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Impedance Matching


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Impedance matching is a procedure for obtaining the maximum power transfer to a load. What is a goal for microwave design? If we can give maximum power to a load, we succeed in design. Impedance matching allows us to make that happen.

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Impedance Matching

  1. 1. Antenna Engineering CHO, Yong Heui Impedance Matching
  2. 2. 1. Impedance Matching Basic Concept Voltage or Current -> Ratio is a key factor Load Wave
  3. 3. Maximum power transfer 1. Impedance matching <ul><li>Condition for maximum power transfer </li></ul><ul><li>Matching network </li></ul><ul><ul><li>- Usually source and load are fixed. </li></ul></ul><ul><li>Reflection </li></ul><ul><ul><li>- Conjugate matching doesn’t mean no reflection. </li></ul></ul><ul><li>No reflection </li></ul>
  4. 4. 출처 : KAIST 1. Impedance Matching Variable Phase Shifter
  5. 5. Matching with lumped elements <ul><li>Compact size </li></ul><ul><li>Difficulties in finding the proper value of L or C </li></ul><ul><li>L-network, T-network, and -network </li></ul> 1. Impedance matching
  6. 6. Procedure: L-network <ul><li>Define </li></ul><ul><li>Draw </li></ul><ul><li>Find to intersect the circle </li></ul><ul><li>Draw </li></ul><ul><li>Find to cancel out </li></ul> 1. Impedance matching
  7. 7. Example <ul><li>Design the L section matching network to match the transmission line, </li></ul><ul><li>where </li></ul> Smith chart 1. Impedance matching
  8. 8. Single-stub matching <ul><li>Open stub and short stub </li></ul> Short stub (L) Open stub (C) 1. Impedance matching
  9. 9. Single-stub matching <ul><li>Simple matching network </li></ul> Smith chart 1. Impedance matching
  10. 10. Procedure: shunt stub <ul><li>Define </li></ul><ul><li>Draw </li></ul><ul><li>Move to the direction of generator </li></ul><ul><li>Find the intersection of the circle </li></ul><ul><li>Adjust the length of a shunt stub </li></ul> 1. Impedance matching
  11. 11. Example <ul><li>Design the single-stub shunt tuning network to match the transmission line, </li></ul><ul><li>where </li></ul> Smith chart 1. Impedance matching
  12. 12. Double-stub matching <ul><li>Fixed length between the load and stub </li></ul> Smith chart 1. Impedance matching
  13. 13. Quarter-wave transformer <ul><li>Easy calculation of the matching network </li></ul><ul><li>Narrow bandwidth characteristics </li></ul> 1. Impedance matching
  14. 14. Transitions <ul><li>Complicated design procedure </li></ul><ul><li>Broad bandwidth characteristics </li></ul><ul><li>The theory of small reflections </li></ul> <ul><li>Binomial multisection line </li></ul><ul><li>Chebyshev multisection line </li></ul><ul><li>Tapered line </li></ul> 1. Impedance matching