what is cavity resonator and its basic function
This page cavity resonator basics and also mention cavity resonator function. It mentions link to rectangular and circular cavity resonator calculators.
A waveguide is basic microwave device used for various applications. The portions of waveguide are used as directional coupler, hybrids, duplexers, circulators and even as cavity resonator.
The Cavity resonator is short segment of waveguide which acts as high Q resonant circuit. As shown in the figure-1, a simple cavity resonator is formed using a shirt piece of waveguide 1/2 wavelength in size. A small probe is fixed at the center which injects the microwave energy. This small waveguide portion is shorted on both the ends using metallic piece.
Due to shorts at both the ends, signal injected from the probe will gets bounced from the short positions on both the sides. Even if signal is not injected at the probe, wave will keep bouncing till it die due to waveguide losses. This effect is known as resonance and circuit formed as parallel resonant circuit.
The cavity as mentioned has very high Q factor upto about 30000. Due this fact, cavities are used to design microwave filters and other resonant circuits.
Tunable Cavity Resonator
There are various types of cavity resonator viz. circular and rectangular. Other than the fixed cavity resonator as mentioned in the figure-1, there also exists tunable cavity resonator. In this type of cavity resonator, one wall of cavity is made movable.
Figure-2 depicts cylindrical cavity with adjustable disks. An adjustment screw moves the end wall which will adjust the resonant frequency. The smaller the cavity size, higher is the operating frequency.
Tunable cavity resonators are also available with tunable plugs.