1 / 49

Smith chart

Smith chart. -z. Z c. Z L. z = 0. impedance along the line. Look at a distance z = - L toward the generator. -z. Z c. Z L. z = 0. impedance along the line. impedance is periodic every half-wavelength. -z. Z c. Z L. z = 0. impedance along the line. quarter wavelength.

mandar
Download Presentation

Smith chart

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Smith chart

  2. -z Zc ZL z = 0 impedance along the line Look at a distance z = - L toward the generator

  3. -z Zc ZL z = 0 impedance along the line impedance is periodic every half-wavelength

  4. -z Zc ZL z = 0 impedance along the line quarter wavelength Z <==> Y short ==> open open ==> short

  5. -z quarter wave transformer Zc1 Zc2 ZL z = 0 matching frequency sensitive

  6. -z Zc ZL z = 0 shorted line open line all values of reactance

  7. L X = Zc tan kL

  8. Should I add something in series or in parallel?

  9. series parallel good bad

  10. -z -z -z Zc Zc Zc ZL ZL ZL z = 0 z = 0 z = 0 Eureka! Use a stub.

  11. -z impedance along the line Zc ZL z = 0 shorted line all values of susceptance

  12.  2 1.5 1 My VSWR is 1.25! Zc ZL z = 0 -z

  13. VSWR

  14. -z -z -z Not matched! Zc Zc Zc ZL ZL ZL z = 0 z = 0 z = 0 Needs some -jB somewhere, but where? Eureka! Use a stub, somewhere. How long should it be?

  15. An article appeared in the January, 1939 issue of Electronics that changed forever the way radio engineers think about transmission lines. Phil Smith [1907-1985] devised an extraordinarily clever circular chart that revealed graphically the complex impedance anywhere along a line. No math and minimum fuss. There's a marvelous symmetry in its design - everything fits together neatly. So ingenious was his invention that it has been the standard of the industry - for over sixty years.

  16. -z Zc ZL z = 0 multiply numerator and denominator by the complex conjugate

  17. -z Zc ZL z = 0 equate real and imaginary parts

  18. -z Zc ZL z = 0 real

  19. -z Zc ZL z = 0 real

  20. -z Zc ZL z = 0 imaginary

  21. r b a Equation of circle (x - a)2 + (y - b)2 = r2 y x

  22. clf; clear; plot([-1 1], [0 0], ’y’) axis equal axis off hold on

  23. for r = [0 .2 .5 1 2 5] rr = 1 / (r + 1); cr = 1 - rr; tr = 2 * pi * (0 : .01: 1); plot(cr + rr * cos (tr), rr * sin (tr), ‘y’); end

  24. Ri Rr = 1 Rr

  25. for x = [.2 .5 1 2 5] rx = 1 / x; cx = rx; tx = 2 * pi * (0 : .01: 1); plot(1 - rx * sin (tx), cx - rx * cos (tx), ‘y’); plot(1 - rx * sin (tx),- cx + rx * cos (tx), ‘y’); end

  26. Ri Rr = 1 Rr

  27. for x = [.2 .5 1 2 5] rx = 1 / x; cx = rx; tx = 2 * atan(x) * (0 : .01: 1); plot(1 - rx * sin (tx), cx - rx * cos (tx), ‘y’); plot(1 - rx * sin (tx),- cx + rx * cos (tx), ‘y’); end

  28. Ri Rr = 1 Rr

  29. Ri Rr = 1 Rr reflection coefficient = constant

  30. To generator To load

  31. 1 |R| 0

  32. radius = 0 means no reflection!

  33. z = 0.5 - j0.5

  34. z=j1

  35. Movie to illustrate the frequency dependence of the impedance of a series resonant circuit

  36. Movie to illustrate the frequency dependence of the impedance of a parallel resonant circuit

  37. Movie to illustrate the transformation of a load impedance at various locations on the transmission line l/2

  38. Movie to illustrate the transformation of an impedance to an admittance

  39. y =  z = 0

  40. Zin = ? Zc = 50 W l/8

  41. z = j1 z = 0

  42. Zin = ? Zc = 50 W l/8

  43. Zin = ? Zc = 100 W 0.434 l

  44. z = 0.7 + j1.2 zL = 2.6 + j1.8

  45. Zin = ? Zc = 100 W 0.434 l

  46. Single stub matching

  47. y = 1 + j1 y = 1 - j1 yL = 2 + j1

  48. y = + j1 y = - j1 yL = 

More Related