Strategy to color crosstalk source

[Baluncore]

Why in differential lines Fext is acting by pulses but NEXT is by steps.

For the transmitted wave, the aggressor forward energy of a step, that couples into the victim track, flows forwards with the aggressor step, and so accumulates at only one point in the time record. The cross-talk is seen as a single big integrated pulse at the far-end.

For the reflected crosstalk, each short element of crosstalk, has a different distance to propagate during its return to the input. For that reason, all the adjacent small pulses arrive at the input over twice the transit time, which forms a long low step.

 

[yefj]

Hello Baluncore, this is very intresting ,regarding the NEXT.
When we have sudden rise in voltage it couples as sudden rise of voltage on the victim because parasitic capacitance I=CdV/dt and has to keep the same amout of voltage on both ends.
Two question:
1.the coupling agression creates cross talk wave both in the direction of propogation of the agressor and in the oppsoite direction .the crosstolk waves are continues and traveling as the agressor edge traveling,Why on one end the crosstalk is pulses whhile in the other its contues steps?

2.In the far end both the agressor step and the victim cross talk arrive why the victim pulses gets "integrated"
What is the physical logic in that?
Why its not seeing things like the FEXT that sees pulses arrive individually at each time point?
Thanks.

 

[Baluncore]

1.why this coupled energy exibits as pulse, its not a pulse its a parasitic traveling wave going in the direction as the agressor step.where am I wrong?

Only the step changes in the aggressor crosstalk into the victim. That is because the capacitive coupling is low, and the signal voltage step involves a current step that couples inductively into the victim. That pulse is energy of the step.

2.In the far end both the agressor step and the victim cross tal arrive why the victim pulses gets "integrated"
What is the physical logic in that?

Since the aggressor step velocity is the same as the victim pulse velocity, the crosstalk is accumulated at one point in the signal time.

 

[yefj]

Hello Baluncore,I have am trying to visualise this situation using a simpler case in another article shown below.
As you can see in the photo taken from the article the Vb and VF pulses are a result of odd mode and even mode being not in the same velocity .
why exactly the pulse shape is because of that?
Thanks.