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Homework Help: NEXT and FEXT voltages

  1. Oct 16, 2015 #1
    1. The problem statement, all variables and given/known data
    A transmission line is formed by two identical parallel tracks in a printed
    circuit board, as depicted in FIGURE 5. The line has a length of 50 mm
    and all line terminations are of 70 Ω. The line can be assumed to be
    (a) Use equations (4) and (5) from the lesson 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.

    (b) Sketch the NEXT and FEXT waveforms.

    You may find the following relationship helpful in answering this

    For a lossless line:

    The characteristic impedance is given by

    Zo = squroot(L/C)

    and the velocity of propagation by:

    Vp = 1/squroot(LC)

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

    Note that the Vs voltage at the input to the aggressor conductor is

    Vs = Vin (Rin/(Rin+Zo)

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

    Line inductance 400 nH per m
    Line capacitance 80 pF per m
    Mutual inductance 80 nH per m
    Mutual capacitance 10 pF per m

    2. Relevant equations

    KNE = Vp/4(CmZo+Lm/o)

    VNE = KNE [Vs(t) - Vs(t-2td)]

    VFE = KFE l(δ/δt)[Vs(t-td)]

    KFE = 1/2(CmZo -(Lm/Zo))

    3. The attempt at a solution
    so far I have Zo = 70.71Ω
    Vp = 176776695 m/s#
    KNE = 0.08125

    0.5Vin(t) = Vs(t)

    td = l/Vp =282.8 ps

    which gives
    Vs(t)-Vs(t-2td)=0.5(Vin(t)-Vin(t-565.7 ps))

    from then on I am stuck..

    Any help would be appreciated.
  2. jcsd
  3. Oct 21, 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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