22. Probe coupling.
a. Probe coupling operates, in effect, like a transmitting or receiving
antenna. When you use a probe to excite a cavity, it acts as a transmitting
antenna. When you use the probe to couple energy out of a cavity, the probe
acts as a receiving antenna. Figure 80 illustrates this comparison between
probes and antennas.
Figure 80.
Probe Coupling Compared to Antennas.
b. The receiving antenna in Part A of Figure 80 is picking up the
radiated electromagnetic waves of the transmitting antenna.
The probe in
Part B of Figure 80 is used to either pick up energy from the oscillating
cavity or excite the cavity.
You place the probe in the area of maximum
electric field to transfer maximum energy. If you move the probe away from
the maximum electric field, or shorten it, there is less transfer of energy.
c. You know there is maximum voltage in the area of maximum electric
current.
We say then, that probe coupling is characterized by the
following:
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