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How does the "Analyze Signal" tool work? What factors does it consider in its calculations?

Message 1 of 4
150 Views, 3 Replies

How does the "Analyze Signal" tool work? What factors does it consider in its calculations?

I'm excited about this tool, but I want to understand exactly what variables it's taking into account. Besides the target impedance/tolerance/frequency from the user input, and obviously the length/shape of the traces, what else does it consider when estimating the impedance range of the path? 

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Message 2 of 4
in reply to: sdossGKZ4Z

Simplest explanation is that it looks at every segment and slices the segments anywhere that the coupling distance (X-Y-Z) changes.  This is done along the conductor path and then uses the cross sections to feed Method of Moment calculations (performed by Ansys on the server side) to compute the reactances at any given point.  This, along with your specified upper/lower bound frequencies, determine the impedance(s) and we overlay that visually while also providing you a tabular view of that along with the individual capacitances, inductances, etc at each 'slice of interest'.  The coupling considers any geometry on the XYZ planes within a "sphere" of sorts, however the values for via cylinders are not there because of the complex non-linearity of the via impedances when a via is single-ended and not surrounded by other vias for matching.  For those cases you would be better to export the EDB file from Fusion and run simulation in SIWave / Ansys-proper and use their via solver.


We communicate to the MoM Solver things like differential pairs, power / ground nets, etc. and we will be adding more capability as we start to get the increased feedback and requests from users.  The aim here is plainly "give the user the ability to think / talk / visualize a design like an EE and not a geometer".  The basic supposition for this was (as an EE / Physicist myself):  why is everything translated to mils or mm when the simple fact is, I want to query what the parasitic capacitance is on the clock line?  The extension addresses this and the continued interest and feedback from users will help us refine the questions so we can deliver real, pragmatic, fast solutions intended to answer them.  For the very bleeding edge use-cases the EDB export gets you into Ansys (ODB++ export on Mac) and that's where the S-Parameter modeling will be the best bet.  Being partnered with Autodesk will hopefully ensure  success at every level.


Hope that helps.


matt - Auotdesk

Message 3 of 4

Sorry - to clarify the question about shape -> we actually take a geometric cross section which ensures we dont worry much about shapes like curves versus straight versus rounded end caps versus is this a circle, etc.  It is best to think of instead like a ray-cast.  From the point of a change in adjacent geometry or the segment under analysis, we ray cast in 3 dimensions and detect the adjacent elements within a coupling distance.  If there is a curve, we sample the curve anywhere the coupling distance changes within a threshold specified by Ansys as best-practice given Ansys' experience with the very high-end simulation.  With the slices we calculate we send that to the MoM solver and get results for each slice.


Hope that helps.


matt - Autodesk

Message 4 of 4

Final addition - all of this was the background behind why we added the layer stackup changes and the materials in the layers dialog match the materials Ansys also has for dielectrics but can be user-modified.  This was a lot of little background stuff we did to prepare for this much larger step but we knew those things would benefit everyone.  


Hope that helps,


matt - Autodesk

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