lecture04a_antenna types.pdf
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Antenna EngineeringLecture 4: Antenna Types and Analysis Techniques
Part I
ELC 405a Fall 2011
Department of Electronics and CommunicationsEngineering
Faculty of Engineering Cairo University
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Antenna TypesBy Current Distribution
By Material
By Geometry
Analysis of Some Antennas
Dipoles, Monopoles and Loops
Folded Dipole
Helical Antenna
Islam A. Eshrah, 2009
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Outline
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Antenna Types Analysis of Some Antennas
By Current Distribution
Islam A. Eshrah, 2009
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Standing and Traveling Wave Antennas
Standing Wave Traveling Wave
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I
Standing-wave antennas are usually narrow-band antennas.Traveling wave antennas are usually wide-band antennas.
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Antenna Types Analysis of Some Antennas
By Geometry
Islam A. Eshrah, 2009
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Line, Surface and Volume Antennas
Line Surface Volume
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Antenna Types Analysis of Some Antennas
Antenna TypesBy Current Distribution
By Material
By Geometry
Analysis of Some Antennas
Dipoles, Monopoles and Loops
Folded Dipole
Helical Antenna
Islam A. Eshrah, 2009
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Outline
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2
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Antenna Types Analysis of Some Antennas
Wire Antennas
Islam A. Eshrah, 2009
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Dipole, Monopole and Loop Antennas
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The sinusoidal approximation can be adopted to estimate the parameters of theantennas above.
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Antenna Types Analysis of Some Antennas
Wire Antennas
Islam A. Eshrah, 2009
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Folded Dipole
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V V /2 V /2
I 1 I 2
1 11 2 122V I Z I Z
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1
4in
V Z Z
I
The folded dipole is typically used with the two-wire line (matching impedance).
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Antenna Types Analysis of Some Antennas
Wire Antennas
Islam A. Eshrah, 2009
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Helical Antenna
140in
R C 20
15
D nC S 52
HPBW
C nS
The helical antenna operates in the axial mode as a predominantly traveling waveantenna with the circumference measuring one wavelength and the turn spacingmeasuring quarter wavelength.
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Antennas may be categorized by current distribution, geometryand material.
Wire antennas such as dipoles and loops may be approximatelyanalyzed by adopting the sinusoidal approximation.
Folded dipoles have 4 times the input impedance of thecorresponding dipole.
Traveling wave antennas (e.g. helical antennas) have in generalbroader bandwidth and higher directivity than thecorresponding standing wave antennas.
Islam A. Eshrah, 2009
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Conclusion