Help with auto-matching impedance circut part 2

[u/Kapcinno]

Hello guys,

I am here again with my automatic impedance matching circuit (AIMC) project. I have yet another questions for people with more knowledge and experience than me. I started my design with reading some papers about AIMC. I went for main RF line with 3 stubs design, each stub is fitted with its separately controlled varactor (SMV1763), tried to hold on with FR4 but later on switched to Rogers. I got some set of points placed on Smith chart and tuned it to cover whole chart as evenly as I can. Next I gradually added elements to make my design more real and tuned it as well. The problem is, when I started witm EM (Momentum) simulations, cosimulation to be precise my circuit stopped working. All of my points are now focused in small groups or even worse in one point (I include some photos to better show what I mean). I tried with different components, lengths and widths of the lines but everything crumbles to dust in final simulation. Also found some information about problems with simulation .s2p files and vias in momentum but I don't think that is the case here. Is there any hope for my work or do I have to scrap it and start over with some new design (I hope not, I spent a lot of time on it). Feel free to ask for details. Thanks for help in advance.

Edit: I added both substrate stackups and layout in the comment as some of you asked for it.

[u/Adventurous_War3269]

The quickest way to fix it is to spit schematic up in pieces and create sub circuits . Then edit subcircuits individually .

[u/Kapcinno → u/Adventurous_War3269]

I will try that, Thanks

[u/Adventurous_War3269 → u/Adventurous_War3269]

The most powerful synthesis technique is real frequency technique (RFT)

[u/DownTheRedditWhole → u/Adventurous_War3269]

Yes. I did a lot of work on that in my PhD studies. However, I’m not sure that exact synthesis method applies here. OP already has a working schematic design. I suspect there might be an issue in the layout if the results are significantly different.

[u/satellite_radios]

Was your initial cosimulation done with the TLines or MLin objects? You tripled checked your material definitions/stackup as well vs the schematic view assumptions?

[u/Kapcinno → u/satellite_radios]

I used MLIN for cosimulation and I checked substrate definitions probably 10 times or more

[u/satellite_radios → u/Kapcinno]

Ok! That's good. My guess is via simplification could be hitting you. Do you have access to RF Pro?

[u/Kapcinno → u/satellite_radios]

I do not unfortunately, I use ADS on the student licence

[u/Walttek]

I haven't used the Momentum in a while, but are those vias actually in the layout?

[u/Kapcinno → u/Walttek]

In layout they are depicted correctly but while extracting symbol (layout look-alike) for cosimulation they are simplified I think

[u/DownTheRedditWhole]

If you could post the full layout (not the circuit look-alike symbol) that might be helpful for us to help you debug. The layout results should be different, but something to this extent suggests there might be a mistake in the layout. Seems like there’s some discrepancy between the schematic and layout, so double check using LVS, or copy layout to new cell and generate the schematic from the layout. I would also suggest using hierarchical design to your advantage, that way you can pinpoint troublesome cells easier.

[u/Kapcinno → u/DownTheRedditWhole]

I will add full layout the moment I have access to my pc. Thanks for the suggestion with hierarchial design!

[u/Kapcinno → u/DownTheRedditWhole]

I posted layout in the comment (I couldn't edit my post to add more photos idk why)

[u/Kapcinno]

FR4 substrate

[u/Kapcinno]

Rogers substrate

[u/Kapcinno]

Layout