The practically important case of dielectric loaded tape helix enclosed in a perfectly conducting coaxial conductor is analysed in this paper. The dispersion equation for the infinitesimally thin and anisotropically conducting tape is derived from an exact solution of a homogeneous boundary value problem for Maxwell's equation. The boundary value problem is solved to yield the dispersion equation which takes the form of the solvability condition viz., the determinant of the infinite-order coefficient matrix is zero. For the numerical computation of the approximate dispersion characteristics, all the entries of the symmetrically truncated version of the coefficient matrix are estimated by summing an adequate number of the rapidly converging series for them. The numerical computation of dispersion characteristics and phase speed variations for different values of b/a (outer conductor to inner helix radius) and effective dielectric permittivity is presented. © 2014 IEEE.

Naveen G Babu

Electrical Engineering

(SoE) School of Engineering

Stanislaus R.J.

Joshi S.

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Shiv Nadar University

Wave propagation characteristics in anisotropically conducting dielectric loaded tape helix slow wave structures

IEEE International Vacuum Electronics Conference, IVEC 2014

The large-signal behavior of traveling wave tube amplifier for a linear beam dielectric loaded anisotropically conducting tape helix slow wave structure (SWS) is realized through a swift and reliable field analysis. 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. © 2017 Informa UK Limited, trading as Taylor & Francis Group.

Journal of Electromagnetic Waves and Applications

Large-signal field analysis of a linear beam travelling wave tube amplifier for the anisotropically conducting tape helix slow-wave structure supported by dielectric rods

The tape helix slow wave structures used in travelling wave tube (TWT) amplifiers are exploited for use as radiating devices through the fast wave analysis. The dispersion equation is derived from accurate boundary conditions that neither involve assumptions on the current density distribution, nor considers a defined distribution function for a dielectric loaded tape helix slow wave structure surrounded by a conductor or a conductor placed inside the tape helix. Analytical computation of the dispersion characteristics of both the structures revealed the presence of fast wave modes usable for applications such as antennas. © 2016 IEEE.

Proceedings - 2016 International Conference on Micro-Electronics and Telecommunication Engineering, ICMETE 2016

Fast wave propagation characteristics of dielectric loaded tape helix structures placed around and within a cylindrical core

The practically important case of a dielectric-loaded tape helix enclosed in a coaxial perfectly conducting cylindrical shell is analysed in this paper. The dielectric-loaded tape helix for guided electromagnetic wave propagation considered here has infinitesimal tape thickness and infinite tape-material conductivity. The homogeneous boundary value problem is solved taking into account the exact boundary conditions similar to the case of anisotropically conducting open tape helix model [1, 2]. The boundary value problem is solved to yield the dispersion equation which takes the form of the solvability condition for an infinite system of linear homogeneous algebraic equations viz., the determinant of the infinite- order coeficient matrix is zero. For the numerical computation of the approximate dispersion characteristic, all the entries of the symmetrically truncated version of the coeficient matrix are estimated by summing an adequate number of the rapidly converging series for them. The tape-current distribution is estimated from the null-space vector of the truncated coeficient matrix corresponding to a specified root of the dispersion equation.