Impedance Matching

Microwave EngineeringMicrowave EngineeringCHO, Yong HeuiCHO, Yong Heui

Microwave Microwave EngineeringEngineering

EM Wave EM Wave LabLab

2

Maximum power transfer

1. Impedance matching

Phase shifter

Condition-

Matching network

Reflection

No reflection-

*

0 )( LZZ

LZZ 0

출처 : KAIST

Microwave Microwave EngineeringEngineering

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Matching with lumped elements

Compact size Difficulties in finding the proper value of L or C L-network, T-network, and -network

1. Impedance matching

Microwave Microwave EngineeringEngineering

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4

Procedure: L-network

Define

Draw

Find to intersect the circle

Draw

Find to cancel out

0/ ZZz LL

LL zy /1

jxzL 1

11 jXjxzin

jB

Lz

jX jx

1. Impedance matching

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Example

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

where

MHzfZjZL 500,100,100200 0

Smith chart

1. Impedance matching

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6

Single-stub matching

Open stub and short stub

Short stub (L)

Open stub (C)

1. Impedance matching

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Single-stub matching

Simple matching network

Smith chart

1. Impedance matching

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Procedure: shunt stub

Define

Draw

Move to the direction of generator

Find the intersection of the circle

Adjust the length of a shunt stub

0/ ZZz LL

LL zy /1

jbyL 1

jbyS 11

jbjb

yyy SLin

1. Impedance matching

Microwave Microwave EngineeringEngineering

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Example

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

where

GHzfZjZL 2,50,1015 0

Smith chart

1. Impedance matching

Microwave Microwave EngineeringEngineering

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10

Double-stub matching

Fixed length between the load and stub

Smith chart

1. Impedance matching

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Quarter-wave transformer

Easy calculation of the matching network Narrow bandwidth characteristics

/,01 lZZZ L

1. Impedance matching

Microwave Microwave EngineeringEngineering

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12

Transitions

Complicated design procedure Broad bandwidth characteristics The theory of small reflections

Binomial multisection line Chebyshev multisection line Tapered line

1. Impedance matching