Large Signal Field Analysis of Linear Beam Travelling Wave Tube Amplifier for Anisotropically Conducting Tape Helix Slow Wave Structure Supported by Dielectric Rods | Shiv Nadar University
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Large Signal Field Analysis of Linear Beam Travelling Wave Tube Amplifier for Anisotropically Conducting Tape Helix Slow Wave Structure Supported by Dielectric Rods

Travelling wave tube amplifier(TWTA) is a microwave vacuum electronic device predominantly used in satellites and defence RADARs for its stable operation at high power levels and much wider bandwidths. The TWTA consists of an electron gun to generate a linear electron beam, an interaction region in which RF input signal to be amplified interacts with the electron beam, and a collector at which the spent electrons are collected. The interaction region consists of dielectric rods supported slow wave structure(SWS) which slows down the RF signal for the beam-wave interaction(BWI). The SWS considered here is a practically relevant anisotropically conducting tape helix wound along axial coordinate, in which the tape surface current density is in parallel to the tape winding ignoring its variation along the perpendicular direction. The electron beam in the interaction region is modelled using the Lagrangian approach in which, the electron arrival time within the beam is represented as a function of the electron entrance time, its axial and radial coordinate. In the large signal modelling of the interaction region, the novel approach incorporating this Lagrangian model of the electron beam together with the much accurate tape helix model is of high importance as the existing modelling techniques consider multiple approximations in their formulation. Using Green's function sequence, the field components in the SWS are designated as nonlinear functionals of electron arrival time.  The electron arrival time in the beam region is formulated into a nonlinear operator in the Banach space mapping form by substituting the axial electric field component into the electron ballistic equation. The nonlinear beam-wave interaction is then obtained by determining the electron arrival time through extensive successive approximations, and thus exact electric and magnetic field components in the tape helix SWS are attained. The numerical computation of the proposed model yields definitive analytical results for the electron exit velocity, induced surface current density, power gain, conversion efficiency and optimum interaction length.

Department: 
Electrical Engineering
Year: 
2018
Student Name: 
Richards Joe S
Faculty Advisor: 

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