I'm interested in getting feedback from members of this group on how you use PCB field solvers and what type of features are important to you and what features are missing in available solutions. Feel free to discuss the finer points between low and high frequency traces and loss.
I'm often asked by clients on what type of field solver should be used for the task at hand and of course I have my own opinions but thought it would be interesting to hear from others.
Here are some thoughts for discussion points:
- Impedance calculation. This is an easy one because you need to be able to determine the impedance of a PCB trace based upon the geometry. However I find that a lot of people throw full 3D solvers at stackups where even an equation based solver works fine. How important is accuracy when doing pre layout analysis? Would you sacrifice 2% accuracy for a faster solution?
- Cross Talk. Some field solvers will give you the backwards crosstalk coefficient which is useful but there's not a lot of available non-simulation crosstalk analysis features without running coupled net simulations. Some easy metrics to calculate are voltage amplitude induced on victims (forward and backward or near and far) and the change in impedance and delay due to coupling. What sort of metrics do you use for PCB crosstalk sign off? What do you think is missing?
- Loss. A lot of tools will plot the trace loss vs frequency for you but how useful do you feel that data plot is on its own? Obviously having a simulation model with proper loss is a benefit. Is a metric like loss per inch in dB useful when sizing up the topology and layout for an interface? Let's take a PCI Express interface that has a defined interconnect loss - is it useful to try and match up the PCB layout loss budget? How accurate do you think a tool can get without running full simulations with pattern dependencies?
Looking forward to your responses