Working of Two Cavity Klystron Amplifier and Application

Two Cavity Klystron Amplifier 

Diagram of  Two Cavity Klystron Amplifier 

• Fig show above two cavity klystron amplifier.
• It is a widely used microwave amplifier operated by principles of velocity and current modulation.
• Assume that the input signal is smaller than the dc accelerating voltage.
• All electrons injected from the cathode arrive at the first cavity with uniform velocity.
• Those electrons passing the first cavity gap at zero gap voltage pass through without change in velocity.
• Those passing through the positive half cycle of gap voltage pass with an increase in velocity.
• Those passing through the negative half cycle of gap voltage pass with a decrease in velocity.
• The above action results from the variations in electron velocity gradually bunching together when those travel down the drift space.
• And the variations in electron velocity in the drift space are known as velocity modulation.
• The density of the electrons in the second cavity gap varies cyclically with time.
• The electron beam contains an ac component and is said to be current-modulated.
• Maximum bunch occurs midway between the second cavity grids during its retarding phase.
• Therefore the kinetic energy of electrons is transferred to the field of the second cavity.
• The electrons emerge from the second cavity with reduced velocity and terminate at the collector.
• As shown in Fig. above cavity close to the cathode is the bunches cavity or input cavity, which modulates the velocity of the electron beam.
• the second cavity is the catcher cavity or output cavity, it catches energy from the bunched electron beam.  
• Some characteristics of two-cavity klystron amplifiers are as follows:
• Efficiency=about 40%
• Power gain =about 30dB
• power output= average power is upto 500kw

Application : 
Application of 2 cavity klystron amplifier are as follows:

• As power output tube in UHF TV transmitter in satellite communication ground station in radar transmitter.
• As a power oscillator (5-50GHz).

👉Multicavity Klystron Amplifiers 

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