Saturday, August 11, 2018

Transmission Line modeling:  Micro-Cap v12:

So now when I set model type  to lossy I see different simulation results:

Parameters: R=96.7ohms/in  C=1.09pF/in  L=21.217nH/in Len=29.5mm/25.4(mm/in)  = 1.16 in.

It appears that model type ideal does not include parameter  Len.  However since my length of 29.5mm is close to an inch (1.16 inch) I was getting results that seemed reasonable.  However the addition of loss or line resistance I have a dampening and attenuation affect.

Again I have stepped R1 (termination resistor) from 50 ohms to 300 ohms.

If I set model type to Ideal  and change parameters as follows:

Zo = 139 ohms   Td = 152 ps/in * 1.16 in = 176.32ps 

So as you can see from the two plots, the difference is the dampening /attenuation of the signal at the far-end and less noticeably at the near-end.  Far-end is red and near-end is green.  What is similar in both simulations (lossy vs. ideal) is the timing; they seem roughly the same.

And .... lossy model w/ no termination:

I have just added a line indicating the timing at 1.5v * 90%  =  1.35v.  Since it is unclear to me where a clock edge would be located this is just for reference.   More on this when I consider timing.  For now I think I will remove termination resistors.

Comments are welcome:

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