Computer Aided Design of A Helix Travelling-Wave Tube

The basic design of a TWT is obtained in stages for the given design parameters in respect of bandwidth (BW), gain, output power, efficiency, signal to noise ratio, and AM-to-PM conversion coefficient using analytical methods or available database. The final design is achieved by optimization, using computer-aided design (CAD) packages for individual sections.Generally, one may choose to first proceed with the design of slow-wave structure (SWS). The type and geometry of SWS is decided by the dispersion, which decides the BW, and interaction impedance, which decides the gain. Initial estimates of helix radius and pitch are first made on the basis of helix voltage and dielectric loading factor. At the initial stage, small signal model is used to check the parameters of the SWS, which are then optimized using the large signal model of beam-wave interaction.In the second stage, the basic design of electron gun is carried out using simple Pierce synthesis techniques. This is then optimised using electron gun ...

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