Enhancement of Non-linear Effects in Traveling Wave Tubes (TWTs) for Space Applications

EasyChair Preprint 7640

Abstract

Traveling wave tubes (TWTs) are high-power microwave amplifiers based on vacuum electronic technology. They are widely used as high-power RF amplifiers in the transponders of communication satellites. More than 60 TWTs of different frequency bands, e.g., C-band (3.6-4.3GHz), Ku-band (10.9-11.75GHz), and Ka-band (20.6-21.3GHz) are used in a normal-size communication satellite. Due to overcrowding of C-Band frequencies the satellite communication systems migrated to Ku-band and Ka-band frequencies. The design and development of space TWT require special considerations in order to achieve broad bandwidth, high flexibility, high efficiency, high linearity, and long life. High linearitywith phase shift less than 30 degrees and high efficiency of more than 60% of a space TWT are highly desirable requirements for communication. Non-linearity of a space TWT is specified by the noise-power ratio (NPR), carrier-to-intermodulation level (C/3IM), 1 dB compression point, and multi-signal intercept points. The Large Signal Model (LSM-1D and 2.5D) is a specialized program for the analysis of non-linear beam-wave interaction in TWTs. SUNRAY is a simplified and improved large-signal code for helix TWTs that takes into account both the loss and circuit variation along a tube and the inherent backward wave and reflection due to mismatch at the input and output coupler. CST-PS is another code for 3D electromagnetic analysis and design of TWTs in the high-frequency range. The results for the gain and the output power over the operating band given by these two codes were found to be comparable but the SUNRAY code is faster in comparison to the CST code. It takes less than a minute to simulate the RF performance of a typical high-frequency TWT at a single frequency. In this paper, the design and development of a space TWT for improved linearity and high efficiency will be presented with a detailed description of the proposed tools for modeling and analysis of TWTs.

Keyphrases: RF Amplifiers, Traveling wave tubes, communication, efficiency, high linearity

@booklet{EasyChair:7640,
  author    = {Ashok Kumar and Renu Malsaria and Amitavo Roy Choudhury and Nitika Choudhary},
  title     = {Enhancement of Non-linear Effects in Traveling Wave Tubes (TWTs) for Space Applications},
  howpublished = {EasyChair Preprint 7640},
  year      = {EasyChair, 2022}}