let's consider this picture in which a cylindrical resonant cavity is excited through a waveguide.
I have some questions:
1) Why is it called "Magnetic Coupling"? I thought this excitation simply was the propagation (through the slot) of the wave already present in the waveguide towards the resonant cavity
2) Why is there a magnetic loop in the last two pictures? what are its terminals connected to? Should be present also in the first two pictures?