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January 10, 2013 2:42pm UTC

Time stepping in time dependant solver for high frequencies

Hi

I have a problem simulating high frequency (in Mega Hertz) signals in time dependant domain. Even when I specify a high frequency time range in the study setting (exemple : range(0,5.0e-11,5.0e-7) ), it seems to me that Comsol is not considering those settings as time steps and it's calculating in a different time step (0.001s, I think). I was more convinced about this when I saw that running a simulation with a study setting close to that time step (such as range from 0 to 0.02s), it does give me the right result. So, I think that I must specify manually a more precise time step for the frequency signals to have a correct simulation.

So, I changed some time dependant solver configuration in time stepping such as BDF method with "strict" steps taken by solver, I tried with Generelized Alpha method with manual time step of 5e-11 and 0.5 amplification for high frenquency and so far, this doesn't seem to give appropriate results.

So here's my question: Since the study setting isn't actual calculation steps, but rather results. What should one do to specify a time step for calculation so that the study calculates using this step for more appropriate results for high frequency (small times). What's the paramters to configurate to do so ? Any help please ?

Thanks very much

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