user defined source option in xfdtd

xfdtd has an option for user defined source. when you click it, it opens a dialog box which browses for .src files. how do you make an src file. Should we code? How?. Also can this be used for defining arbitrary waveforms(like square or traingular)?

the online help says "setsourcesignal("name", t, amplitude, phase);" is the format. But how to write or how to use this info..

thanks and regards,

You might have the wrong documentation... Mine shows that the *.src file has a first line with the number of time steps in the file. After that, each line contains the source voltage and derivative of the waveform at a particular time step. The value of the derivative does not seem to matter. I just use the difference between two successive entries (see below).

It can be used to create an arbitrary waveform. You do have to round the transitions for a square or triangular waveform. Sudden transitions in FDTD introduce high-frequency signals not supported by the grid.

A quick example:
5
0 0
0.25 0.25
0.33 0.08
0.5 0.17
0.4 -0.1