Hi,
Even if the excitation is a plane wave, you may still obtain the reflection. There is a discussion on the board about that. So, it may be possible to obtain the Q-factors.
Added after 5 hours 47 minutes:
Hi,
I checked your structure. A couple of remarks about the structure:
This is a highly resonant structure. So to get the resonant frequency correctly, you need to care for two things. First, you need to let the energy to drop to -80 dB. Second, you need to determine the high field locations in your structure. Because, these locations contribute to the response of the structure the most. For the case of split ring, it is important to accurately describe the split. For a fine simulation, to my experience, you need at least 4 mesh cells inside the split. One more final remark, Instead of using the H-probe, I would suggest locating an E-probe some distant away from the structure to determine the transmission. The resonant frequency will appear as a dip in the transmission. And it will be quite sharper.