Lossless TLine netlist is wrong in some cases

[tomhajjar]

The TLine netlist has unneeded entries confusing ngspice. You can't fix the problem setting a parameter value to "0" or " "

T1 1 2 3 4 Z0=50 Td=1ns -> good - Unfortunately Qucs will add "F=0"/"F=" and "NL=0"/"NL="

T1 1 2 3 4 Z0=50 F=1e9 NL=0.25 -> good - Unfortunately Qucs will add "Td=0"/"Td=" nullifying F and NL

T1 1 2 3 4 Z0=50 F=1e9 -> good - Unfortunately Qucs will add Td and NL nullifying F and NL

T1 1 2 3 4 Z0=50 Td=1ns F=0 NL=0 -> bad - If Td used, F and NL should not be in netlist

T1 1 2 3 4 Z0=50 Td=0 F=1e9 NL=0.25 -> bad - Td=0 will nullify F=1e9 NL=0.25

T1 1 2 3 4 Z0=50 Td=1ns F= NL= -> bad

One solution would be a blank entry would delete the item from the netlist.

Transmission_Line_prj.zip

[dwarning]

The attached patch file will solve the problems in tline parameter handling.
All examples show reasonable results.

Tline.patch.txt

[ra3xdh]

@dwarning Thanks for providing a patch. I have added your path as a part of #610

[dwarning]

@ra3xdh Thank you.
But as mentioned in #601 the patch is only a workaround. qucs-s gui has to work as user of ngspice who take care for the both specification modes of tline: 1. Specify Td (F and Nl omitted) 2. Specify F and Nl (Td is omitted and not(!) given in netlist)

[tomhajjar]

1. Specify Z/Td (F and NL omitted and not(!) given in netlist) ngspice will ignore F/NL anyway
2. Specify Z/F/NL (Td is omitted and not(!) given in netlist)
3. Specify Z/F (Td AND NL is omitted and not(!) given in netlist) and ngspice -> NL=0.25

[tomhajjar]

I revisited my project above and ngspice TLine is now working with ver 24.2.0.