1. Prof. David R. Jackson Dept. of ECE Notes 3 ECE 5317-6351 Microwave Engineering Fall 2011 Smith Chart Examples 1

2. Find Z(-d) Example 1 a 2 Impedance chart

3. b c Example 1 (cont.) 3

4. Find Y(-d) Example 2 a 4 Admittance chart

5. Example 2 (cont.) b c 5 Admittance chart

6. Simple answer: * When adding elements in series use Z -chart * When adding elements in parallel use Y -chart Which Chart to Use? 6

7.  Use reactively loaded section of transmission line. most common to use open or short load Non-absorbing load ( R L = 0 ) Using Reactive Loads 7 Impedance chart Reactance

8. Susceptance Using Reactive Loads (cont.) 8 Admittance chart

9. Use a short-circuited section of air-filled TEM, 50  transmission line (  = k 0, g = 0 ) to create an impedance of Z in = -j25  at f = 10 GHz. Example 3 L = 1.28 cm 9 Impedance chart

10. Use an open circuited section of 75  ( Y 0 = 1/75 S ) air-filled transmission line at f = 10 GHz to create an admittance of Example 4 10 Admittance chart

11. Note: At d we have Want to pick d and Y s such that Y in = Y 0. Matching Circuit 11 Admittance chart

12. We want Choose Matching Circuit (cont.) 12 Admittance chart

13. Example 5 ZLZL Z0Z0 lsls Z0sZ0s d 13 In this example we will use the “usual” Smith chart, but as an admittance calculator.

14. Example 5 (cont.) X X X wavelengths toward load wavelengths toward generator Smith chart scale: Admittance calculator 14  plane SC OC (We’ll use the first choice.)

15. Example 5 (cont.) X Admittance calculator From the Smith chart: Analytically: 15

16. Quarter-Wave Transformer At f 0 : For  in = 0 16

17. Match 100  load to 50  transmission Line at f 0. Example 6 17