High Gain Antenna
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Transcript of High Gain Antenna
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High Gain Antenna
Antenna Antenna EngineeringEngineering
CHO, Yong HeuiCHO, Yong Heui
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Antenna Antenna EngineeringEngineering
EM Wave LabEM Wave Lab2
Introduction
1. Yagi antenna
Yagi-Uda antenna: parasitic array 1926 at Tohoku University, Japan End-fire traveling-wave antenna
Yagi antenna: one source
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Antenna Antenna EngineeringEngineering
EM Wave LabEM Wave Lab3
Operational principle
1. Yagi antenna
Reflector, driver, and director Input impedance: capacitive or inductive loading Gain: about 10 dBi
)()( ziLjzv
)()( ziC
jzv
)()( zAjzE zz
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Antenna Antenna EngineeringEngineering
EM Wave LabEM Wave Lab4
Introduction
2. Traveling wave
Traveling-wave long wire antenna Beverage antenna (wave antenna): Harold H.
Beverage in 1922 Traveling-wave vee antenna Rhombic antenna
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Antenna Antenna EngineeringEngineering
EM Wave LabEM Wave Lab5
Radiation pattern
2. Traveling wave
Input impedance: almost real Traveling wave: surface wave and leaky wave
Rhombic antenna
zjmeIzI )(
)(sin)( fF
)()()(2/.
2/
cos LfIzdezIf m
L
L
zjk
2/cos
2/cossin)(
Lk
Lkf
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Antenna Antenna EngineeringEngineering
EM Wave LabEM Wave Lab6
Introduction
3. Aperture antenna
Horn antenna: sectoral horn, pyramidal horn, conical horn
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Antenna Antenna EngineeringEngineering
EM Wave LabEM Wave Lab7
4. Reflector antenna
Parabolic antenna
Symmetric mounting- Masking effect: aperture blocking and
diffraction- Spillover: ground noise
Offset mounting- Small antenna: 1 ~ 4 m (diameter)- Spillover: ground noise
Cassegrain mounting- Parabolic and hyperbolic reflectors- Spillover: sky noise
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Antenna Antenna EngineeringEngineering
EM Wave LabEM Wave Lab8
4. Reflector antenna
Cassegrain antenna
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Antenna Antenna EngineeringEngineering
EM Wave LabEM Wave Lab9
Introduction
5. Array antenna
Antenna gain vs. loss- : number of elements- : distance from feeder to element
Array antenna
Nl
dB log3 total2elementarray lNDG Nlm ],/dB[ conductordielectrictotal
DG