This paper discusses the causes of and some solutions to the commonly obser
ved problem of de field offsets in finite-difference time-domain (FDTD) sim
ulations. DC electric and magnetic field offsets are shown to be valid calc
ulated responses of the modeled systems, resulting from interaction between
the turn-on characteristics of the source and the properties of the models
. The de offsets may be avoided in the time domain by tailoring the source
waveforms or in the frequency domain by post-processing the FDTD output.