Hi Element7k,
thanx a lot. that really helps. i chose electric boundary for Zmin and that was the mistake. now i got the line impedance calculated.
but now i m having a problem in farfield. the solver said that some PEC material touches the boundary which can lead to inaccurate farfield result. the thing is i didn't even define any PEC material in my structure. ( i chose open boundary for all but for Zmax i put open boundary add space- because of the farfield).
(i wanted to attach my model, but the file mod is not allowed here)