FreeLists / si-list / [SI-LIST] hspice simulation with w-element + s model

["Haikun Zhu" <haikun@xxxxxxxxx>]

Hi there,

Thanks for everyone helped me out about the embedded microstrip line
impedance. Now I got this new question of w-element + s model
simulation in hspice.

I'm trying to produce the eye diagram for a differential microstrip
line. The line ports are numbered like this:

1 + ------------------------ + 3
2 + ------------------------ + 4

I exported the 4-port touchstone file from ADS and throw it into
hspice. Here is part of my netlist

*************** netlist snippet start ********************
* Termination
rout1 out1 gnd 22.6
rout2 out2 gnd 22.6

* Input PRBS
vin1 in1 gnd LFSR (0 1 100ps 6.67ps 6.67ps 15G 85 [7,1] rout=3D22)
vin2 in2 gnd LFSR (0 -1 100ps 6.67ps 6.67ps 15G 85 [7,1] rout=3D22)

* The differential pair
w1 in1 in2 gnd out1 out2 gnd smodel=3Ds_model N=3D2 l=3D2cm
+ NODEMAP=3DI1I2O1O2

* s model
.model s_model S TSTONEFILE=3D'mydiffpair.s4p' XLINELENGTH=3D2cm
************* netlist snippet end ****************

Now i constantly get the error message
  **error** (S model: (0:s_model) ) near and far end of the line 0 are
not connected. please check the s-parameters and NODEMAP at 0 Hz

It looks to me that it's the problem of node mapping. However, i tried
different mapping orders and still can not get rid of the problem. I
had no problem for single-ended case, no problem for s-element +
touchstone file for this differential pair.

Thanks in advance!

Haikun
Graduate student
UCSD

--
For every difficult problem there is always
a simple answer and most of them are wrong.
                                           -- Clayton R. Paul
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