TWT vs Klystron-Difference between TWT and Klystron

This page on TWT vs Klystron describes difference between TWT and Klystron. Let us understand TWT and Klystron basics before we look into comparison between the two.

TWT-Travelling Wave Tube


It is one of the important microwave tubes mainly used for wide bandwidth, high gain, low noise and moderate peak and average power requirement. The TWTs are of two types viz. helix TWT and coupled cavity TWT. The function of modules such as electron gun, magnet, collector is same as used in klystron described below. The major difference between klystron and TWT is that klystron cavities are replaced by structure of helix shape in TWT. The figure-1 depicts TWT.
READ MORE Microwave Tubes➤➤ and READ MORE TWTA vs SSPA➤➤


Klystron is one of the high power vacuum tubes used in radar system as amplifier and oscillator. It is similar to pipe organ tube where in air in the tube vibrates and produces sound energy of desired frequency. In klystron, instead of air, electrons are used which vibrate at desired frequency inside the glass tube and generates microwave energy.

Two cavity Klystron

Klystron usually will have two or more cavities as per gain and bandwidth requirements needed for different applications. Klystrons are of two types as mentioned below:

• Two cavity Klystron or Multi-cavity Klystron: They are used as low power amplifier. There are two cavities in two cavity klystron i.e. buncher cavity and catcher cavity. There are intermediate cavities between buncher and catcher cavities in multi cavity klystron. More number of cavities are used to achieve very high gain and bandwidth. The figure-2 depicts two cavity klystron.

• Reflex Klystron: Used as Oscillator. It is a single cavity device. It is known by this name due to its reflex action of electron beam. The difference between reflex and two/multi cavity klystron is that, reflex klystron uses single cavity for modulation/demodulation. Moreover it uses repeller inplace of catcher cavity.

Klystron works on the principle of velocity modulation of electrons. In klystron strong electrostatic fields are required for its operation efficiently.

TWT Klystron
Interaction between EM field and beam of electrons in TWT is continuous over the entire length. Interaction in klystron occurs only at the gaps of resonant cavities.
In coupled cavity TWT, coupling effect takes place between cavities. In klystron each cavity operates independently and there is no mutual coupling.
TWT does not have resonant cavity. It uses helix structure. Klystron has resonant cavities.
TWT has wider bandwidth of operation. Klystron has smaller bandwidth of operation.
TWT operates on lower efficiency. Klystron has comparatively high efficiency.
There are two types viz. helix and coupled cavity. There are two types viz. Two or Multi-cavity , reflex klystrons
Frequency of operation is from 300 MHz to 50 GHz Frequency of operation is from 4 to 200 GHz
Handles CW power upto 200Watt Handles power of 1 mW to 2.5 W

TWT and Klystron related links

SSPA Test Procedure   Power Amplifier Basics and SSPA design example   TWT calculator   microwave tubes    Reflex Klystron Calculator   TWTA vs SSPA-Difference between TWTA and SSPA  

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