impedance matching

Impedance Matching

Antenna Antenna EngineeringEngineering

CHO, Yong HeuiCHO, Yong Heui


EM Wave LabEM Wave Lab2

1. Impedance Matching

Basic Concept

Voltage or Current → Ratio is a key factor

LoadWave



Maximum power transfer

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 )( LZZ

LZZ 0



출처 : KAIST

1. Impedance Matching

Variable Phase Shifter



Matching with lumped elements

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




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




Example

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

where

MHzfZjZL 500,100,100200 0

Smith chart




Single-stub matching

Open stub and short stub

Short stub (L)

Open stub (C)




Single-stub matching

Simple matching network

Smith chart




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




Example

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

where

GHzfZjZL 2,50,1015 0

Smith chart




Double-stub matching

Fixed length between the load and stub

Smith chart




Quarter-wave transformer

Easy calculation of the matching network Narrow bandwidth characteristics

4/,01 lZZZ L




Transitions

Complicated design procedure Broad bandwidth characteristics The theory of small reflections

Binomial multisection line Chebyshev multisection line Tapered line


impedance matching

Technology

yong heui impedance

shunt stub

short stub short stub

stub smith chart

open stub c

transmission line

circle draw findto

fixed length