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Homework Help: NEXT and FEXT Crosstalk

  1. Jun 12, 2015 #1
    1. The problem statement, all variables and given/known data
    For a lossless line:
    The characteristic impedance is given by Zo=sqrt(L/C)

    and the velocity of propagation by Vp =1/(sqrt(L*C))

    where L and C are, respectively, the line's inductance and capacitance per metre length.

    A transmission line is formed by two identical parallel tracks in a printed circuit board, as depicted in the attached FIGURE. The line has a length of 50 mm and all line terminations are of 70 Ohms. The line can be assumed to be lossless.

    a) Use the following equations:

    VNE = KNE[Vs(t) - Vs(t - 2td)]
    KNE = (Vp / 4)[(CM * Zo) + (LM / Zo)]

    VFE = KFE * l * (d / dt)[Vs(t - td)], where l is the length of the line.
    KFE = 1/2[(CM * Zo) - (LM / Zo)]

    to calculate the magnitude of the NEXT and FEXT voltages generated in the victim conductor when the source voltage, Vin, in the aggressor conductor is a voltage step of 2 V with a rise time of 100 ps.

    [Note that the Vs voltage at the input to the aggressor conductor is
    Vs = Vin[Rin / (Rin + Zo)] .]

    CM and LM are, respectively, the mutual capacitance and inductance per metre length.

    [ mentor note: no success adding image inline; so readers must click this thumbnail to see larger image ]


    b) Sketch the NEXT and FEXT waveforms.

    2. Relevant equations

    VNE = KNE[Vs(t) - Vs(t - 2td)]
    KNE = (Vp / 4)[(CM * Zo) + (LM / Zo)]

    VFE = KFE * l * (d / dt)[Vs(t - td)]
    KFE = (1 / 2)[(CM * Zo) - (LM / Zo)]

    3. The attempt at a solution

    Calculate for Zo and Vp

    Zo = 70.71

    Vp =176776695.3

    Then plug in numbers to find KNE

    KNE = 3124970032 ( number looks massive not sure if it's right)

    Getting stuck on finding VNE

    Not sure if t = rise time. Is Vin = 2? How do I find td?

    Thanks for your help in advance.

    [ mentor note: excessive bold text corrected ]
    Last edited by a moderator: Jun 13, 2015
  2. jcsd
  3. Jun 18, 2015 #2
    Thanks for the post! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?
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