
154 Microwave Engineering
4.6 Coupling Mechanism
Cavity resonator is a metallic enclosure whose physical dimensions are
directly related to the operating frequency. Since it is a complete enclosure,
it requires a small opening for feeding energy into it or for taking it out. The
mechanism of feeding or taking out is referred to as coupling. This coupling
mechanism has to be so located so as to excite a desired mode into the cav-
ity. Also, the larger the opening, the tighter the coupling and the greater the
effect on the resonant frequency. As in waveguides, the methods of coupling
the energy to a cavity include (a) probe coupling, (b) loop ...