transmission lines must be made smaller when you want to increase their
resonant frequency. When the resonant frequency required is so high that it
is impractical to use a transmission line section, we use a component called
a resonant cavity (Figure 71).
Figure 71. Resonant Cavities are Used at Microwave Frequencies.
2.
A resonant cavity is a type of resonant circuit.
A resonant cavity is a type of resonant circuit used at microwave
frequencies.
You will learn in this lesson why resonant cavities are
necessary in microwave radio and radar equipment.
You will also see how
resonant cavities are constructed and how they operate.
Next, you will
learn how to tune resonant cavities, and how to couple energy into them and
out of them.
Finally, you will see several practical applications of
resonant cavities as they are used in microwave oscillators and test
equipment.
3.
Before we talk about resonant cavities, let's review tuned circuits.
a. You know that a combination of inductance and capacitance is a tuned
or resonant circuit. To increase the resonant frequency of a tuned circuit,
you must use a lower value of inductance and capacitance. Resonant circuits
operating at very high frequencies (VHF) consist of only a few loops of wire
for the inductance and very small capacitor.
102
Previous Page
