Reply To: S-parameter causality issue

[Dan Dvorscak]

Its not directly related to causality, but numerics can play a part in it, but you've got way more points in your decade sweep than I would normally use. Also, I would stop the decade sweep at 10MHz.

My usuall set up is two sweep. 

• A 10MHz linear step sweep starting at 0 Hz (so you don't need a separate line just for the DC point) going up to the max frequency.
• Then a 10 points per decade sweep from 100 Hz (Though that depends on the application. If it is a PDN, then I might start at 1 Hz to be safe.) to 10MHz. 

One more thing to double check, if you are using external s-parameter models for components, you should also run a causality test on those.