EEE 161

Applied Electromagnetics

Laboratory Exercise 5

Lumped Element Impedance Matching

Problem: Match given load impedance to a 50-Ohm line using following methods. Please note that all students will have different points. Since you will submit your group work, all students will submit their work in one file. Each student will do Smith Chart on-paper matching and ADS matching.

Method1.UsingSmith Chart on paper.Print out a color Z-Y Smith Chart. Find the given impedance on the Smith Chart, then find at least one impedance matching circuit.

Method2. Using ADS

  1. Place two ports on the schematic diagram. Change the impedance of port 2 to your given load impedance. Leave port 1 to be 50-Ohms port. Connect two ports with wire. Add an S-parameter block, select sweep type to be single point.
  2. Simulate the circuit you made in step 1.
  3. Data window should automatically open. Place S(1,1) on the Smith Chart in data window.
  4. Verify that the impedance is at the same point on the Smith Chart as you had in Method 1. Left click on the Smith Chart and select Item Options. Select the tab plot options. Select coordinate Both. Increase the line thickness of both impedance and admittance circles by selecting Grid and increasing line thickness.
  5. Copy and paste both ports. Ports should change the numbers to 3 and 4 automatically. Connect a circuit element (either capacitor or inductor) in either series or parallel. Reconnect the element to the other port (and/or ground).
  6. Simulate the circuit. Add the reflection coefficient S(4,4) (4 stands for the port number that has 50-Ohm impedance, not the load impedance port).
  7. Select fork from the top menu. Click on the value of the inductor capacitor, e.g. L=1nH. The sliding ruler will appear. Set the maximum value for the inductance/capacitance to a very large value, say 1000. Click on up or down arrows. If the blue dot (S(4,4)) moves just a little bit, change the step to 10. Move the dot towards either R=1 or G=1 line. If you did not choose the right circuit element or correct series or parallel connection, the dot may not move towards either R=1 or G=1 circles. In that case change either the element or the connection type. Once you managed to place the S(4,4) (blue dot) on the R=1 or G=1 circle go to the next step.
  8. Click update schematics and close the tuning fork.
  9. Copy and paste both ports together with the circuit element you worked on in step 7. Ports should change number automatically to 5 and 6. Add a new circuit element. Usually if the first circuit element was in series the second one will be in parallel. Repeat step 7. When you place the pink dot in the center of the Smith Chart stop.
  10. Click update schematics and close the tuning fork.
  11. Your circuit and the Smith Chart should look like the ones below: