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ECE 598 JS Lecture - 05 Coupled Lines

ECE 598 JS Lecture - 05 Coupled Lines. Spring 2012. Jose E. Schutt-Aine Electrical & Computer Engineering University of Illinois jesa@illinois.edu. Crosstalk Noise. Signal Integrity. Crosstalk Dispersion Attenuation Reflection Distortion Loss Delta I Noise Ground Bounce Radiation.

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ECE 598 JS Lecture - 05 Coupled Lines

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  1. ECE 598 JS Lecture - 05 Coupled Lines Spring 2012 Jose E. Schutt-Aine Electrical & Computer Engineering University of Illinois jesa@illinois.edu

  2. Crosstalk Noise Signal Integrity Crosstalk Dispersion Attenuation Reflection Distortion Loss Delta I Noise Ground Bounce Radiation

  3. TEM PROPAGATION

  4. Telegrapher’s Equations L: Inductance per unit length. C: Capacitance per unit length.

  5. Crosstalk noise depends on termination

  6. Crosstalk depends on signal rise time tr = 1 ns tr = 7 ns

  7. Crosstalk depends on signal rise time tr = 1 ns tr = 7 ns

  8. Coupled Transmission Lines

  9. Telegraphers Equations for Coupled Transmission Lines Maxwellian Form

  10. Telegraphers Equations for Coupled Transmission Lines Physical form

  11. Relations Between Physical and Maxwellian Parameters (symmetric lines) L11 = L22 = Ls L12 = L21 = Lm C11 = C22 = Cs+Cm C12 = C21 = - Cm

  12. Even Mode Add voltage and current equations Ve : Even mode voltage Ie : Even mode current Impedance velocity

  13. Odd Mode Subtract voltage and current equations Vd : Odd mode voltage Id : Odd mode current Impedance velocity

  14. Mode Excitation

  15. PHYSICAL SIGNIFICANCE OF EVEN- AND ODD-MODE IMPEDANCES * Ze and Zd are the wave resistance seen by the even and odd mode travelling signals respectively. * The impedance of each line is no longer described by a single characteristic impedance; instead, we have

  16. Definitions Even-Mode Impedance: Ze Impedance seen by wave propagating through the coupled-line system when excitation is symmetric (1, 1). Odd-Mode Impedance: Zd Impedance seen by wave propagating through the coupled-line system when excitation is anti-symmetric (1, -1). Common-Mode Impedance: Zc = 0.5Ze Impedance seen by a pair of line and a common return by a common signal. Differential Impedance: Zdiff = 2Zd Impedance seen across a pair of lines by differential mode signal.

  17. EVEN AND ODD-MODE IMPEDANCES Z11, Z22 : Self Impedances Z12, Z21 : Mutual Impedances For symmetrical lines, Z11 = Z22 and Z12 = Z21

  18. Coupled Lines Modal Space Line Space

  19. EXAMPLE (Microstrip) Single Line Dielectric height = 6 mils Width = 8 mils er = 4.3 Zs = 56.4 W Coupled Lines Height = 6 mils Width = 8 mils Spacing = 12 mils er = 4.3 Ze = 68.1 W Zd = 40.8 W Z11 = 54.4 W Z12 = 13.6 W

  20. Even Mode

  21. Odd Mode

  22. EXTRACT INDUCTANCE AND CAPACITANCE COEFFICIENTS

  23. Measured even-mode impedance

  24. Measured odd-mode impedance

  25. Measured even-mode velocity

  26. Measured odd-mode velocity

  27. Measured mutual inductance

  28. Measured mutual capacitance

  29. Even & Odd Mode Impedances

  30. Modal Velocities in Stripline and Microstrip Microstrip : Inhomogeneous structure, odd and even-mode velocities must have different values. Stripline : Homogeneous configuration, odd and even-mode velocities have approximately the same values.

  31. Microstrip vs Stripline Microstrip (h =8 mils) w = 8 mils er = 4.32 Ls = 377 nH/m Cs = 82 pF/m Lm = 131 nH/m Cm = 23 pF/m ve = 0.155 m/ns vd = 0.178 m/ns Stripline (h =16 mils) w = 8 mils er = 4.32 Ls = 466 nH/m Cs = 86 pF/m Lm = 109 nH/m Cm = 26 pF/m ve = 0.142 m/ns vd = 0.142 m/ns

  32. Microstrip vs Stripline Probe Sense line response at near end

  33. General Solution for Voltages

  34. General Solution for Currents

  35. Coupling of Modes (asymmetric load)

  36. Coupling of Modes (symmetric load)

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