Microwave Engineering Reflex Klystron - Microwave Engineering

What is Microwave Engineering Reflex Klystron?

Klystron is a microwave generator that works on reflections and oscillations in a single cavity, which has a variable frequency.

Reflex Klystron contains of an electron gun, a cathode filament, an anode cavity, and an electrode at the cathode potential. It offers low power and has low competence.

Construction of Reflex Klystron

The electron gun produces the electron beam, which permits through the gap in the anode cavity. These electrons traverse towards the Repeller electrode, which is at high negative potential. The electrons repel back to the anode cavity, Due to the high negative field. In their coming back journey, the electrons give more energy to the gap and these oscillations are sustained. The constructional details of this reflex klystron is as shown in the resulting figure.


It is expected that fluctuations previously exist in the tube and they are continued by its operation. The electrons while transient through the anode cavity, gain some velocity.

Operation of Reflex Klystron

The operation of Reflex Klystron is agreed by some norms. The electron beam is enhanced towards the anode cavity.

Let us take up that a reference electron er crosses the anode cavity but has no extra speed and it resists back after reaching the Repeller electrode, with the same velocity. Another electron, let's say ee which has started previous than this reference electron, extents the Repeller first, but returns gradually, reaching at the same time as the reference electron.

We have extra electron, the late electron el, which starts later than both erand ee, though, it moves with better speed while returning back, reaching at the same time as er and ee.

Currently, these three electrons, namely er, ee and el reach the gap at the similar time, forming an electron bunch. This travel time is called as transit time, which should have an best value. The resulting figure illustrates this.

The anode cavity hurries the electrons while going and gains their energy by retarding them during the return journey. When the gap voltage is at maximum positive, this lets the maximum negative electrons to retard.

The optimum transit time is represented as

This transit time depends upon the Repeller and anode voltages.

Applications of Reflex Klystron

Reflex Klystron is used in applications where variable frequency is desirable, such as −

  • Radio receivers
  • Portable microwave links
  • Parametric amplifiers
  • Local oscillators of microwave receivers
  • As a signal source where variable frequency is desirable in microwave generators.

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