A High Gain Bidirectional Circular Polarization
Array Using Bow Tie Antenna Elements for
Applications in Long Confined Space
Yuanyuan Zhang*, Dawei Li, Junhong Wang, Meie Chen, Zhan Zhang, Zheng Li, Yujian Li
Institute of Lightwave Technology, Beijing Jiaotong University
Key Laboratory of All Optical Network & Advanced Telecommunication Network of MOE, Beijing Jiaotong University
Beijing, China
*14120181@bjtu.edu.cn, wangjunh@bjtu.edu.cn
Abstract—A novel high gain bidirectional circularly polarized
array with the same rotation direction on both sides is proposed
in this paper. The array consists of 4 bow tie antennas and
operates at 900 MHz. The 4 bow tie antennas are arranged into
two linearly polarized endfire sub-arrays which are placed
orthogonally, the elements of the two sub-arrays are separated by
a distance of one quarter of the free space wavelength in axial
direction. To feed the array, a strip line on a substrate with a
dielectric constant of 6.0 is used, which makes the guided
wavelength equal to one half of the free space wavelength. The
simulated results show that the impedance bandwidth (S11 < -
10dB) is about 12.8% (836–950 MHz) and the 3 dB axial ratio
(AR) bandwidth (AR < 3dB) is about 50% (700–1170 MHz). The
RHCP gain in the main radiation directions is about 7.3 dBic.
Keywords—bidirectional array; circularly polarization; bow tie
antenna
I. INTRODUCTION
Mobile communication has been extended to various
complex environments to meet the requirement of people for
full coverage of communication, especially for the
communication in confined space. The antennas play an
important role in wireless communication systems, and
different antennas should be selected to achieve the best
system performance for different wireless applications. The
antenna with a bidirectional radiation pattern is suitable for
many application circumstances, such as subways, tunnels of
railway, or narrow street scenarios [1]. The bidirectional
antenna with a high gain can increase the coverage distance
between the neighboring stations, so that the number of
antennas used in the distribute antenna system (DAS) can be
reduced. On the other hand, in order to improve the
communication quality and overcome problems such as
polarization mismatch, multipath fading, time delay, etc.,
circularly polarized antennas are often used. In addition, in
order to match the mobile terminal with fixed circular
polarization direction, the polarization rotation directions on
both sides of the station antennas should be the same.
There are many circular polarization antennas designed for
different circumstances. Microstrip patches and spiral
structures are commonly used in the traditional designs of
circular polarization antennas. However, there are not too
much researches on the bidirectional circular polarization
antenna with same rotation direction on both sides. In addition,
most of the available circular polarization antennas are
designed using multilayer microstrip patches [2]-[4], fed by
microstrip line, coaxial line, or coplanar waveguide (CPW).
Circularly polarized microstrip patch antenna has relatively
simple structure and low-profile, but its narrow bandwidth is
not suitable for applications where wide band properties are
required. In [2], an antenna consists of two rectangular patches
with perturbation segments, which are arranged back-to-back
relative to a CPW on a ground plane, is presented. In [3], an
antenna with two back-to back rotated rectangular patch and
two back-to-back circular patch fed by a slot is proposed.
These two antennas can achieve dual-band, identical left-hand
circular polarization in both front and back directions, and are
suitable for wireless communication in mines. In [4], a
bidirectional circularly polarized antenna for 1.575 GHz
Global Positioning System (GPS) L1 band is presented, which
consists of two back-to-back coupled patches directly fed by a
50Ω CPW. In order to obtain a wide impedance bandwidth, a
pattern reconfigurable circularly-polarized quadrifilar helical
antenna (QHA) with both broadside and backfire radiation
modes is introduced in [5]. The QHA can obtain either
broadside or backfire radiation patterns by controlling the PIN
diodes in the feeding network. However, a large metal plate is
required for this kind of antenna in most cases, which will
bring a large wind resistance and is not suitable for large wind
speed occasions such as tunnels of railway.
A novel feed structure suitable for bidirectional polarized
array antennas of the same sense with little wind resistance is
proposed recently. Its main idea is to feed the two quadrature
linear arrays with a distance of a quarter of a wavelength in
free space with the same phase. In 1964, double side parallel
strip line (DSPSL) was presented [6-8]. It is a balance
structure, which is composed of a dielectric substrate and two
metal strips on two sides of the dielectric substrate. Based on
endfire array and DSPSL, a bidirectional circular polarization
array with the same rotation direction on both sides is
proposed by W. Liu. Two kinds of feed line is employed to
feed the array mentioned above where the phase difference of
any two adjacent points spaced by a quarter of a wavelength in
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