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Lec05ek

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wave guides and tranasmission lines

Published in: Engineering
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Lec05ek

  1. 1. EEE194RF_L5 2 Lossless Transmission Line Model • Line representation )( )( 0 CjG LjR Z ω ω + + =Characteristic impedance: Note: R, L, G, C are given per unit length and depend on geometry Lossless implies: R = G = 0!
  2. 2. EEE194RF_L5 3 Transmission Line Parameters for different line types 2-wire coax σδπa 1 ) 2 (1 a D ch− π µ R L G C ) 11 ( 2 1 ba + πσδ parallel-plate ))2/((1 aDch− πσ ))2/((1 aDch− πε σδw 2 w d µ d w σ d w ε )ln( 2 a b π µ )/ln( 2 ab πσ )/ln( 2 ab πε
  3. 3. EEE194RF_L5 4 Microstrip line 1/), 4 8ln( 2 / 00 0 <+= hW h W W h Z effεπ εµ ])/1(04.0)/121[( 2 1 2 1 22/1 hWWhrr eff −++ − + + = −εε ε
  4. 4. EEE194RF_L5 5 What is a voltage reflection coefficient? 0 0 0 ZZ ZZ L L + − =Γ Reflection coefficient at the load location )(10 ∞→=Γ LZ )0(10 →−=Γ LZ
  5. 5. EEE194RF_L5 6 Standing Waves )()( djdj eeVdV ββ −++ −= )2/cos()sin(2),( πωβ += + tdVtdv
  6. 6. EEE194RF_L5 7 Standing wave ratio ||1 ||1 || || || || 0 0 min max min max Γ− Γ+ === I I V V SWR SWR is a measure of mismatch of the load to the line SWR=1 (matched) or SWR ∞→ (total mismatch) match

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