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15 - Magnetrons

Published online by Cambridge University Press:  27 April 2018

Richard G. Carter
Richard G. Carter
Affiliation:
Lancaster University
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Summary

In a travelling-wave tube amplifier (TWT) a linear electron beam interacts with the longitudinal r.f. electric field of a slow-wave structure. Approximate synchronism between the electrons and the wave on the structure is maintained over a wide band of frequencies in low power tubes using helix slow-wave structures. High power tubes using coupled-cavity structures have narrower bandwidths. The structure is divided into two or more sections by severs to prevent feedback oscillations in high gain tubes. The initial velocity of the electrons is slightly greater than the phase velocity of the wave on the structure. The mean velocity of the electrons decreases as some of their kinetic energy is transferred to the wave and the beam becomes bunched. The power output saturates when the velocity of the bunches is equal to the velocity of the wave. The saturated output power can be increased by tapering the output end structure to reduce its phase velocity. Small- and large-signal modelling gives understanding of the principles of operation of a TWT including the factors affecting efficiency. The design of TWTs for octave bandwidth, multi-octave bandwidth, high efficiency, millimetre wave, and high power operation is considered in detail. Hybrid tubes are considered briefly.
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Information
Microwave and RF Vacuum Electronic Power Sources , pp. 565 - 628
Publisher: Cambridge University Press
Print publication year: 2018

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  • Magnetrons
  • Richard G. Carter, Lancaster University
  • Book: Microwave and RF Vacuum Electronic Power Sources
  • Online publication: 27 April 2018
  • Chapter DOI: https://doi.org/10.1017/9780511979231.015
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To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.

  • Magnetrons
  • Richard G. Carter, Lancaster University
  • Book: Microwave and RF Vacuum Electronic Power Sources
  • Online publication: 27 April 2018
  • Chapter DOI: https://doi.org/10.1017/9780511979231.015
Available formats
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Save book to Google Drive

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.

  • Magnetrons
  • Richard G. Carter, Lancaster University
  • Book: Microwave and RF Vacuum Electronic Power Sources
  • Online publication: 27 April 2018
  • Chapter DOI: https://doi.org/10.1017/9780511979231.015
Available formats
×