Impedance Matching

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Impedance Matching

  1. 1. Impedance Matching Microwave Engineering CHO, Yong Heui
  2. 2. Microwave Engineering1. Impedance matching Maximum power transfer 출처 : KAIST  Condition - Z 0 = ( Z L )*  Matching network  Reflection  No reflection - Z0 = Z L Phase shifter 2 EM Wave Lab
  3. 3. Microwave Engineering1. Impedance matching Matching with lumped elements  Compact size  Difficulties in finding the proper value of L or C  L-network, T-network, and Π-network 3 EM Wave Lab
  4. 4. Microwave Engineering1. Impedance matching Procedure: L-network  Define zL = Z L / Z0  Draw yL = 1 / zL  Find jB to intersect the circle z L = 1 + jx  Draw zL  Find jX to cancel out jx zin = 1 + jx + jX = 1 4 EM Wave Lab
  5. 5. Microwave Engineering1. Impedance matching Example  Design the L section matching network to match the transmission line, where Z L = 200 − j100[ Ω], Z 0 = 100[ Ω], f = 500 MHz Smith chart 5 EM Wave Lab
  6. 6. Microwave Engineering1. Impedance matching Single-stub matching  Open stub and short stub Short stub (L) Open stub (C) 6 EM Wave Lab
  7. 7. Microwave Engineering1. Impedance matching Single-stub matching  Simple matching network Smith chart 7 EM Wave Lab
  8. 8. Microwave Engineering1. Impedance matching Procedure: shunt stub  Define zL = Z L / Z0  Draw yL = 1 / zL  Move to the direction of generator  Find the intersection of the circle y L = 1 + jb yin = y L + y S  Adjust the length of a shunt = 1 + jb − jb = 1 stub y S = − jb 8 EM Wave Lab
  9. 9. Microwave Engineering1. Impedance matching Example  Design the single-stub shunt tuning network to match the transmission line, where Z L = 15 + j10[ Ω], Z 0 = 50[ Ω], f = 2GHz Smith chart 9 EM Wave Lab
  10. 10. Microwave Engineering1. Impedance matching Double-stub matching  Fixed length between the load and stub Smith chart 10 EM Wave Lab
  11. 11. Microwave Engineering1. Impedance matching Quarter-wave transformer  Easy calculation of the matching network  Narrow bandwidth characteristics Z1 = Z 0 Z L , l = λ / π 11 EM Wave Lab
  12. 12. Microwave Engineering1. Impedance matching Transitions  Complicated design procedure  Broad bandwidth characteristics  The theory of small reflections  Binomial multisection line  Chebyshev multisection line  Tapered line 12 EM Wave Lab

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