I would like to simulate a capacitor with alternating current at a frequency of 50 Mhz. Simulation in EM LF Eletro Static like in the tutorial "two parallel plates" works fine. But how can I build a model that works in EM FDTD simulation?
For FDTD simulation, you will need to excite the plates by joining them with a wire (use the Sketch -> Lines tool), as if you were building a circuit. Leave a small interval open somewhere so that you can insert an edge source.