Hi, Jayleung:
Two z-parameters are defined in IE3D. The z-parameters are the standard z-parameters. Some users want to find Zsp(i,j)=Sqrt(Zci*Zcj)*[1+S(i,j)]/[1-S(i,j)] and we define Zsp(i,j) as Z for s-parameters. It is not defined else. They are just defined in IE3D to meet some customers' need. Please note that Z(1,1) = Zsp(1,1) for a 1-port structure. However, for a multiple port structure, Z(i,j) is not equal to Zsp(i,j) for any i and j combination.
Best regards