482 IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, VOL. 14, 2015
Dual-Circularly Polarized Conical-Beam Microstrip
Antenna
Xudong Bai, Xianling Liang, Member, IEEE, Minzhu Li, Bin Zhou, Junping Gen
g, Member, IEEE,and
Ronghong Jin, Senior Member, IEEE
Abstract—A dual-circularly polarize d (CP) microstrip antenna
with conical-beam radiation is presented in this letter. The antenna
is excited at the second-order mode to generate the conical radia-
tion pattern and is fed by a hybrid coupler to obtain the dual-CP
operation, w hich shows a stable performance with varisized metal
reflectors. The measured results are consistent with the simulated
ones in terms of good dual-CP conical patterns, which verified the
effectiveness of the proposed design. All these features make the
proposed antenna very suitable for vehicle-mounted satellite com-
munication applications.
Index Terms—Circular polarization, conical pattern, satellite
communication, secon d-order.
I. INTRODUCTION
I
N RECENT years, there h as been a lot of interest in almost
all the fields related to satellite communicat ion app licat ions,
where vehicle-mounted antenna
salsoplayamorecrucialrole
on the overall performance. Satell ite co mmunication systems
usually require the antenna to provide several key performances,
such as wide beam, circular po
larizations (CPs), and high gain
at low elevatio n [1] .
Microstrip antennas, d ue to the advantages of low cost, low
profile, and easy processin
g, have been widely used in satel-
lite communication; and for m ost CP microstrip antennas, the
peak direction of the radiation pattern is vertical to the antenna
plane [2]–[4]. Howev e
r, the elevation angles of the satellite seen
from the ground are always tilted from the boresight direction ;
for example, the elevation angle changes from 24.4
to 67.3
in China with about 4
6
as an average [5]. This means the top
zone of the highest gain is w asted in some sense. Thus, antennas
with CP co nical patterns are strongly demanded, and microstrip
antennas operat
ed at the second-order mode may be one good
choice. In [6], the basic principle and method of exciting the
second-order mode and generating CP conical patterns of mi-
crostrip ante
nnas is studied and analy zed. Then, to p ut the prin -
ciple to practical use, a hybri d feeding m echanism is proposed
Manuscript received July 21, 2014; revised August 28, 2014 and October
16, 2014; accepted November 04, 2014. Date of publication November 11,
2014; date of current version February 06, 2015. This work was supported
by the National Science and Technology of Major Project under Grant
2011ZX03001-007-03, the National Natural Science Foundation under Grant
61201058, the Research and Innovation Project of Shanghai Education
Commission under Grant 12Z112030001, the State Quality In spection Admin-
istration of Science and Technology Project under Grant 2013QK127, and the
Project of “SM C Excellent Young Faculty.”
The authors are with the Department of Electronics E ngineering, Shanghai
Jiao Tong University, Shanghai 200240, China (e-mail: liangxl@sjtu.edu.cn).
Color versions of one or m ore o f the figures in this letter a re available online
at http://ieeexplore.ieee.org.
Digital Object Ide ntifier 10.1109/LAWP.2014.2369515
Fig. 1. Antenna g eometry. (a) Layer ed view. (b) Side view. (c) Upward 2-D
view.
Fig. 2. Current d
istribution of the parasitic patch operated at second-ord er
mode. (a) Witho
ut the star-shaped slot. ( b) With the star-shaped slot.
to feed the conical-beam antenna and to get the wideband oper-
ation[7].Tofulfil the demand of polarization diversity in satel-
lite commun
ication, the conical-beam antenna can be further ex-
tended through dual-CP operation.
In th is letter, a dual-CP conical-beam microstrip antenna op-
erated at
the second-order mod e is proposed, and a bottom metal
reflector instead of the car roof is also added underneath t o sim-
ulate the vehicle en vironm ent. The an tenna is a good candidate
for veh
icle-mounted satellite comm unication systems, with the
peak radiation direction pointing to the satellite. The reminder of
this letter is organized as follows: Section II presents the antenna
struc
ture and design. Section III discusses the measured results,
including bandwidth, radiation pattern, and axial ratio (AR).
Section IV gives the conclusions.
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