Excitation of Cavity Resonator
There are following methods of cavity resonator excitation.
Loop Excitation
As shown in the given diagram, the loop excitation is carried out in the cavity resonator by introducing the loop inside the cavity. The loop is inserted from the narrow dimension of the cavity and it should be kept at the place inside the cavity where magnetic field is maximum.
When the R.F signal is applied through the loop. The magnetic flux starts to expand and collapse around the loop. This magnetic flux causes to induce the voltage in the walls of cavity resonator. As the induced emf is the microwave signal, therefore, the oscillation action inside the cavity resonator takes place.
Probe Excitation
As shown in the given diagram. The probe excitation is carried out in the cavity resonator by introducing the probe inside the cavity. The probe is inserted from the broad dimension of the cavity and it should be kept at the place inside the cavity where electric field is maximum.
When the R.F signal is applied through the probe, the electric field starts to expand and collapse around the probe, this electric field causes to excite the cavity resonator and the oscillation inside the resonator takes place.
Aperture Excitation
As shown in the given diagram, the aperture excitation is carried out by making the slot in the cavity resonator. In this case we couple the E-Field or H-Field to the cavity with the help of a circular or rectangular waveguide. This field causes to excite the cavity resonator. If the coupling is carried out from the broad dimension of the cavity resonator, the operation will be TE mode. If we couple the input from the narrow dimension the operation will be in TM mode.