S-Parameter ngspice plot

[dwarning]

I try to make a s-parameter simulation with one point at different operating points:

The problem is that can't plot the results vs Vbe. The result file bjt_spar.dat.ngspice has reasonable values. But plot is nothing. Plot over frequency in sweep works ell.

Can some help me please.

bjt_spar.sch.txt

[tomhajjar]

This may be the issue...

Qucs-S has issues plotting single frequencies, CW. In #156 Vadim used a 3D plot for a temporary fix.

Qucs/ngspice use different methods to calculate simulation frequencies from Start, Stop, Step and Number. One has to play around with the Qucs simulation settings to get the exact frequencies in ngspice. Vadim can explain better than I.

S-parameters_ngspice_prj.zip

[tomhajjar]

I found an old QucsStudio schematic from an ST presentation that looks like your schematic. Forgot where I found it.

Verilog Compiled_Library_prj.zip

[ra3xdh]

@dwarning It is a known issue and explained in #156 and #161 The plotting engine cannot assemble a set of 1x1 plots in a smooth curve. Two solutions are possible:

• Set line style to Circles/Stars in the diagram properties. You will see the simulation points. Also you may use the table.
• Use the scripting simulation to assemble a vector from set of 1x1 plots. I have uploaded a CV-curve simulation example that uses this approach. See Strange behavior trying to simulate Varactor #156 for more info.