Genetically Optimized, Low Profile, Wideband, Shorted Monocone Antenna
Daniel. W Aten, Randy L. Haupt
The Applied Research Lab, State College, PA, USA
E-mail: dwaI26@psu.edu
Introduction
There have been several attempts to design low profile, wideband, vertically
polarized antennas. The monopole wire patch [1] and monopole plate patch [2]
are A I 15 and A I 14 tall respectively, and both have very narrow bandwidth. The
monopolar patch antenna [3] is A111 tall and has a very wide bandwidth. A
similar monocone design with lumped network elements [4] is A I 11 tall and has
a very wide bandwidth.
This paper presents the design of a low profile, wideband, vertically polarized
antenna to be used on an unmanned aerial vehicle (UAV) or airplane in place of
multiple monopole antennas. The new antenna was modeled in Microwave Studio
[5] (MWS) and optimized with a genetic algorithm (GA). The GA minimizedSll
from 800 MHz to 2.4 GHz. Experimental measurements for
pattern compared very well to MWS results.
SII
and the antenna
Antenna Design
Figure 1 is a two dimensional view of the proposed monocone antenna. There are
shorting pins between the points D and F. The variables changed during
optimization are the lines segments depicted in the figure, as well as the number
of shorting pins. The GA used a population size of 8 and mutation rate of 15%.
Figure 2 is a picture of the experimental optimized antenna. It is A/14.7 tall at
800 MHz and AI5 tall at 2.4 GHz. It is shorter than a resonant quarter wave
monopole at any frequency in its bandwidth. Figure 3 is a plot of SII comparing
the MWS results to the experimental results. The antenna has an SWR<2 from
800 MHz to 2.4GHz. The computed results closely matched the experimental
results.
Figure 4 compares the MWS and experimental antenna patterns taken at four
different frequencies. Figure 4a through Figure 4d are patterns taken from
¢ = 0: 360 at (I = 90 These show that the antenna is predominantly theta
polarized and is omnidirectional across its operating bandwidth. Figure 4e
through Figure 4f are antenna patterns taken from (I = 0: 360 at ¢ = 0 It can be
seen that as frequency increases the peak of the main beam squints away from the
ground plane as a function of (I .
0
0
•
0
978-1-4244-3647-7/09/$25.00 ©2009 IEEE
0
•
c
T
D
E
u.
o
F
A
~AC - + C D
+ +
DE
G
EG-1
Figure 1. Proposed antenna geometry which shows the optimization variables
Figure 2. Final antenna design which was used as the experimental antenna
-MWS Results
••- Measured
-5
co
-10
~
-20
-25
0.5
0.75
1.25
1.5
1.75
Frequency (Hz)
2
2.25
2.5
9
x 10
Figure 3. S•• of the experimental antenna compared to MWS
180
a) Antenna pattern at 1.0 GHz,
0
~=0:360° at 8=90
b) Antenna pattern at 1.5 GHz,
0
~=0:360° at 8=90
00
330
30
3~
.0
.:...."'''.''''.'(
270
90
;
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i
;
;
90
270i~"'"
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24~
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//120
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.
.'
.'
~
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210 ."'.... ~.~.~.=
180
180
c) Antenna pattern at 2.0 GHz,
0
~=0:360° at 8=90
00
210
,
'
.:. .
150
d) Antenna pattern at 2.4 GHz,
0
~=0:360° at 8=90
150
210
150
180
180
e) Antenna pattern at 1.0 GHz,
8=0:360 0 at ~=Oo
f) Antenna pattern at 1.5 GHz,
8=0:360 0 at ~=Oo
60 .
3~_
\
300
270
240
~
···Wr-.-··/
210
T
330 ••
300
60
90
120
150
00
,.~
'vt~20
60
!i
90
270
240
120
210
150
180
180
g) Antenna pattern at 2.0 GHz,
8=0:360 0 at ~=Oo
h) Antenna pattern at 2.4 GHz,
8=0:360 0 at ~=Oo
- - - - -Eo -Measured
- · - · - · Eo -MWS
- - - - E~ - Measured
E;-MWS
Figure 4. Experimental antenna patterns compared to MWS results
Conclusion
This paper has presented the design resulting from the GA optimization of a
broadband monocone with shorting pins for use on a UAV. The results of the
optimization yielded an antenna which is A/14.7 tall and operates over a
frequency range of 800 MHz to 2.4 GHz. The final design can replace 12
corresponding monopoles on a UAV while being lower profile.
Acknowledgments
This work was sponsored by ONR under contract NOOO 14-05-G-0106/0010
The authors would like to thank Mike Foust for overseeing the fabrication process
of the experimental antenna.
The authors would like to thank Tim Eden and Joe Flemish of Penn State ARL for
their support and Atef Elsherbeni of University of Mississippi for performing the
antenna pattern measurements
References
[1] Ch. Delaveeaud, Ph. Leveque, B. Jecko, "New Kind of Microstrip Antenna:
the Monopolar Wire-Patch Antenna," Electronic Letters, vol. 30, no.1, pp. 12, Jan. 1994.
[2] Jeen-Sheen Row, Shih-Huang Yeh, Kin-Lu Wong, "A Wide-Band
Monopolar Plate-Patch Antenna" IEEE Transaction on Antennas and
Propagation, vol. 50, no. 9, pp. 1328-1330, Sep. 2002.
[3] Ka-Leung Lau, pei Li, Kwain-Man Luk, "A Monopolar Patch Antenna with
Very Wide Impendence Bandwidth," IEEE Transactions on Antennas and
Propagation, vol. 53, no. 3, pp. 1004-1010, Mar. 2005.
[4] Yu Yu Kyi, Li Jianying, Gan Yeow Beng, "Broadband Characteristics of
Small Disc Cone Antennas" IEEE Antennas and Propagation Conference
2007, pp. 4769-4772, June 2007
[5] CST Microwave Studio, Version 2006B. OS, April 19, 2006