Help with NEXT and FEXT volatage magnitudes

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The discussion focuses on calculating the NEXT (Near End Crosstalk) and FEXT (Far End Crosstalk) voltages in a transmission line formed by parallel tracks on a printed circuit board. The parameters include a 50 mm line length, 70 Ω terminations, and a 2 V voltage step with a 100 ps rise time. Key equations for voltage calculations are provided, but participants express confusion regarding the time variables t and td in relation to the rise time. Clarifications on the definitions of NEXT and FEXT, as well as references to additional resources, are shared to aid understanding. The conversation emphasizes the need for accurate definitions and parameters to successfully compute the crosstalk voltages.
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Homework Statement


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

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.

Homework Equations


Vs = Vin x Rin/(Rin+Zo)
Kne =Vp/4 (CmZo + Lm/Zo)
Vne = Kne (Vs(t) - Vs(t-2td)
Kfe = 1/2(CmZo - Lm/Zo)
Vfe = Kfe x length (d/dt)[Vs(t-td)]

The Attempt at a Solution


Zo = root L/C = 70.7Ohms
Vp = 1/root LC = 17677695
Vs = Vin x Rin/(Rin+Zo) = 0.995v
Kne =Vp/4 (CmZo + Lm/Zo) = 0.08

I start to struggle with the next part (assuming the previous are correct) in regard to t and 2td. I'm sure from my notes t=vp but I'm unable to find the page any more and so I'm unable to verify this.

Vne = Kne (Vs(t) - Vs(t-2td) = 0.08

Again I'm struggling to find d and dt in regard to Far end

Kfe = 1/2(CmZo - Lm/Zo) = 3.99515E9

Vfe = Kfe x length (d/dt)[Vs(t-td)]

Any help would be much appreciated.
 
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How many transmission lines do you have?
One line made from two parallel tracks, fed with a differential signal, or;
Two lines over a ground plane that work as a backward wave coupler?
All voltages are differential. What is/are the reference voltage(s).
FEXT = Far end cross talk, from what to what, relative to what?
NEXT = Near end cross talk, from what to what, relative to what?
 
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upload_2018-6-7_21-47-33.png


The above picture accompanied the original question this is all the information I've been given.
 

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You sir are a gentleman and a scholar, thank you very much!
 
is t the rise time? 100ps?

I am thinking not, because later in the notes it expresses td to be half the rise time.

If so what is t? for both the NEXT and FEXT equations??

thanks
Craig
 
is it this:

t = length √LV
td = Tr / 2
 

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