Electronics > RF, Microwave, Ham Radio



Is there any free (as in free-beer-free, not intending to get into an open source licence discussion) or inexpensive software that can do an EM co-simulation with S-parameter models of active devices?

I know this is possible in ADS and Microwave Office but these class as very expensive.  Old versions would have been fine but I don't think they are available.  I'm not a student, nor am I working in the field professionally.

Qucs-Studio can do S-param simulations (quite well, just has a few UI instabilities) and it can also do FDTD EM simulation of passive networks, but unless I'm missing something I cannot include the linear model of an active device in an EM co-simulation which would be useful when tweaking the shapes of microstrips.


It's a while since I last used Sonnet Lite, but I think it allows up to 6 ports. If so, it might be possible to place ports where the (temporarily missing) active device connects to.
If Qucs can support up to 6 port s-parameters then you could simulate the PCB layout in Sonnet Lite and then export it as an n port device to use in Qucs and simply attach the s-parameter model for the active device to the relevant ports and simulate using a linear simulator in Qucs.

I've been using the full version of Sonnet to do similar things with the Genesys simulation suite since about 2004. Genesys can support the Sonnet engine and it first allowed this about 20 years ago.


It is very expensive but effectively does what you are asking. However, it might also be possible to achieve the same thing using Sonnet Lite and Qucs. It won't be as seamless, but it might work? I suspect that there may be a limitation in Sonnet Lite that will scupper this but it might be worth a try.

Qucs  0.0.20 here ( not Qucs-S because I can't get it working on Fedora)

I just added the generic op amp (G=10^6)  to an existing model in S params solver  of a 50 Ohm  passive attenuator.

It complains   .. no DC..  so it is necessary to call in the DC solver, then the S param seems to solve OK.

I tried playing with Sonnet Lite v18 today to see what is allowed in the Lite version. It does allow several ports but unfortunately, it only seems to allow ports at the edges of the box. I tried adding internal ports to shapes inside the box area and it gave me a message box that said this wasn't possible in the Lite version.

See below for an old interdigital filter design that covers the GPS band. This imported into Sonnet Lite just fine and it simulated in about 6 seconds. This uses Rogers 4003C PCB material that is 0.032" thick. This design required 22Mb memory in Sonnet Lite. I think the upper limit for the Lite version is 64Mb and this is quite generous.

I set Sonnet up to export the results as an s-parameter file (filename = GPS3s2p.txt) and I've attached this s parameter file below. Sadly, this isn't quite what Alan was requesting, but Sonnet Lite can export s-parameter data that can be used in other simulators like Qucs.

So the only way this could work would be to simulate each (filter?) section in Sonnet and then export s-parameter files of the filter and then import them into Qucs where they could be connected to s-parameter data for active devices.

The full version of Sonnet allows internal ports and it's a shame the Lite version doesn't allow a few internal ports.

That's a shame indeed.  I've been pretty impressed by Sonnet Lite simulation of my filters and Qucs Studio does support general n-ports from touchstone files. You can it seems add "via" ports in Sonnet Lite but not proper de-embedded co-calibrated ports as that needs one of the commercial versions.



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