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 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu