Terminology » RF Components » Magnetron vs. Crossed Field Amplifier: Key Differences Explained

Magnetron vs. Crossed Field Amplifier: Key Differences Explained

magnetron amplifier radar oscillator rf system

Magnetron and Crossed Field Amplifier (CFA) are both crossed field microwave devices, meaning they operate using electric and magnetic fields that are perpendicular to each other. However, their functions differ i.e. magnetrons are oscillators, while CFAs are amplifiers. This article highlights the differences between a magnetron and a crossed field amplifier (CFA).

Magnetron

It is microwave oscillator which generates high power electromagnetic waves. It uses interaction between stream of electrons and magnetic field in a structure called resonant cavity. It consists of central cathode and surrounding anode with resonant cavities. Key features are as follows.

Available in frequency range from 1 to 40 GHz
Delivers output up to hundreds of kwatts.
Commonly used in ovens, radar transmitters, industrial heating.

Crossed Field Amplifier (CFA)

It is a microwave amplifier which uses crossed field principle similar to magnetron but it is designed to amplify input signal instead of generating one. It also has cylindrical structure with a cathode and anode. The key features are as follows.

Amplifies signal in GHz range
High power amplification often required in radar, satellites etc.
Nonlinear and low gain compared to TWTAs.

Key comparison between magnetron and crossed field amplifier

Feature	Magnetron	Crossed Field Amplifier (CFA)
Application	Used in communication equipment and radar transmitters as a pulsed or CW oscillator to generate high power output.	Used in intermediate or final stages of high-power radar systems.
Functionality	Oscillator with a single RF output connection.	Microwave power amplifier with both RF input and output connections.
Interaction Type	Continuous interaction between the RF field and the electron beam occurs over the entire length.	The RF field remains stationary.
Slow Wave Structure	Does not have a slow-wave structure.	Has a slow-wave structure similar to a Traveling Wave Tube (TWT). Forward wave CFAs use a helix, while backward wave CFAs use a bar line.

Summary

In conclusion, both the magnetron and crossed field amplifier utilize perpendicular electric and magnetic fields to operate at microwave frequencies. While the magnetron functions as a self oscillating high-power source, the CFA serves as a high-power amplifier for input microwave signals, each suited to specific applications like radar, communication and industrial heating.