[SI-LIST] obtaning diff param in HSPICE

Hi everyone,
I have the following question I have a 2 conductor trasmission line in
HSPICE given with the following syntax

W 1 3 0 2 4 0 N=2 L=10e-3 RLGCMODEL=xxx

I'm using the following statement to simulate the S-parameter data

P1 1  0  port=1 AC 1 z0=50
P2 2  0  port=2 AC 1 z0=50
P3 3  0  port=3 AC 1 z0=50
P4 4  0  port=4 AC 1 z0=50

Once I obtain the S-parameter data I convert them into diff - Smm =
M*Sstinv(M) where M is = 1/srt(2) [ 1 0 -1 0 ; 0 1 0 -1 ;1 0 1 0 ; 0 1 0 1
].

No lets say I make the following changes
P1 1 3  port=1 AC 1 z0=100
P2 2 4  port=2 AC 1 z0=100

S11 S12 S21 and S22 should be coincident to Smm11 Smm12 Smm21 Smm22 from
above

Let's say now I make these other changes
W 1 1 0 2 2 0 N=2 L=10e-3 RLGCMODEL=xxx
P1 1 0  port=1 AC 1 z0=25
P2 2 0  port=2 AC 1 z0=25

S11 S12 S21 and S22 should be coincident to Smm33 Smm34 Smm43 Smm44 from
above


Does anybody see any flaws in the above reasoning ?

-JS-


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