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Finite element Transient Signal Analysis

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Mechatrommer:

--- Quote from: T3sl4co1l on April 20, 2020, 03:23:55 am ---but your screenshot shows floating copper, which will couple to the trace on different sides.  So, a whole bunch of transmission lines are going on there already, plus finer details we can't model so easily with just a few transmission lines.
--- End quote ---
if you are refering to my screenshot, the yellow colored are copper traces, the one that touches cyan small box (excitation) is the path needs analysis, the rest are dummy. there is smd resistor and capacitor in between set as lumped RLC elements boundary. the orange color is the gnd with dense vias (surrounded by FR4) and solid ground plane underneath, directly connected to simple model of BNC connector with another excitation box on its output end. both excitations barely touch both signal path and gnd plane. gnd plane is set as reference node for excitations and also set as perfect E boundary. if i remove the perfect E boundary condition, i got different result. if i remove the "gnd plane as reference", i got another different result. there is very little explanation available whats going on with those parameter, i guess i will need a bit of know what and how an EM solver is. but all results are still too good to be true... in real life, there is alot of spectrum lost. the real life pcb only can be considered as 1GHz BW but the HFSS solver indicated they are acceptable beyond 10GHz  :-// :palm: behind this pcb section is nothing high speed, just low speed digital or i2c signals, regulator to the IC that generates signal to the analyzed signal path and many other smd components, i dont think they will matters, if they do, this will be a nightmare to both em modeller and pcb designer. and calculation to solve it will take much more time to complete.

T3sl4co1l:
OP's example; but that too.  Note that at frequencies this high (getting close in the 10s of GHz, on up to the 100s GHz that TheUnnamedNewbie has worked with), even via lengths and trace widths matter, so even (1-dimensional) transmission line methods become untenable and you are much better off with full field simulations.

Tim

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