28. Klystrons have resonant cavities.
Klystrons are similar to magnetrons in that they also use resonant
cavities to produce microwave oscillations. Part B of Figure 83 shows the
cavity of a typical klystron tube. One wall of the cavity is a diaphragm.
You adjust the diaphragm to tune the cavity to the desired oscillator
frequency. Notice the loop in the klystron cavity. Like the magnetron, the
klystron uses loop coupling. You will learn more about klystron later on.
29. Final summary.
You have learned in this lesson sheet why we use resonant cavities
and some of their uses.
The most important points to remember about
resonant cavities are as follows:
(1) A
resonant
cavity
is
used
as
a
tuned
circuit
at
frequencies.
(2) A resonant cavity consists of a hollow chamber with conducting
walls.
(3) Resonant cavities have very low resistance and therefore have a
very high Q.
(4) Resonant cavities are made in various shapes, such as square,
rectangular, toroidal (doughnut shaped), and cylindrical.
(5) The energy in a resonant cavity is contained in its electric (E)
and magnetic (H) fields.
(6) The combination of E and H fields is called the electromagnetic
field.
(7) Four principle methods of tuning a resonant cavity are with a
plunger, a diaphragm, a screw, or a paddle.
(8) Three principle methods of coupling energy to or from a resonant
cavity are with a loop, a probe, or a slot.
(9) Resonant cavities determine the resonant frequency of echo boxes,
magnetrons, and klystrons.
120
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