
Table 2: Comparative Table of Modified Sierpinski Fractal
Circular Patch Antenna
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