Forum for Electromagnetic Research Methods and Application Technologies (FERMAT) Electromagnetic Simulation for Education on Antenna Engineering By Mitsuo Taguchi Graduate School of Engineering Nagasaki University Nagasaki, Japan [email protected]Abstract: For the purpose of the teaching of antenna for the undergraduate students, the time domain response of near field distribution of dipole antenna excited by Gaussian monocycle pulse generator is shown. Then a centrally fed slot antenna on the rectangular conducting plane is calculated and shown how the equivalent magnetic current is induced on the slot. In the numerical analysis, the electromagnetic simulator WIPL-D based on the Method of Moments is used. Keywords: Slot antenna; simulation; electromagnetic simulator; Method of Moments References: [1] M. Taguchi, “Possibility of instruction by electromagnetic simulators for electromagnetic wave education,” Journal of IEICE, Japan, vol. 96, no. 1, pp. 41-45, Jan. 2013 (in Japanese). [2] J. Anguera, et. al., “Antenna theory education tool using an interactive and movie-based electronic book”, Proc. of 37th ASEE/IEEE Frontiers in Education Conference, pp. S2C-8-S2C-13, Oct. 2007. [3] M. Mazanek, et. al., “Education in antennas wave propagation and microwave techniques”, Proc. of 18 th International Conference on Applied Electromagnetics and Communications, pp. 1-4, 2005. [4] M. Taguchi and H. Goto, “Animation of electromagnetic wave radiation from wire antenna,” ITE Technical Report, BCT2012-7, Jan. 2012 (in Japanese).” [5] M. Taguchi and Hirotaka Oba: “Circular polarized antenna composed of unbalanced fed ultra low profile inverted L antenna and slot”, Proc. of 2014 IEEE AP-S/URSI, 429-6, July 2014. [6] M. Taguchi and K. Imayoshi: “Animation of electromagnetic wave radiation from slot anetnna”, ITE Technical Report, BCT2014-15, Jan. 2014 (in Japanese). [7] http://www.wipl-d.com/. [8] S. Silver. “Microwave antenna theory and design”, p.88, McGraw-Hill, 1949.
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Forum for Electromagnetic Research Methods and Application Technologies (FERMAT)
Outline of Presentation1. Introduction2. Animation of electromagnetic wave
radiation from dipole antenna3. Analytical model of slot antenna4. Numerical results and discussion5. Conclusion
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Recently, due to the development of the graphics processingunit and the animation tools in the electromagneticsimulators, the user can see the near field distribution orcurrent distribution on the antenna in addition to theinput impedance and the radiation characteristics, andunderstand the antenna characteristics intuitively [1].Therefore the electromagnetic simulators and the animationtools are useful tool in the education of electromagneticwave theory and the antenna engineering for theundergraduate students.
1. Introduction
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We have analyzed the time response of the near fielddistribution of the dipole antenna excited by the Gaussianmonocycle pulse generator, and showed how the electricand magnetic fields are excited near antenna [4].Since the dipole and the slot are the element antennas of thecircularly polarized antenna [5], the phenomenon ofelectromagnetic field on slot antenna have to be shown.
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In this presentation, The time domain response of near field distribution of dipole antenna excited by Gaussian monocycle pulse generator will be shown [4]. A centrally fed slot antenna on the rectangular conducting plane will be calculated and shown how the equivalent magnetic current is induced on the slot [6]. In the numerical analysis, the electromagnetic simulator WIPL-D based on the Method of Moments is used [7].
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2
5Feed point
135
Unit [mm]
3. Animation of electromagnetic wave radiationfrom a dipole antenna [4]
Half-wave dipole antenna
Gaussian mono cycle pulse voltage is fed.(Center frequency:
500 MHz)
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‐1.0
‐0.5
0.0
0.5
1.0
0.0 1.0 2.0 3.0 4.0
Wav
e fo
rm [V
]
time [nS]
20
0 2ex p2
-t - tef t A t t
0
1.0,0.318 nS, 2.0 nS
A
t
Gaussian mono cycle pulse voltage
Center frequency: 500 MHz
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Time response of electric field
1.0nS 1.2nS 1.4nS 1.6nS 1.8nS 2.0nS 2.2nS [V/m]
2.4nS 2.6nS 2.8nS 3.0nS 3.2nS 3.4nS 3.6nS
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Time response of magnetic field
1.0nS 1.2nS 1.4nS 1.6nS 1.8nS 2.0nS 2.2nS [mA/m]
2.4nS 2.6nS 2.8nS 3.0nS 3.2nS 3.4nS 3.6nS
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[V/m]
[mA/m]
Electric field Magnetic field
Near field distribution
Strongly excited
Strongly excited
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Fresnel and far-field region
[V/m] [mA/m]
Electric field Magnetic field
222
Dr Boundary between Fresnel
and Far-field region
Electric field is proportional to magnetic field in far-field region
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Slot
model 1:w=3mm, L=280mmmodel 2:w=6mm, L=270mmmodel 3:w=12mm, L=250mm
3. Analytical model of slot antenna
Fig. 1. Slot antenna.
Frequency: 500 MHz
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4. Numerical results and discussion
[A/m]
[A/m]
Fig. 2. Current distribution on conducting plane.
Feed point
Feed point
(a) Model 1 Maximum value of current amplitude = 3.69 A/m.
(b) Model 3 Maximum value of current amplitude = 2.17 A/m.
Current distribution on conducting plane.
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Model 3
Model 2
Model 1
Z component of magnetic field
[A/m]
x
y
Feed point
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Amplitude distribution of magnetic field on central axis of slot
Observation point
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Model 1
Model 2
Model 3
X component of electric field
[V/m]
x
y
Feed point
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X component of electric field along x axis
Amplitude is inversely proportional to slot width.Directivity is almost same in three models.
Amplitude distribution of electric field (x component) on central axis of slot
Observation point
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J:Current on conducting plane:Equivalent magnetic current on slot
n:Unit normal vector on slot:Unit vectors along r, θ, φ direction
:Position vector of source point
, exp4 r r m r r
S
j jk dS
D J J i i J i i i
Electric field at in Far-field region , ,r
m J E n
exp, , ,
jkrr =
r
E D
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n
Electric field Es is induced within slot.
Equivalent magnetic current Jmis defined by
x
y
Electric field in far-field region
. m sJ E n
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feed point slot
[mA/m]
Fig. 3. Current vector distribution of Model 3.
Current vector distribution of Model 3.
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Current flows on circumference of slot.
Currents on opposite sides flow opposite directions each other. This means that current on conducting plane does not contribute to radiation field.
J
Electric field is expressed in terms of integration of equivalent magnetic current.
x
y
, exp4 r r m r r
S
j jk dS
D J J i i J i i i
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5. Conclusion
The slot antenna on the rectangular conducting plane iscalculated and the current distribution on the conductingplane and the equivalent magnetic current within slot areshown for the purpose of the teaching of antenna for theundergraduate students. In the slot antenna, the currentflowing along the slot edge decides the equivalent magneticcurrent within slot.
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REFERENCES[1] M. Taguchi, “Possibility of instruction by electromagnetic simulators for
electromagnetic wave education,” Journal of IEICE, Japan, vol. 96, no. 1, pp.41-45, Jan. 2013 (in Japanese).
[2] J. Anguera, et. al., “Antenna theory education tool using an interactive andmovie-based electronic book”, Proc. of 37th ASEE/IEEE Frontiers in EducationConference, pp. S2C-8-S2C-13, Oct. 2007.
[3] M. Mazanek, et. al., “Education in antennas wave propagation and microwavetechniques”, Proc. of 18th International Conference on Applied Electromagneticsand Communications, pp. 1-4, 2005.
[4] M. Taguchi and H. Goto, “Animation of electromagnetic wave radiation fromwire antenna,” ITE Technical Report, BCT2012-7, Jan. 2012 (in Japanese).
[5] M. Taguchi and H. Oba: “Circular polarized antenna composed of unbalancedfed ultra low profile inverted L antenna and slot”, Proc. of 2014 IEEE AP-S/URSI, 429-6, July 2014.
[6] M. Taguchi and K. Imayoshi: “Animation of electromagnetic wave radiationfrom slot antenna”, ITE Technical Report, BCT2014-15, Jan. 2014 (in Japanese).
[7] http://www.wipl-d.com/.[8] S. Silver. “Microwave antenna theory and design”, p.88, McGraw-Hill, 1949.