Hi! Stepped frequency continuous wave, as you describe it, seems inpractical for me. Any coarse frequency change will cause high harmonics wave, which may lead to numerous artifacts. Even using very small frequency steps you should still make sure that any such change will not cause abrupt change of fields. For example, you may sync any frequency change to zero crossing, but even in such case there will be unwanted distortions. I mean, that cos( 2*pi* (fo + i*delta_f) *t) - cos( 2*pi* (fo + (i+1)*delta_f) *t) may be anything from -1 to +1 (in other words, phase difference between them is oscillating), and not close to 0, as one would expect.
Chirped source, as described in http://en.wikipedia.org/wiki/Chirp may be better suited for your task and doesn't have such problem. In my previous experience I found that exponentially chirped source is better that the linear because the number of oscillations at any given frequency is more or less comparable, unlike linearly chirped source. I had implemented it in python, but, of course, custom sources are also easily implementable with scheme or c++ . Hope it helps, Shawkat Nizamov 2010/5/4, Shravan S <[email protected]>: > Hi, > I am interested in simulating an SFCW (Stepped frequency continuous wave) > source in meep. So, for every interval of time, the frequency of the > transmitted signal changes by a small value delta_f. The number of intervals > go up to 400 or even 4000, so specifying a start time and end time for each > frequency step seems impractical. I wanted to know if I could loop it in > some way. The equation for SFCW is given as, > Ao cos( 2*pi* (fo + i*delta_f) *t ).. where i=1,2,3.... N; N=no. of > frequency steps > > Thank you, > Shravan > _______________________________________________ meep-discuss mailing list [email protected] http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss
