High Gain Antenna

Antenna Antenna EngineeringEngineering

CHO, Yong HeuiCHO, Yong Heui

Antenna Antenna EngineeringEngineering

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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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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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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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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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Introduction

3. Aperture antenna

Horn antenna: sectoral horn, pyramidal horn, conical horn

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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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4. Reflector antenna

Cassegrain antenna

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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