Dear experts,

Sorry to disturb you again. :)  The following figure explains the case more clearly:

   ________    ________    ________    ________
  |________|  |________|  |________|  |________|
     GND        Signal       GND        Signal

So they are not driven differentially. General tools calculate differential impedance, right? Can just setting the distance to the plane very high get correct result?

Thanks for your help and look forward to your reply.

Cai