Resonators
- Any distributed transmission line of length λg/2 will resonate if it is shorted or open at one end. This is the principle of resonators.
- A resonator is a device or system that exhibits resonance or resonant behaviour i.e., it naturally oscillates at some frequencies with greater amplitude than at other.
- These frequencies are known as resonant frequencies.
- The oscillations in a resonator can be either electromagnetic or mechanical.
- Resonators are used to either generate waves of specific frequencies or to select specific frequencies from a signal.
- Musical instruments use acoustic resonators that produce sound waves of specific tones.
Resonance
- It is a phenomenon that consists of a given system which is driven by another vibrating system or by external forces to oscillate with greater amplitude at some particular preferential frequencies.
- Resonance occurs when a system is able to store and easily transfer energy between two or more different storage modes.
Cavity resonator
- A device closely related to waveguides and of practical importance is the cavity resonators.
- If the waveguide is limited by closing the ends of a finite length of the tube in conducting surfaces then it is known as cavity resonator.
- The cavity resonators which are produced by placing end faces on finite length of cylindrical tube waveguides are known as cylindrical cavity resonators.
- Depending upon the cross section of the cavity resonator, there are two types of cylindrical cavity resonator rectangular and circular.
Cylindrical cavity resonator
In cylindrical cavity resonator we assume that
- The end faces are plane and perpendicular to the axis of cavity.
- The walls are perfectly conducting.
- The transverse cross sectional shape and size are uniform.
- The cavity is filled with loss-less non-conducting medium.
- In cylindrical cavity resonator E.M. wave propagates along the axis of the cavity and they reflects back and forth by the plane end faces.
- Both waves i.e., incident wave and reflected wave superpose and form a system of standing waves.
- It is found that the certain standing wave field distribution can be set up in the cavity corresponds to different cavity modes.
- The possible mode of frequencies are known as resonant frequency of the cavity.
- It is also found that the cavity resonator show the properties like an electronic resonant circuit i.e.,
- They can store energy in oscillating electric and magnetic fields.
- They can dissipate a fraction of the stored energy in each cycle of oscillation.
Advantage of cavity resonator over LC circuits
- The fraction of the stored energy dissipated per cycle is about 1/20 the fraction dissipated per cycle in L-C circuit.
- They have resonant frequencies which ranges from few megacycles, which is impossible in LC circuit.
To get the detailed knowledge about the resonator, cavity resonator and cylindrical cavity resonator click here.
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