Could you suggest me how to select reference impedance (Convert->Renormalize) for an S-Parameter model of a power plane extracted by converting Z-Parameters plot from decoupling analysis?, I am asking this question because when I select reference normalization impedance to be 0.1 Ohm it gives S21 with for e.g.: -40dB and if I select normalization impedance to be 0.01 Ohm it gives S21 for e.g.: -25dB. Why is this difference and how to select suitable normalization impedance for a power plane. I know that normalization impedance for a SE tranmission line is 50Ohms.