The analysis of 3 dB microstrip directional coupler in time-varying media by FDTD method

The characteristics of time-varying media are very important for electromagnetic research; many microwave components should be studied in time-varying media, and some of these will not work well because of the influence of the time-varying medium. In this paper, FDTD difference equations in time-varying media are deduced in the three-dimension case, and then using it to simulate the electromagnetic pulse's propagation in a 3 dB microstrip directional coupler to show whether the transmission characteristic will be changed when the media parameters vary by some rules. By comparing its operating characteristics with that in homogenous static media, we can see that it does not work well.