Download Improvement of a Tear Drop-Shaped Antenna with an

EMC’09/Kyoto
23R2-4
Improvement of a Tear Drop-Shaped Antenna with
an Optical Feeding Using a Dielectric
Reinforcement
Shingo INOUE#1,Hideki ABE#1, Masamitsu TOKUDA#1,Shinobu ISHIGAMI#2,
#1Electrical Engineering, Research Division in Engineering
Musashi Institute of Technology
1-28-1 Tamazutsumi,Setagaya-Ku, Tokyo, 158-8557 Japan
(ahideki, tokuda)@csl.ec.musashi-tech.ac.jp
#2EMC Group, National Institute of Information and Communications Technology
4-2-1 Nukuikitamachi, Koganei-shi, Tokyo, 184-8795 Japan
[email protected]
Abstract— A tear drop-shaped antenna combined spherical and
biconical antenna elements had been developed in order to
obtain the radiated wideband emission source having directivity
specified by CISPR 16-1-4Ed.2 above 1 GHz. In this paper, an
improved tear drop-shaped antenna using a dielectric
reinforcement was proposed. The effect of the reinforcement that
was made from acrylic fiber (permittivity=3.0) is calculated by
the finite integration (FI) method. The calculated result was
compared with the measured ones. The upper and lower element
of the tear drop-shape antenna is reinforced by a cylindrical
acrylic fiber of which thickness is 30 mm. The tear drop-shaped
antenna with no reinforcement (conventional model) did not
meet the requirement of CISPR standard. In contrast, E-plane
radiation patterns obtained by the calculation and measurement
were improved at ș=0 and 180 degrees in the case of the tear
drop-shaped antenna with the reinforcement mentioned above.
The tear drop-shaped antenna with the proposed reinforcement
satisfies the directivity specified in CISPR 16-1-4 Ed.2 in a
frequency range from 1 GHz to 6 GHz.
Key words: tear drop-shaped antenna, biconical antenna, optical
feeding method, CISPR 16-1-4, finite integration method
signal but also an optical power simultaneously. The antenna
has a special O/E conversion element named as uni-travellingcarrier photodiode (UTC-PD). The developed antenna has a
shape with combining a hemisphere and a biconical antenna
element. It was clarified that the characteristics of the antenna
met the requirement of CISPR 16-1-4 the second edition in
frequency band from 1 GHz to 6 GHz[2][3]. However, it is
difficult to use the antenna actually because there is structural
weakness in the feeding part without reinforcement. In this
paper, an improved tear drop-shaped antenna using a
dielectric reinforcement was proposed. The effect of the
reinforcement is calculated by the finite integration (FI)
method. The calculated result was compared with the
measured ones.
II. CISPR REQUIREMENT FOR MEASUREMENT SITE ABOVE 1
GHZ
To measure an emission from the electric equipment
causing EMI, an open area test site (OATS) or an anechoic
room that is an alternative site of OATS, in which there are no
I. INTRODUCTION
reflection objects, is required. In this examination an anechoic
Recently, electronic and electric equipment including room was used. The anechoic room has seven sides, and the
telecommunication equipment is widely used with the pyramid-shape microwave absorbers and ferrite tiles are
incredible advances in technology. However, an installed for each side. The absorbers are made from ferrite.
electromagnetic interference (EMI) problem arises as the The evaluation method in 30 MHz to 1 GHz has already stated
technology advances. The electromagnetic radiation from in CISPR 16-1-4. A new paragraph was added to CISPR 16-1industrial, scientific and medical (ISM) equipment, home 4 concerning an evaluation method of the EMI measurement
appliances, and information equipment may interfere to other site above 1 GHz and CISPR 16-1-4 Ed. 2 was published in
electronic equipment. In international special committee on February 2007. An ideal EMI examination site below 1 GHz
radio interference (CISPR), a new paragraph (Paragraph 8.2) has an infinite volume with an infinite ground plane. The
was added to CISPR 16-1-4 concerning an evaluation method characteristics of the anechoic room were examined by
of the EMI measurement site above 1 GHz and the comparing between the site attenuation of the room and that of
international standard had been published as CISPR 16-1-4 Ed. the ideal site. In contrast, entirely free space or semi-free
2 in February 2007 [1]. The frequency range of the space with microwave absorbers on the ground plane is used
conventional international standard was from 30 MHz to 1 as an ideal site of the EMI examination above 1 GHz. In the
GHz.
case, the directivity of the transmitting antenna is important. A
The authors had developed a new type of antenna using the wide directivity in the direction of ș like the dipole antenna
optical power feeding that can supply not only an optical
Copyright © 2009 IEICE
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EMC’09/Kyoto
23R2-4
and circular symmetry in the direction of ij is required as
shown in Figure 1.
Direction of 䃗
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㻙㻡Prohibited
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Directivity in 㻝㻜㻡㼻
requirements
Direction of 䃥
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IV. DIRECTIVITY OF THE TEAR DROP-SHAPED ANTENNA WITH
NO REINFORCEMENT )
Figure 3 shows the simulation result of the directivity in ș
direction of 1.6 GHz in the tear drop-shaped antenna as shown
in Fig. 2 with the element radius of 50 mm. The directivity in
ș=0 and 180 degrees at the frequency of 1.6 GHz in does not
meet the requirement of CISPR standard. However, the
directivity in other ș directions meets the requirement from 1
GHz to 6 GHz except for 1.6 GHz. It is confirmed that the
directivity in ij direction also meets the requirement with the
frequencies from 1 GHz to 6 GHz.
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㻙㻥㻜㼻
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area
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Prohibited 㻝㻞㻜㼻
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㻯㻵㻿㻼㻾㻝㻢㻙㻝㻙㻠㻱㼐㻚㻞
Fig.1 Directivities stated in CISPR16-1-4Ed.2.
Fig.3 Directivity in ș directionat 1.6 GHz.
III. SIMULATION METHOD
In this paper, MW-Studio [4] was used in the numerical
simulation of the FI method. The integral forms of the
Maxwell equation are used in the method. Figure 2 shows the
simulation model of the tear drop-shape antenna. The element
of the antenna has a structure of a combination of a spherical
element and a biconical antenna element. Generally, an
antenna with the biconical-shape elements is known as a
broadband antenna. The radius of the spherical part of the
antenna is 50mm. The cell sizes of the numerical simulation
using the FI method are determined automatically by the code,
all boundary conditions are assumed to be free space.
100䡉䡉
50mm
234mm
Feeding point
V. REINFORCEMENT OF TEAR DROP-SHAPED ANTENNA
There is another problem about the conventional antenna as
shown in Fig. 2 except for the compliance for the requirement
of the CISPR standard. The problem is a strength poverty of
the feeding part. In this study, an improvement of the structure
of the antenna was examined without degrading the
specifications of the antenna.
In the conventional studies, a cylindrical dielectric material
(Teflon) with 30 mm in thickness was the best reinforcement
material according to the result of the numerical simulation.
However, Teflon is costly. Therefore, an acrylic fiber was
used as an alternative reinforcement material. The permittivity
of the acrylic fiber is not so different with that of Teflon, and
the acrylic fiber is not costly.
The antenna with the acrylic-fiber reinforcement was
assembled experimentally. Figure 4 shows a model of the
antenna with reinforcement material. Since the 5 mm gap
exists between the antenna and the reinforcement, the styrene
foam with the doughnut shape was used for bridging the gap.
Copper
Fig.2 Simulation modelwith no reinforcement.
Copyright © 2009 IEICE
608
EMC’09/Kyoto
23R2-4
䠑䠌䡉䡉
䠏䠌䡉䡉
Styrene foam
(5mm thickness)
Front view
Top view
Cross section
reinforcement antenna model (Acrylic fiber: 30mm thickness)
in Fig.6. A result of the numerical simulation was compared
with the measurement result in the case of the directivity in ij
direction (1.6 GHz). It is confirmed that the both of results
meet the requirement of CISPR standard in the cases of the ș
and ij directions. Moreover, the result of the numerical
simulation agreed well the measured ones. It is also confirmed
that the directivities meet the requirement of the CISPR
standard at the frequencies from 1 GHz to 6 GHz. Therefore,
the proposed antenna can be used for the transmitting antenna
of the CISPR EMI measurement.
Fig.4 Antenna model with reinforcementthat made from acrylic fiber with
30 mm in thickness.
VI. RADIATION PATTERNS
Figure 5 shows the setup for measurement of a radiation
pattern of the tear drop-shaped antenna with reinforcement
material. The measurement of the radiation pattern was
conducted in the anechoic room with seven sides. The antenna
is proposed as the transmitting antenna. The feeding power is
-2 dBm through the UTC-PD and the optical fiber. The
electric field radiated from the antenna was detected with
double ridged guide horn antenna. The detected power was
measured with a spectrum analyzer. The transmitting antenna
is installed on the turntable and the support stand, of which
height is 1 m. In addition, a distance between the transmitting
antenna and receiving antenna is 1 m. When the radiation
pattern is measured, the antenna is rotated by the turntable
every 5 degree.
Transmitting
㏦ಙ࢔ࣥࢸࢼ
antenna
Double
ridged
ࢲࣈࣝࣜࢪࢵࢺ
guide
horn antenna
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Optical
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amplifier
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Source
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(1.55䃛m)
ಙྕ
Signal
䝅䜾䝘䝹
Signal
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generator
Coaxial
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cable
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㻯㼍㼘㼏㼡㼘㼍㼠㼕㼛㼚
㻹㼑㼍㼟㼡㼞㼑㼐
Fig.6 Directivity in ș direction(1.6GHz).
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㻙㻝㻜㻡㼻 㻢
㻙㻣㻡㼻
㻙㻢㻜㼻
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㻙㻠㻡㼻
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㻹㼑㼍㼟㼡㼞㼑㼐
䝇䝨䜽䝖䝹
Spectrum
analyzer
䜰䝘䝷䜲䝄
Fig.7 Directivity in ȭ direction(1.6GHz).
䝞䜲䜰䝇
Bias
B. Frequency characteristics of radiated fields
Figure 8 shows the measurement and calculation results of
Fig.5 Setup for measurement of radiation patterns.
the frequency characteristics of the radiated fields. As a result,
the measured characteristics almost agreed with ones by the
numerical simulation except for the vicinity of 2 GHz. It is
A. Radiation pattern
clarified that the improved tear drop-shape antenna is
The measured radiation patterns are shown in Figs. 6. and 7. applicable as a wideband transmitting antenna.
The directivity in ș direction (1.6 GHz) by the numerical
simulation was compared with the measurement result for the
Copyright © 2009 IEICE
609
㻱㻙㼒㼕㼑㼘㼐㻌㼟㼠㼞㼑㼚㼓㼠㼔㼇㼐㻮䃛㼂㻛㼙㼉
EMC’09/Kyoto
23R2-4
㻝㻞㻜
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VII.
CONCLUSION
We have developed a tear drop-shaped antenna combined
spherical and biconical antenna elements, in order to obtain
the radiated wideband emission source having directivity
specified in CISPR 16-1-4 Ed.2 above 1 GHz. In this paper,
an improved tear drop-shaped antenna using a dielectric
reinforcement was proposed. The effect of the reinforcement
that was made from acrylic fiber (permittivity=3.0) is
calculated by the finite integration (FI) method. The
calculated result was compared with the measured ones. As a
result, the followings were clarified.
㻹㼑㼍㼟㼡㼞㼑㼐
㻯㼍㼘㼏㼡㼘㼍㼠㼕㼛㼚
㻝
㻞
㻟
㻠
㻡
㻢
㻲㼞㼑㼝㼡㼑㼚㼏㼥㼇㻳㻴㼦㼉
Fig.8 Frequency characteristics of radiated fields
C. VSWR
Figure 9 shows the measurement and calculation results of
the VSWR for a comparison. The measured and calculated
VSWR responses have almost same qualitative nature.
However, the values of VSWR are somewhat different
between both of results. The difference may be caused by the
“mediocre” machining accuracy of the antenna and by the
imperfect treatment of the styrene foam in the simulation
model.
㼂㻿㼃㻾
㻡
㻯㼍㼘㼏㼡㼘㼍㼠㼕㼛㼚
㻹㼑㼍㼟㼡㼞㼑㼐
㻠
(1) Both of directivity in ș direction and directivity in ij
direction met the requirement of the CISPR standard from
1 GHz to 6 GHz using the cylindrical acrylic
reinforcement (30 mm in thickness). These results were
confirmed from both of calculation and measurement
results.
(2) The measured frequency characteristics almost agreed
with ones by the numerical simulation except for the
vicinity of 2 GHz. It is clarified that the improved tear
drop-shape antenna is applicable as a wideband
transmitting antenna.
(3) The measured and calculated VSWR responses have
almost same qualitative nature. However, the values of
VSWR are somewhat different between both of results.
The difference may be caused by the “mediocre”
machining accuracy of the antenna and by the imperfect
treatment of the styrene foam in the simulation model.
As a result, it is confirmed that the reinforced tear dropshape antenna has a practical use for the transmitting antenna
specified in CISPR16-1-4 Ed.2 in every aspects, which is the
directivity, frequency characteristics, and VSWR.
㻟
㻞
REFERENCES
[1]
㻝
㻜
㻝
㻞
㻟
㻠
㻡
㻢
[2]
㼒㼞㼑㼝㼡㼑㼚㼏㼥㼇㻳㻴㼦㼉
Fig.9 VSWR of the antenna.
[3]
[4]
Copyright © 2009 IEICE
610
CISPR16-1-4 Ed.2, 8: Test site for measurement of radio disturbance
field strength for the frequency range 1GHz to 18GHz, 8.2: Validation
of the test site, 2007-02.
H. Tanaka, S. Itakura, Y. Okano and M. Tokuda: An optical feeding
antenna with wide bandwidth for evaluation of radiated emission test
site above 1 GHz, emc europe 2006 barcelona, International
Symposium on Electromagnetic Compatibility, Barcelona, Spain,
pp.739-744, 2006.
H. Abe, H. Tanaka, M. Tokuda and S. Ishigami: An optical feeding
antenna with wide bandwidth for evaluation of radiated emission test
tite
above
1
GHz,
2008
IEEE
EMC
International
Symposium,Detroit,WED-AM-6-OF-2,2008.
CST microwave studio, 2008 See URL http://www.cst.com/.