If I use PML to y in this case then the simulation does not converge, I mean with time the auto-shout off values keep increasing and no value recorded from the sweep. My structure is periodic both x and y with different period size, but I was trying to calculate only one direction Ky. You should not change the FDTD size or spans other than ONE period in periodic axis. but same set up if I lower the FDTD size to much smaller size compared to the period size then I can see those bands. "I noticed a lot of simulation when I increase the FDTD region size to the period size of the periodic structure then all the bands fall in a line (in same frequency for all ky values). In your case, Y axis is periodic, but x axis is not. "Also for 1D say only for ky dispersion curve can I put block BC for both y and x direction, provided the dipole source is z direction."īloch BC is a periodic BC and can only be used in periodic axis.
"what is the condition for 1D and 2D bandstructure calculation and FDTD size? "Īs mentioned before, in the periodic axis, the FDTD size or span must be a period, whether it is 1D or 2D My suggestion is to position the periodic BCs at relatively uniform area. so you can set the location of the periodic boundary any where as long as the simulation span is one period. However, since the structure is periodic, it has no beginning or ending point. The simulation span determines what is the period. "For bandstructure and dispersion calculation, should FDTD region has to be the same side of a period size?"Īs a rule of thumb, FDTD region should match the periodic boundary when it is periodic, eg, infinitely periodic.