International Conference on Electrical, Computer and Communication Engineering (ECCE), February 16-18, 2017, Cox’s Bazar, Bangladesh
A Compact Low-profile Ultra Wideband Antenna
for Biomedical Applications
Foez Ahmed,1,∗ Nisab Hasan,2 and Md. Halim Miah Chowdhury3
1,2,3
Department of Information and Communication Engineering
Faculty of Engineering, University of Rajshahi, Rajshahi-6205, Bangladesh
Email: ∗ foez.kku@gmail.com
Abstract—This paper presents a compact planar ultrawideband (UWB) microstrip antenna for microwave medical
applications. The proposed antenna has a low profile structure,
consisting of a modified radiating patch with stair steps and open
slots, microstrip feed line, and T-like shape slots at the ground
plane. The optimized antenna is capable of being operated in frequency range of 3.06–11.4 GHz band having good omnidirectional
radiation pattern and high gain, which satisfies the requirements
of UWB (3.1–10.6 GHz) applications. The antenna system has
a compact size of 18×30×0.8mm3 . These features make the
proposed UWB antenna a good candidate for microwave medical
imaging applications.
Index Terms—UWB Antenna, Microwave medical imaging,
Monopole, Planar, Miniaturization.
I. I NTRODUCTION
Fig. 1. Optimized geometry of the proposed UWB Antenna (Left Side:
Complete Antenna Structure, Right Side: Details of Patch and Ground Plane).
Since 2002, after the declaration of unlicensed spectrum
from 3.1 GHz to 10.6 GHz [1] for ultrawideband (UWB) applications, the microstrip UWB antennas have much attention
due to its various attracted applications. Among the UWB applications, UWB antennas for microwave medical applications
(e.g. breast tumor detection, brain tumor detection, health monitoring, cancer detection and so on) have considerable interest
in recent years owing to their numerous advantages such as
low cost, non-ionizing, low health risk, sensitive to tumors
and specific to malignancies, easy integration with monolithic
microwave integrated circuits (MMIC) and ease of fabrication.
However, one of the major challenges in antenna technology is
to design of ultra wideband compact omnidirectional antenna
with constant gain [2].
Over the decade, various antennas have been studied to
achieve UWB applications – particularly for medical imaging applications. A circular disc shaped metal antenna was
developed in [3]. The dimension of the proposed antenna
system is 40×40×0.5mm3 and it covers the frequency range
of 3.5–8 GHz only. In [4] the designed antenna, comprised
of rectangular patch with semicircular ground plane, has the
system size of 25×30×0.794mm3 and the frequency range of
3.55–11.17 GHz. However, it fails to cover the whole operating
band of UWB operations. A rectangular patch antenna with
partial ground plane presented in [5] has large system size of
34×36×1.58mm3 but showing the good coverage bandwidth
of 2.68 GHz to 12.06 GHz. A Bowtie patch antenna system
(36.5×40.5×0.8mm3 ) proposed in [6] covers the frequency
range of 4 GHz to 8 GHz. Besides these, there are few
other compact UWB antennas have been proposed recently.
Such as, in [7] a compact conventional patch antenna with
inverted L-strip (total system size of 25×25×1.6mm3 ) was
developed for ultra-wide band applications. In [8], the Ultrawideband antenna is designed for near-field imaging and the
total system size is 30×26×1.6mm3 . Another compact and
planar antenna with arch-shape strip developed in [9] has the
system size of 16×20×1.6mm3 . However, most of the reported
antenna systems have either higher substrate height or longer
dimensions. Even few of them are not able to cover the entire
bandwidth of UWB (3.1–10.6 GHz) operations.
Therefore, the goal of this paper is to design an antenna
with the UWB features that could be a good candidate for
microwave imaging system for medical applications. The
interest is to achieve increased bandwidth. The reduction in
size is also a consideration to be taken into account in the
design of this antenna.
II. A NTENNA C ONFIGURATION
The proposed optimized antenna geometry is shown in
Fig. 1 with dimensional details. The monopole antenna is
fed by a 50Ω microstrip line, which is printed on the FR4
Epoxy substrate with a total system size of SubW×SubL
= 18×30mm2 , thickness of 0.8mm and relative dielectric
constant of 4.4. The patch is connected to a microstrip feedline with the width of FW and length of FL. This design
is introduced to obtain ultra-wide band accompanied with
good impedance matching over the entire operating band. The
rectangular patch is the basis of the monopole radiator, which
has the dimensions of Lp×Wp=17×16mm2 and printed on the
top surface of the substrate. A partial modified ground plane is
used, which is printed on the bottom surface of the substrate.
Its length is GL and width is the same as substrate’s width.
c
978-1-5090-5627-9/17/$31.00 2017
IEEE
87
A T like shape slot is introduced in the middle of the
ground plane to excite higher order resonance as well as to
improve the impedance matching that results in bandwidth
enhancement. Multiple stair step slots are placed into two
lower sides of the patch. These stair step slots may further
enhance the impedance bandwidth of the proposed antenna
system. Finally, additional three slots into the patch may have
a significant effect on the performance of our antenna to cover
the entire UWB band (3.1–10.6 GHz) shown in Fig. 2 and
in Fig. 3 respectively. However, the proposed antenna system
is optimized and analyzed using commercial software Ansoft
HFSS [11]. All the Optimized Parameters and corresponding
values for the proposed Antenna are listed in Table I.
TABLE I
O PTIMIZED PARAMETERS & VALUES FOR THE PROPOSED A NTENNA
(U NIT:M ILLIMETERS )
Parameter
SubW
FL
Wp
GL2
GW1
GW4
PL
PL1
PW5
Value
18
12
16
0.5
0.5
1.4
1
11
11.5
Parameter
SubL
FW
GL
GL3
GW2
GW5
PW1
PW3
PL2
Value
30
2
11
3
1.75
5.5
1
0.5
0.5
Parameter
SubH
Lp
GL1
GL4
GW3
GW6
PW2
PW4
Value
0.8
17
1
1.5
3.25
7
1.5
13
Fig. 3.
VSWR of the proposed UWB Antenna.
Fig. 4. Different antenna geometry (a) Ordinary square monopole antenna,
(b) Antenna with the ground slot, (c) Antenna with ground slots and stair step
slots at patch, (d) The proposed antenna structure.
a multiple of quarter-wavelength [10]. Hence, here added
ground slots can create an additional higher order resonant
path at the frequency of 11.3 GHz (slot length is around λ/4)
but the level of S11 is above the –10dB due to impedance
mismatch. Moreover, the antenna with modified ground plane
and optimum stair steps (optimized by Ansoft HFSS) patch
have the significant effects over the entire band except at the
beginning of the UWB band. Further by adding additional
three slots into the patch, the proposed antenna can cover the
wide frequency range of 3.06–11.4 GHz shown in Fig. 5.
Fig. 2.
Reflection coefficient (S11) of the proposed UWB Antenna.
III. R ESULTS AND D ISCUSSION
In this section, the effects of diffracted patch and modified
ground plane have been studied. The different geometrical
arrangements of UWB antennas used for simulation studies by
Ansoft HFSS are shown in Fig. 4. The reflection coefficient
(S11 in dB) for Fig. 4(a) ordinary square monopole antenna,
Fig. 4(b) antenna with the ground slot, Fig. 4(c) Antenna with
ground slots and stair step slots at patch and Fig. 4(d) the
proposed antenna are plotted in Fig. 5.
It is clearly observed in Fig. 5 that the ordinary square
monopole patch can excite the fundamental resonant modes at
lower band which can cover the frequency range from 3.42–
6.2 GHz only. In fact, each slot acts as like as a resonator
at its resonance frequency and resonant slot length will be
Fig. 5. Reflection coefficient (S11) of various structures mentioned in Fig. 4
88
Fig. 8.
3D Radiation pattern of the proposed UWB Antenna at 5 GHz.
Fig. 6. VSWR for different values of PL1 (PL1=11mm is the nominal value);
other values are fixed as listed in table I.
Fig. 9. 2D radiation pattern of proposed UWB antenna at 5 GHz over the
three cutting plane.
Fig. 7. VSWR for different values of PW5 (PW5=11.5mm is the nominal
value); other values are fixed as listed in table I.
Fig. 10.
To illustrate the significant effects of additional slots at
patch, various lengths and widths of the slots have been studied
and results are plotted in Fig. 6 and Fig. 7 respectively.
In Fig. 6, it is observed that the bandwidth of the antenna
increases as PL1 increases from 9mm to 11mm and apparently
at PL1 = 11mm, the bandwidth at VSWR<2 is matched
perfectly to cover the entire band of UWB applications. In
Fig. 7, it is noticed that at PW5 = 11.5mm the bandwidth at
VSWR<2 is matched perfectly to cover the entire band of
UWB applications.
Realized Gain (in dBi) of the proposed UWB Antenna.
IV. C ONCLUSIONS
In this paper, a miniature microstrip antenna for microwave
medical applications is presented. The antenna satisfactorily
meets the requirements and has an UWB attitude. The simulation in HFSS software led to a reflection coefficient of –
10dB from 3.06 GHz to 11.4 GHz and showing sufficiently
high gain over the required ultra-wide band which provides
a good performance for the spectrum allocated to the UWB
microwave medical applications by the FCC commission.
The 3D and 2D radiation patterns at 5 GHz of the proposed
antenna are plotted in Fig. 8 and Fig. 9 respectively. It is
observed that the radiation pattern is almost as like as a dipole
antenna. It shows an omnidirectional radiation pattern which
is desirable in ultra-wide band applications.
ACKNOWLEDGMENT
The authors would like to thank the Key Laboratory of
Antenna for Wireless Communications, Department of
Information and Communication Engineering, University of
Rajshahi, Rajshahi-6205, for supporting all types of technical
as well as simulation facilities.
The simulated realized gain of the proposed antenna system
is plotted in Fig. 10. The graph indicates enough high gain with
moderate fluctuations over the entire operating band (3.1–10.6
GHz) of UWB applications.
89
R EFERENCES
[1] Federal Communications Commission (FCC), Revision of Part 15 of the
Commissions Rules Regarding Ultra-Wideband Transmission Systems,
First Report and Order, FCC 02-48, 2002.
[2] V. A. Shameena, S. Mridula, S. Jacob, C. K. Ananandan, K. Vasudevan
and P. Mohanan, “A Compact Modified Ground CPW Fed Antenna for
UWB Applications,” Microwave Review, Vol. 17, No. 1, pp. 13-19, 2011.
[3] S. Adnan, R. A. Abd-Alhameed, C. H. See, H. I. Hraga, I.T.E. Elfergani,
and D. Zhou “A Compact UWB Antenna Design for breast Cancer
Detection,” PIERS Online, Vol.6, No.2, 2010.
[4] S. M. Chouiti, L. Merad and S. M. Meriah, “A Microwave Imaging
Technique Implementation for Early Detection of Breast Tumors,” Advances in Circuits, Systems, Signal Processing and Telecommunications,
Laboratory of Telecommunications of Tlemcen (LTT), University of
Tlemcen, Algeria.
[5] R. Karli, H. Ammor, J. E. Aoufi, “Miniaturized UWB Microstrip Antenna
for Microwave Imaging,” WSEAS Transactions on Information Science
and Applications, Vol. 11, 2014.
[6] W. Wasusathien, S. Santalunai, T. Thosdeekoraphat, C. Thongsopa, “Ultra
Wideband Breast Cancer detection by Using SAR for Indication the
Tumor Location,” International Journal of Medical, Health, Biomedical,
Bioengineering and Pharmaceutical Engineering, Vol. 8, No. 7, 2014.
[7] A. K. Gautam, S. Yadav and B. K. Kanaujia, “A CPW-Fed Compact UWB
Microstrip Antenna,” IEEE Antennas and Wireless Propagation Lett., Vol.
12, 2013.
[8] H. M. Jafari, M. J. Deen, S. Hranilovic and N. K. Nikolova, “A Study
of Ultra-wideband Antennas for Near-Field Imaging,” IEEE Transactions
on Antennas and Propagation, Vol. 55, No. 4, 2007.
[9] M. N. Shakib, M. Moghavvemi, and W. N. L. Mahadi, “Design of a
Compact Planar Antenna for Ultra-wideband Operation,” ACES JOURNAL, Vol. 30, No. 2, 2015.
[10] A. Foudazi, H. R. Hassani, and S. M. A. Neshad, “Small UWB
planar monopole antenna with added GPS/GSM/WLAN bands,” IEEE
Transactions on Antennas and Propagation, Vol. 60, pp. 2987–2992,
2012.
[11] HFSS v.15, Ansoft Corporation, Pittsburgh, PA, USA.
90