Time monitor nearest mesh cell interpolation meaning

fdtd

#1

Hi, I would like to know what kind of spatial interpolation (linear, spline…) is done in the “nearest mesh cell” option defined in the advanced tab of the time monitor [https://kb.lumerical.com/en/ref_sim_obj_monitors_time.html]

Does it also take into account any kind of time interpolation to define the magnetic and electric fields at the same time? (Recall the leapfrog structure of the FDTD algorithm).

Thanks in advance,
Marcos


#2

I think the fields are interpolated linearly when you choose to turn on the interpolation (it is on by default). In this case, the fields are returned at the nearest grid point. Imagine that the time monitor is snapped to the nearest grid point. If you are familiar with a Yee cell (ie the field components are calculated at a different position in a Yee cell), the fields are interpolated such that the fields are returned at the same location. The “advanced tab” in the time monitor page you are quoting more information about this setting.

It is true that the fields (E and H) are calculated at different time point - off by half a time step. In FDTD Solutions, the fields returned will be sharing the same time vector after some interpolation in the time domain is done.