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Impedance

Matching

AntennaAntenna

EngineeringEngineering

CHO, Yong HeuiCHO, Yong Heui

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 1. Impedance Matching

 Basic Concept

Voltage or Current → atio is a !e" #actor

$oad

%a&e

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 Ma'imum po(er trans#er

 1. Impedance matching

Condition for maximum power transfer -  

Matching network

- Usually source and load are fixed.

Reflection

- Conjugate matching doesn’t mean no

reflection.

No reflection-  

  *0   )(  L Z  Z    =

 L Z  Z    =

0

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출처 ) *AI+

 1. Impedance Matching

 Varia-le hase +hi#ter

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 Matching (ith lumped elements

Compact sie !ifficulties in finding the proper "alue of # or C #-network$ %-network$ and -network

Π

 1. Impedance matching

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 rocedure) $/net(or! 

!efine

!raw

&ind to intersect the

circle

!raw

&ind to cancel out

  0/ Z  Z  z   L L  =

 L L   z  y   /1=

 jx z  L   +=1

11   =++=   jX  jx z in

 jB

 L z 

 jX    jx

 1. Impedance matching

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 E'ample

!esign the # section matching network to

match the transmission line$

  where

[ ] [ ]   MHz  f   Z  j Z  L   500,100,100200 0  =Ω=Ω−=

+mith chart

 1. Impedance matching

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 +ingle/stu- matching

'pen stu( and short stu(

+hort stu- 0$

Open stu- 0C

 1. Impedance matching

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 +ingle/stu- matching

)imple matching network

+mith chart

 1. Impedance matching

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 rocedure) shunt stu-

!efine

!raw

Mo"e to the direction of

generator 

&ind the intersection of the

circle

*djust the length of a shunt

stu(

  0/ Z  Z  z   L L  =

 L L   z  y   /1=

 jb y L   +=1

 jb yS    −=11   =−+=

+=

 jb jb

 y y y S  Lin

 1. Impedance matching

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 2ou-le/stu- matching

&ixed length (etween the load and stu(

+mith chart

 1. Impedance matching

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 3uarter/(a&e trans#ormer

+asy calculation of the matching network Narrow (andwidth characteristics

4/,01   λ ==   l  Z  Z  Z   L

 1. Impedance matching

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 ransitions

Complicated design procedure ,road (andwidth characteristics %he theory of small reflections

,inomial multisection line Che(yshe" multisection line %apered line

 1. Impedance matching