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thliebig / openEMS

openEMS is a free and open-source electromagnetic field solver using the EC-FDTD method.
http://openEMS.de
GNU General Public License v3.0
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how to calculate time interval ? #84

Closed fwt1888 closed 2 years ago

fwt1888 commented 2 years ago

Hi, I came cross a problem. I want to know where time interval (i.e. dt) is defined or calculated in your code, because I think it is needed for calculation of f0 and fc.

thliebig commented 2 years ago

Well the calculation of dt is complicated (operator.cpp CalcTimestep). After the simulation it can be determined/read from several places. Maybe you can say what you want to do?? And would have the forum been a better place for this question?

fwt1888 commented 2 years ago

I want to set Gaussian excitation, but I'm not sure about the calculation of f0 and fc. I think timestep is needed in the forum related. Could you tell me the forum you use to calculate timestep? Thanks.

MrHighVoltage commented 2 years ago

AFAIK the maximum timestep is limited by the Grid settings (the minimum distance between two adjacent points). The timestep is, from my experience, much smaller then 1/(2*(fc+f0)), which is needed to keep within Nyquist–Shannon sampling theorem. Apart from that, I don't think you really need to know the time interval for the calculation of f0 and fc, because OpenEMS does that by itself. You only have to check if the time-step (as a result of your grid-resolution) somehow matches your required simulation frequencies.