Home Forums Usage Need help with s-par simulation

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      Hi, I am trying to simulate s2p model using a template sch provided with “simulation_SParameter.qucs” from examples webpage. From the template I deleted all components. I have only input port, s2p file, output port. The simulation is configured as 1-5GHz with 5 point and noise sim enabled.

      As an s2p model I use BFU725F_2V_5mA_S_N.s2p downloaded from NXP website.

      Problem nr 1: the simulation fails with the model file BFU725F_2V_5mA_S_N.s2p. However the simulation runs fine when I remove the noise data from the file. The simulation is also fine when I use any other s2p file from the BFU725F package without the noise data. Why?

      Problem nr 2: Of course without the noise data in the file I cannot simulate NF, NFmin.

      Problem nr 3: I plot gain circles on a Smith chart using a function GaCircle(200).  What does (200) mean in this plot? Also, On the graph with gain circles, bottom left corner, there is a number showing most of the time 2.7 in this case. What does it mean?


      • This topic was modified 10 months, 2 weeks ago by stan3c.

        Can you attach the project you are working on?


          Problem nr 1 is indeed a bug. Thanks a lot for reporting it!

          Concerning problem nr 3: GaCircle(200) means plot the circle for power gain = 200. The number in the bottom left corner of a smith chart appears if the data is outside the unity circle and gives the outer radius of the chart.


            Schematic and s2p model file attached.

            • This reply was modified 9 months, 2 weeks ago by stan3c.

              Hi !

              I tried your file, if you reduce the number of entries in the noise-data it will run. I reduced nosie-data to 16 rows , dont know where the limit is.

              The original BFU725 s2p file contains more noise-data rows than  “normal”

              /Hannes – SM6PGP


                Indeed, deleting some of the noise data helps.

                But I do not think it is about the number of rows. It looks more like it does not like some of the data in some of the rows. With some data the simulator finishes with “success” message, but returns no data, no gain graph, no s11, s22 graph data.

                Ok, it is a bug.

                • This reply was modified 9 months, 2 weeks ago by stan3c.
                • This reply was modified 9 months, 2 weeks ago by stan3c.

                  Hi All,

                  I am also intrested in sNp with more than 40 ports simulation.

                  Is this possible ?



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