24. Summary of coupling methods.
a. The three principle means of coupling energy into or out of a
resonant cavity are called loop coupling, probe coupling, and slot coupling.
b. The loop is placed in the area of maximum magnetic field.
c. The probe is placed in the area of maximum electric field.
d. When coupling energy out of the cavity, the slot is placed in the
area of maximum magnetic field, but when coupling energy into the cavity,
the slot is placed in the area of maximum electric field.
e. So far, you have learned how a resonant cavity works, and why they
are used at microwave frequencies.
Now, let's look at some practical
applications that you will run into as a repairman.
25. A resonant cavity is used in test equipment.
a. A resonant cavity is used as a piece of
radar test equipment called
an echo box. An echo box consists mainly of a
high Q resonant cavity that
oscillates when excited by a radar pulse. The
energy picked up is used to
check performance of the radar set. A typical
echo box setup is shown in
Figure 82.
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