Hello,

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.

Regards,

Ravi

Hi Ravi,

Either one will work fine as the simulator will know from the Touchstone file what was the value of the reference impedance. Accordingly to the Touchstone spec 11, pages 4 and 5, the data file must contain an option line formatted as follows:

# <

frequency unit> <parameter> <format> R <n>R

nspecifies the reference resistance in ohms, where n is a positive number of ohms (the real impedance to which the parameters are normalized). The default reference resistance is 50 ohms.Here is an example from a PDN Z-parameter extracted using HyperLynx:

-----------------------------------------------------------------

! HyperLynx V8.1-64 SI-SPICE V2010.06.16

# HZ Z RI R 1.000000e-001

----------------------------------------------------------------

Cheers,

Cristian