2019 IEEE Pune Section International Conference (PuneCon)
MIT World Peace University, Pune, India. Dec 18-20, 2019
Hexagonal Slotted Wearable Microstrip Patch
Antenna for Body Area Network
Mandar P. Joshi
Dept. of E & TC
GES’s R. H. Sapat CoE, M S & R
Nashik, India
mandarjoshi11@gmail.com
Jayant G. Joshi
Dept. of E & TC
Government Polytechnic
Nashik, India
jgjoshiantenna@gmail.com
Shyam S. Pattnaik
National Institute of Technical
Teachers’ Training and Research
Chandigarh, India
profshyampattnaik@gmail.com
using flexible foam substrate for wearable BAN application.
The proposed design of antenna exhibits circular polarized
characteristics with high gain more than 9 dBi. The antenna
also offers features like low profile, conformal and light
weight and low cost.
Abstract—This paper presents design of slot cut hexagonal
microstrip patch antenna for body area network application.
The antenna is resonating at 2.45 GHz with impedance
bandwidth of 70 MHz with gain of 9.14 dBi. The hexagonal
microstrip patch antenna is diagonally fed and a slot is etched
inside radiating patch to realize circular polarization (CP). The
antenna exhibits 20 MHz of axial ratio bandwidth. The overall
size of antenna is 80 × 80 mm2. The parametric analysis of slot
length has been carried out to determine length of slot. The
proposed antenna is fabricated using inexpensive flexible foam
substrate and measured results are found to be in close
agreement with simulated results.
II.
ANTENNA DESIGN
Keywords—Slot, polyethylene, BAN, wearable, circular
polarization
I.
INTRODUCTION
The growth in wireless communication applications leads
handheld communication devices. These devices need to be
compact, low profile and low weight. In present day, health
monitoring devices are gaining much popularity.
Technological developments in wearable and flexible
electronics communication systems helps to transmit and
receive signals in various body worn applications. These
applications demand a flexible, low profile, low weight
antennas with high gain characteristics. Microstrip patch
antennas (MPA) are adopted in such application as they are
low profile, conformal and can be fabricated using flexible
substrates. Antennas used for body area network application
are mounted either on human body or integrated with clothes
[1-8]. In literature, various wearable antennas for on-body
and off-body, body area networks (BAN) and other wireless
applications are presented. A compact low- profile vinyl
polymer based flexible triangular microstrip antenna using
Koch fractal geometry is reported [1]. A meandered line
antenna on flexible substrate [2], U slot loaded truncated
corner rectangular antenna on foam substrate [3] has been
reported. Application of split ring resonators as metamaterial
in wearable antennas for wireless applications is presented
using geotextile substrate for ‘T’ shaped microstrip patch
antenna [4], polyester based wearable microstrip antenna
with inter-digital capacitor [5] and metamaterial embedded
wearable microstrip antenna on flexible polyester substrate
has been fabricated and tested [6]. Circularly polarized (CP)
antenna can found advantageous for body worn applications
as transmitter and receiver antennas may not be perfectly
aligned. In this paper, a slot cut diagonally fed circularly
polarized hexagonal microstrip patch antenna is proposed
978-1-7281-1924-3/19/$31.00 ©2019 IEEE
(a)
(b)
Fig. 1. (a) Geometry of antenna (b) side view
Fig. 1(a) depicts geometry of proposed antenna design.
The hexagonal patch is designed to resonate at fundamental
mode TM10 having resonance frequency at 2.45 GHz. The
side length S is calculated by equating the hexagonal shape
with circular microstrip patch using equation (1) [7].
fr
k mnc
2S a e
Hr
(1)
where, kmn = 1.84118, c = 3 × 108 m/s, εr is relative
permittivity of substrate and ae is effective radius of circular
microstrip antenna. The determined side length S of
hexagonal microstrip radiator patch is 36 mm. The slot
having length and width of 8 mm and 3 mm respectively is
cut inside the hexagonal patch. The antenna is diagonally fed
using coaxial probe feed at x0 =10 mm and y0 = 10 mm. The
standard SMA connector having 0.12 mm center conductor
diameter is used fed the proposed antenna. The low- cost
polyethylene foam substrate having h = 1mm and εr = 1.07 is
used in designing and fabricating proposed antenna. Altair’s
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To optimize the slot dimensions, detailed parametric
analysis has been carried out. The length of the slot is varied
by protecting slot width constant and width of slot has been
varied considering constant length. It is observed that,
variation in slot width does not alters the performance of
proposed antenna. However, variation in slot length ‘l’
significantly affects the performance of antenna. This is
because the length of slot changes the electrical length of
current. Fig. 4 (a) and (b), represents the performance of
return loss and axial ratio characteristics for variation in
length respectively. As illustrated in Fig. 4, it has been
observed that, variation in length changes the impedance
bandwidth (S11 < -10 dB) of proposed antenna. However, it
also varies the axial ratio significantly. For increase in length
of slot, the axial ratio value become greater than 3. For l =7
mm, it is observed that the axial ratio bandwidth shifts
towards higher side. Therefore, an optimum value of l= 8
mm has been selected as slot length.
CAD FEKO is used to simulate the designed antenna [9].
Infinite ground plane is used to perform the simulations. An
adhesive copper tape [4-6] is used as a radiating element and
ground plane on both sides of foam substrate as presented in
Fig. 1(b). The adhesive copper tape is fine cut according to
the geometry of proposed antenna and then diagonally feed
to realize circular polarized response. The fabricated antenna
is tested using Anritsu MS2024B VNA and the measured S11
results are found to be in good agreement with the simulated
results.
III.
RESULTS AND DISCUSSION
The return loss (S11) characteristics of the diagonally fed
center slot cut hexagonal microstrip patch antenna (HMPA)
with foam substrate is presented in Fig. 2.
Fig. 2. Return loss characteristics of HMPA
The slot of appropriate length and width when cut inside
radiating patch, de-generates fundamental mode into two degenerating modes to realize circular polarized response as
depicted in Fig. 2. The proposed antenna exhibits simulated
bandwidth of 70 MHz at center frequency of 2.45 GHz. The
proposed antenna covers body area network band of 2.45
GHz. The axial ratio characteristics is presented in Fig. 3 The
antenna realized 20 MHz of axial ratio bandwidth for BAN.
(a)
(b)
Fig. 4. Variation in slot length (a) return loss (b) axial ratio
The surface current distribution for center frequency of
2.45 GHz is presented in Fig. 5 (a)-(d). The surface current is
rotating in anti -clockwise directions, realizing right hand
circular polarization (RHCP).
Fig. 3. Axial ratio characteristics of HMPA
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(a)
(b)
Fig. 8. Photograph of Fabricated prototype
(c)
(d)
Fig. 5. Surface current (a) 00 (b) 900 (c) 1800 and (d) 2700
Fig. 6 presents radiation pattern of proposed antenna. The
realized peak gain is of about 9.14 dBi. The radiation is in
broadside directions with RHCP. Stable gain characteristics
has been observed over entire axial ratio bandwidth and
depicted in Fig. 7.
Fig. 9. Simulated and measured return loss
Fig. 8 depicts fabricated prototype of proposed antenna
and in Fig. 9 simulated and measured S11 results are
compared and presented. Fig. 10 presents measured results
with experimental setup in inset.
Fig. 6. Simulated Radiation pattern at 2.45 GHz
Fig. 10. Measured result with experimental setup in inset
It is observed that, measured impedance bandwidth is
higher than simulated bandwidth because variations in
handmade fabrication process. The obtained results are
compared with some of previously reported results and
presented in table 1.
Fig. 7. Gain and axial ratio over frequency
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TABLE I.
COMPARISON WITH PREVIOUSLY REPORTED WEARABLE
ANTENNAS
Ref. No.,
Year
h
(mm)
εr
[1] 2019
0.508
[8] 2017
Propose
Size in
mm2
Impedanc
e BW (%)
Axial
Ratio
BW (%)
2.20
39 × 39
7.75
NA
2.06
4
1.2
60 × 60
9.46
NA
4.27
1
1.07
80 × 80
8.40
0.8
9.14
[2]
Gain
(dBi)
[3]
[4]
d Work
*NA – Not applicable, BW = Bandwidth
IV.
[5]
CONCLUSION
This paper presents, foam based flexible slot cut
hexagonal microstrip patch antenna. The proposed antenna
offers 2.85 % of impedance bandwidth and 0.8 % axial ratio
bandwidth. The measured impedance bandwidth is of about
8.40 % compared to simulated results. Antenna has stable
and broadside radiation pattern with maximum gain of 9.14
dBi. The projected antenna exhibits right hand circular
polarization. The measured S11 results are found in good
agreement with simulated results.
[6]
[7]
[8]
REFERENCES
[1]
A. Arif, M. Zubair, M. Ali, M. U. Khan and M. Q. Mehmood, “A
Compact Low-Profile Fractal Antenna for Wearable On-Body
[9]
WBAN Applications,” IEEE Antennas and Wireless Propagation
Letters, Vol. 18, No. 5, pp. 981-985, 2019.
M. Wagih, Y. Wei and S. Beeby, “Flexible 2.4 GHz Node for Body
Area Networks with a Compact High Gain Planar Antenna,” IEEE
Antennas and Wireless Propagation Letters, Vol. 18, No. 1, pp. 49-53,
2019.
Sapna Verma, Jamshed Aslam Ansari, “Analysis of U-slot Loaded
Truncated Corner Rectangular Microstrip Patch Antenna for
Broadband Operation,” International Journal of Electronics and
Communications (AEU), 2015.
J. G. Joshi, Shyam S. Pattnaik and S. Devi, “Geo-Textile Based
Metamaterial Loaded Wearable Microstrip Patch Antenna,”
International Journal of Microwave and Optical Technology, Vol.8,
No.1, pp. 25-33, 2013.
J. G. Joshi and Shyam S. Pattnaik, “Polyester Based Wearable
Microstrip Patch Antenna,” IEEE Applied Electromagnetic
Conference, 2013. DOI: 10.1109/AEMC.2013.7045103.
J. G. Joshi, Shyam S. Pattnaik and S, Devi, “Metamaterial Embedded
Wearable Rectangular Microstrip Patch Antenna,” International
Journal of Antennas and Propagation, Hindawi, Vol. 2012, Article ID
974315, DOI: 10.1155/2012/974315.
K. P. Ray and M. D. Pandey and S. Krishnan, “Determination of
Resonance Frequency of Hexagonal and Half Hexagonal Microstrip
Antennas,” Microwave and Optical Technology Letters, Vol.49,
No.11, pp. 2876- 2879, 2007.
Guo-Ping Gao, Bin Hu, Xiao-Long Tian, Qing-Lin Zhao and BingTao Zhang, “Experimental Study of Wearable Aperture Coupled
Patch Antenna for Wireless Body Area Netwrok,” Microwave and
Optical Technology Letters, Vol. 59, No. 4, pp. 761- 766, 2017
Altair’s Hyperworks CAD FEKO, Altair Engineering Inc. USA
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