Impedance Matching

Matching

Microwave Engineering

CHO, Yong Heui

Phase shifter

 Condition -

 Matching network

 Reflection

 No reflection -



0

( Z

) Z 

Z

Z



출처: KAIST

 Compact size

 Difficulties in finding the proper value of L or C

 L-network, T-network, and -network





 Define

 Draw

 Find to intersect the circle

 Draw

 Find to cancel out

 ^z

^{ Z}

^{/ Z}

L

L

z

y  1 /

jx z

 1 

1

1   

 jx jX z

jB

z

jX jx

 Design the L section matching network to match the transmission line,

where



  ^Z   ^{f MHz}

j

Z

 200  100  ,

 100  ,  500

Smith chart

 Open stub and short stub



Short stub (L)

Open stub (C)

 Simple matching network



Smith chart

 Define

 Draw

 Move to the direction of generator

 Find the intersection of the circle

 Adjust the length of a shunt stub

 ^z

^{ Z}

^{/ Z}

L

L

z

y  1 /

jb y

 1 

jb

y    1    1





jb jb

y y

y

 Design the single-stub shunt tuning network to match the transmission line,

where



  ^Z   ^{f GHz}

j

Z

 15  10  ,

 50  ,  2

Smith chart

 Fixed length between the load and stub



Smith chart

 Easy calculation of the matching network

 Narrow bandwidth characteristics





 /

0

,

1

 Z Z l 

Z

 Complicated design procedure

 Broad bandwidth characteristics

 The theory of small reflections



 Binomial multisection line

 Chebyshev multisection line

 Tapered line

