IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 53, NO. 9, SEPTEMBER 20053067
Wide-Band Modified Printed Bow-Tie Antenna With
Single and Dual Polarization for C– and X-Band
Abdelnasser A. Eldek, Member, IEEE, Atef Z. Elsherbeni, Senior Member, IEEE, and
Charles E. Smith, Life Senior Member, IEEE
Abstract—A modified printed bow-tie antenna is designed to si-
12.5 GHz. The presented antenna has an end fire radiation pattern
that makes it suitable for integration in single and dual polarized
phased array systems. The antenna exhibits small size and wide
bandwidth of 91%. The radiation characteristics are presented for
a single element and a linear array of this antenna.
Index Terms—Bow-tie, dual polarization, phased arrays, radar,
hibit a low profile, small size, light weight, low cost, high ef-
ficiency, and ease of fabrication and installation. Furthermore,
they are readily adaptable to hybrid and monolithic microwave
integrated circuits’ fabrication techniques at RF and microwave
Communication and phased array systems that operate in the
C and X-bands are normally designed using separate antennas
for each band. Since it is becoming more and more important
to use such systems in one setting, it is desirable to design a
single antenna that operates in both frequency bands. This, in
turn, requires a wideband antenna that covers the two bands.
In addition, many applications require end fire patterns, which
can be produced by different types of antenna elements. Among
the most widely used printed antennas in phased array systems
are the quasi-Yagi antenna –, dipole antenna –, and
printed bow-tie antenna –. The quasi-Yagi provides up
to 48% bandwidth –. The microstrip-fed dipole provides
2:1 VSWR of 19%, 50%, 56%, and 40% impedance bandwidth
in – and , respectively, and 1.5:1 VSWR of 30% in
sented in – provide up to 50% bandwidth. Recently, the
authors showed that replacing the dipole and the director of the
RINTED microstrip antennas are widely used in wireless
communication and phased array applications. They ex-
Manuscript received September 27, 2004; revised November 24, 2004.
A. A. Eldek was with the Center of Applied Electromagnetic Systems Re-
search (CAESR), Department of Electrical Engineering,The Universityof Mis-
sissippi, University, MS 38677 USA. He is now with the Department of Com-
puter Engineering, Jackson State University, Jackson, MS 39217 USA.
A. Z. Elsherbeni and C. E. Smith are with the Center of Applied Electro-
magnetic Systems Research (CAESR), Department of Electrical Engineering,
The University of Mississippi, University, MS 38677 USA (e-mail: atef@ole-
Digital Object Identifier 10.1109/TAP.2005.851870
proves the bandwidth (60%), size, and radiation characteristics
of the antenna . Further research by the authors resulted in
a novel coplanar waveguide fed slot and microstrip fed printed
antennas, which are called slot and printed Lotus antennas .
The printed Lotus provides 57% bandwidth relative to
and 60% relative to
. The presented antennas, however,
is the objective of this paper.
This paper presents a modified printed bow-tie antenna that
exhibits a wide bandwidth (BW). The return loss, and far field
radiation characteristics of this antenna are presented. In addi-
tion, two array configurations are presented to improve the pat-
tern stability across the operating bandwidth. The simulation
and analysis for the presented antennas are performed using the
commercial computer software package, Ansoft HFSS, which
is based on the finite element method. Measurements of return
loss, and radiation patterns are also conducted for verification
of these new antenna designs.
II. SINGLE ELEMENT MODIFIED BOW-TIE
The proposed antenna is printed on a Rogers RT/Duroid
6010/6010 LM substrate of a dielectric constant of 10.2, a
of 0.0023 and a thickness of 50 mil (1.27
mm). The geometry, parameters, and top and bottom views for
a prototype of the proposed antenna are shown in Fig. 1. The
antenna consists of two identical printed bows, one on the top
and one on the bottom of the substrate material. The top and
bottom bows are connected to the microstrip feedline and the
ground plane through a stub and mitered transition to match
the bow-tie with the 50
feedline, as illustrated in Fig. 1. The
antenna dimensional parameters, shown in Fig. 1, Wf, W1, W2,
W3, W4, W5, Lf, L1, L3, L3. L4, L5, L6, and L7 are 1.2, 1.52,
0.45, 0.62, 2, 2.49, 10, 5.34, 0.45, 0.68, 0.24, 2.61, 5.56, and
9.68 mm, respectively. The substrate size (width
may occur because of the effect of the SMA connector and fab-
rication imperfections. Both the simulation and measurements
show that the antenna operates over a wide range that extends
from 5.3 GHz to more than 14.2 GHz, with an impedance band-
width of approximately 91%.
0018-926X/$20.00 © 2005 IEEE
3068 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 53, NO. 9, SEPTEMBER 2005
Fig. 1.Antenna geometry, parameters, and prototype.
Fig. 2. Measured and computed return loss for the modified bow-tie antenna.
Compared to the conventional bow-tie antenna, this antenna
has a much wider bandwidth, which may result from two prop-
decreases the reflections from the sudden truncation of the tri-
angular bow-tie shape. Second, it has a well-designed matching
circuit that matches the bow-tie with the microstrip feed line.
The measured and computed radiation patterns at the oper-
atingband centerfrequency,9GHz,are showninFig.3.Agood
agreement is noticed, which further verifies the simulation re-
sults using Ansoft HFSS. The radiation patterns are then com-
puted at selective frequencies that cover almost the entire oper-
ating band, and shown in Fig. 4 at 6, 8, 10, and 12 GHz. The
properties of these patterns are summarized in Table I. Good ra-
diation characteristics are obtained up to 10 GHz. The radiation
pattern starts to deteriorate at 12 GHz. For the frequencies less
than 12 GHz, the antenna has wide beamwidth that ranges from
95 to 150 in the E-plane and from 115 to 180 in the H-plane.
It has a maximum cross polarization level of
ratio (F-to-B) of 12 dB. The antenna gain has an average value
of 6 dB. According to these results, the operating bandwidth
the (a) E-plane and (b) H-plane, for the modified bow-tie antenna at 9 GHz.
Comparison between the measured and computed radiation patterns in
of the antenna, as a single element, is between 5.3 and 10 GHz,
whichis around 61.4%. However, unconventional configuration
of this antenna can further improve the radiation characteristics
at higher frequencies in array environments.
III. TWO-ELEMENT ARRAYS
The coupling between array elements is an important param-
eter in phased array performance, because high coupling re-
sults in scan blindness and anomalies within the desired band-
width and scan volume. Therefore, a two-element array is de-
signed to examine the coupling between elements. In addition,
another configuration of two-element array is designed to im-
prove the pattern stability above 10 GHz. The two configura-
tions are shown in Fig. 5. Array 1 consists of two identical el-
ements, while the second element in Array 2 is mirrored along
the y-axis, and consequently a 180 phase shift is introduced
at port 2 in order to force the surface currents in the two ele-
ments to be in the same direction. This modification in Array
2 provides balanced patterns at high frequencies, where the ef-
fect of the substrate height is significant. In order to reduce the
ELDEK et al.: WIDE-BAND MODIFIED PRINTED BOW-TIE ANTENNA 3069
Fig. 4. Computed radiation patterns at 6, 8, 10, and 12 GHz.
FAR FIELD RADIATION PROPERTIES
Fig. 5. Two-element array configurations. (a) Array 1. (b) Array 2.
is chosen to be 14 mm, which is around
quency of the X-band.
Array 1 is fabricated, and its measured and computed S21 are
shown in Fig. 6. The average coupling is around
entire operating band. A comparison between the two arrays is
performed in terms of S-parameters as shown Fig. 7, and radia-
tion patterns at 6, 8, 10, 12, and 14 GHz as shown in Fig. 8. S11
and S22 of Array 2 are identical because of the array symmetry.
While no significant difference is noticed in the return losses
and coupling, notable improvement in the radiation patterns is
obtained by using Array 2. These improvements include much
at the upper fre-
Fig. 6.Array 1. (a) Prototype. (b) Measured and computed S21.
Fig. 7.Computed (a) return loss. (b) Coupling, for Array 1 and Array 2.
lower cross polarization levels, wider beamwidth, symmetrical
patterns around the y-axis, and wider usable bandwidth that in-
cludes 14 GHz. Hence, Array 2 is expected to perform better as
an element in a large phased array system.
Two four-element arrays of the modified bow-tie antenna are
fabricated (based on Array 2 configuration shown in Fig. 5),
with feeding networks for 0 and 10
measurement of the radiation pattern from these two array
configurations are presented in the Fig. 9 along with the HFSS
simulation results at 9 GHz. A 180 phase shift is introduced
by increasing the length of the feedlines of the second and
fourth elements by
steer the main beam from 90 to 80 , progressive phase shift,
, is added by increasing the feed length by 0,
0.8, 1.6, and 2.4 mm for the elements counted from left to
right 1, 2, 3, and 4, respectively. Good agreement is obtained
between simulation and measurement results for the designed
steering angles. The
. In order to
IV. DUAL–POLARIZED ARRAYS
systems, especially in wireless remote sensing and mine detec-
sity, which allows the system to transmit and receive multiple
and/or arbitrary polarizations. Therefore, dual-polarized arrays
of the modified printed bow-tie antenna are designed and their
results are presented in this section.
3070 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 53, NO. 9, SEPTEMBER 2005
Array 2 at (a) 6. (b) 8. (c) 10. (d) 12. (e) 14 GHz.
Comparison between the computed radiation patterns for Array 1 and
Two geometries for dual polarization based on Array 1 and
Array 2, described as configuration 1 and configuration 2,
configuration. (a) Top view for the array of ?
the array of ?
? ?? . (c) Back view for the two arrays. (d) Measured
and computed radiation patterns for the ?
computed radiation patterns for the ? ? ?? array.
Prototypes and results of four-element arrays based on Array 2
? ?? . (b) Top view for
? ?? array. (e) Measured and
configuration 2 of dual polarized array geometries. (a) Return losses. (b) S21.
(c) S31. (d) S41.
Computed return losses and couplings for configuration 1 and
ELDEK et al.: WIDE-BAND MODIFIED PRINTED BOW-TIE ANTENNA3071
configuration 1 and configuration 2 dual polarized arrays with horizontal
ports excited at (a) 6 GHz. (b) 8 GHz. (c) 10 GHz. (d) 12 GHz.
12. Comparisonbetween thecomputed radiationpatterns for
arenumbered 1 and 2, while the vertical ports are numbered
3 and 4. shown in Fig. 10, with a 14-mm separation distance
between elements. Each configuration consists of four printed
modified bow-tie antennas. The horizontal ports are Fig. 11
showsa comparison betweenthereturnlosses andcouplings for
configuration 1 and configuration 2. No significant difference is
noticed in the return losses and couplings. Both configurations
of these antennas operate between 5.5 and 13.5 GHz, and the
highest average coupling is around
patterns when ports 1 and 2 (horizontal ports) are excited are
. The radiation
presented in Fig. 12, at 6, 8, 10, and 12 GHz. As shown in
Fig. 12, the radiation patterns of configuration 1 deteriorate at
10 and 12 GHz, while configuration 2 has lower cross polar-
ization levels, wider beamwidth, symmetrical patterns around
the y-axis, and wider usable bandwidth that includes 12 GHz.
Therefore, configuration 2 is a better candidate for wideband
dual polarized phased array systems.
A wideband modified printed bow-tie antenna is designed for
91% impedance bandwidth that covers the entire C and X bands
radiation pattern and wide usable bandwidth are obtained using
candidate for wideband phased array systems with single linear,
dual linear or circular polarization.
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3072 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 53, NO. 9, SEPTEMBER 2005
Abdelnasser A. Eldek (M’00) received the B.Sc.
degree (with honors) in electronics and communica-
tions engineering from Zagazig University, Zagazig,
Egypt, in 1993, the M.S. degree in electrical engi-
neering from Eindhoven University of Technology,
Eindhoven, The Netherlands, in 1999, with the
cooperation of Philips Center for Technology and
Fontys University for Professional Education (from
1997 to 1999), and the Ph.D. degree in electrical
engineering from The University of Mississippi,
Oxford, in 2004.
He was a Research Assistant with the Department of Microwave, Electronic
Research Institute, Cairo, Egypt, from 1995 to 1996. From January 2001 to De-
cember 2004, he was a Research and Teacher Assistant with the Department of
Electrical Engineering, University of Mississippi. He is currently an Assistant
Professor with the Department ofComputer Engineering, JacksonStateUniver-
sity, Jackson, MS.His currentresearchinterests include electromagnetictheory,
finite difference time domain method, antenna design, and phased arrays.
Dr. Eldek is a Member of the IEEE Antennas and Propagation Society, Mis-
sissippi Academy of Science and Sigma Xi, the honor society of research.
Atef Z. Elsherbeni (S’84–M’86–SM’91) received
the honor B.Sc. degree (with honors) in electronics
and communications, the B.Sc. degree (with honors)
in applied physics, and the M.Eng. degree in elec-
trical engineering, all from Cairo University, Cairo,
Egypt, in 1976, 1979, and 1982, respectively, and
the Ph.D. degree in electrical engineering from
Manitoba University, Winnipeg, Manitoba, Canada,
He was a Research Assistant with the Faculty of
Engineering at Cairo University from 1976 to 1982,
versity. He was a part time Software and System Design Engineer from March
1980 to December 1982 at the Automated Data System Center, Cairo, Egypt.
From January to August 1987, he was a Postdoctoral Fellow at Manitoba Uni-
versity. He joined the faculty at the University of Mississippi in August 1987
as an Assistant Professor of electrical engineering and advanced to the rank of
Associate Professor on July 1991, to Professor on July 1997 and is currently the
Chair of the Engineering and Physics Division of the Mississippi Academy of
Science. He spent a sabbatical term in 1996 at the Electrical Engineering De-
partment, University of California at Los Angeles (UCLA). He has published
65 technical journal articles and 12 book chapters on applied electromagnetics,
antenna design, and microwave subjects, and contributed to 210 professional
presentations. He is the coauthor of the book MATLAB Simulations for Radar
Systems Design (Boca Raton, FL: CRC Press, 2003) and author of the chapters
“Handheld Antennas” and “The Finite Difference Time Domain Technique for
Microstrip Antennas” in Handbook of Antennas in Wireless Communications
(Boca Raton, FL: CRC Press, 2001). He has conducted research in several areas
such as: scattering and diffraction by dielectric and metal objects, inverse scat-
tering, finite difference time domain analysis of passive and active microwave
devices, field visualization and software development for EM education, dielec-
tric resonators, interactions of electromagnetic waves with human body, and
development of sensors for soil moisture and for monitoring of airports noise
levels, reflector antennas and antenna arrays, and analysis and design of printed
antennas for wireless communications and for radars and personal communi-
cation systems. His recent research has been on the application of numerical
techniques to microstrip and planar transmission lines, antenna measurements,
and antenna design for radar and personal communication systems.
Dr. Elsherbeni has honorary memberships in the Electromagnetics Academy
and the Scientific Sigma Xi Society. He received the 1996 Outstanding Engi-
neering Educator of the IEEE Memphis Section, the 2001 Researcher/Scholar
Mississippi, the 2001 Applied Computational Electromagnetic Society (ACES)
Exemplary Service Award for leadership and contributions as Electronic Pub-
lishing managing Editor 1999–2001, the 2002 IEEE Region 3 Outstanding En-
gineering Educator Award, the 2002 School of Engineering Outstanding En-
gineering Faculty Member of the Year Award, and The Mississippi Academy
of Science 2003 Outstanding Contribution to Science Award. He is the past
Chair of the Educational Activity Committee for the IEEE Region 3 Section.
He is the Editor-in-Chief for the Applied Computational Electromagnetic So-
ciety (ACES) Journal, an Associate Editor to the Radio Science Journal, and
the electronic publishing Managing Editor of ACES. He serves on the editorial
board of the Book Series on Progress in Electromagnetic Research, the Electro-
magnetic Waves and Applications Journal, and the Computer Applications in
Engineering Education Journal.
Charles E. Smith (M’59–LM’86–LSM’97) was
born in Clayton, AL, on June 8, 1934. He received
the B.E.E., M.S., and Ph.D. degrees from Auburn
University, Auburn, AL, in 1959, 1963, and 1968,
1968, he was employed as a Research Assistant with
Auburn University Research Foundation. In 1968, he
was an Assistant Professor of Electrical Engineering
with The University of Mississippi, University, and
became an Associate Professor in 1969. He was ap-
pointed Chairman of the Department of Electrical Engineering in 1975, and is
currently Professor and Chair Emeritus of this department. He has directed and
tronics, HF and microwave, computer-aided design, and digital systems courses
and laboratories. His main areas of interest are related to the application of
electromagnetic theory to microwave circuits, antennas, measurements, RF and
wireless systems, radar, digital and analog electronics, and computer-aided de-
sign. His recent research has been on the application of numerical techniques to
microstrip transmission lines, antenna measurements in lossy media, measure-
ment of electrical properties of materials, CAD in microwave circuits, radar de-
signing, and data acquisition using network analyzers. He has published widely
in these areasand has more than200 total publicationsincluding journal papers,
technical reports, book chapters, and paper presentations.
Dr. Smith has advised, or coadvised, 46 M.S. thesis and Ph.D. dissertations,
and has received six awards for outstanding teaching and scholarship at The
University of Mississippi. He is a member of the IEEE Antennas and Propaga-
tionSociety, IEEEMicrowave Theory andTechniques Society, IEEEEducation
Nu, Tau Beta Pi, and Sigma Xi.