# Modified Accurate Dispersion Characteristics with field restricted current density distribution for Open Rectangular Planar Tape Helix

25 Apr 2023-pp 1-2

Abstract: A rectangular open tape helix is analysed for its dispersion characteristics by deriving the dispersion equations that restrict the fields within the tape helix region by incorporating a confinement function. The dispersion equations are derived by applying the accurate boundary conditions to one-quarter of the structure in axial and transverse directions owing to the symmetricity of the rectangular helical waveguide. The dispersion characteristics are numerically computed from an infinite number of simultaneous equations. The computed characteristics is compared with the theoretical model of sheath helix consisting of only the fundamental harmonics. Plotted dispersion characteristics reveals the potential usability of such devices as compact traveling wave tubes by miniaturization and can be printed.

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TL;DR: In this article, a special type of helical slow-wave structure encompassing a rectangular geometry is investigated, and the slowwave characteristics are studied taking into account the anisotropic conducting helix.

Abstract: A special type of helical slow-wave structure encompassing a rectangular geometry is investigated in this paper, and the slow-wave characteristics are studied taking into account the anisotropically conducting helix. By using the electromagnetic integral equations at the boundaries, the dispersion equation and the interaction impedance of transverse antisymmetric modes in this structure are derived. Moreover, the obtained complex dispersion equation is numerically calculated. The calculation results by our theory agree well with the results obtained by the 3-D EM simulation software HFSS. The numerical results reveal that the phase velocity decreases and interaction impedance increases at higher frequencies by flattening (increasing the aspect ratio of) the rectangular helix structure. In addition, a comparison of slow-wave characteristics of this structure with a conventional round helix is made.

47 citations

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TL;DR: In this article, a rectangular tape helix slow-wave structure with infinitesimal thickness and finite width in free space is investigated, and the dispersion properties and the interaction impedance for transverse antisymmetric modes are obtained.

Abstract: A rectangular tape helix slow-wave structure with infinitesimal thickness and finite width in free space is investigated. With the expansion of surface currents in the helix and the applications of the modified Marcatili’s method, as well as average power flow matching method at the boundaries, the dispersion properties and the interaction impedance for transverse antisymmetric modes in a rectangular tape helix immersed in free space are obtained. It is shown that, compared with the results of the simplified sheath model by previous researchers, higher accuracy has been obtained between the calculation results of the present theory and the data obtained from HFSS, and the validity of the present theory is further demonstrated by comparison with experiments. The improved characteristic equations hold scientific and practical significance in the design and performance evaluation of such plane slow-wave structure in the application of compact traveling-wave tubes. The distribution characteristics on the cross section of the longitudinal electric field fundamental component are also discussed based on this theory.

18 citations

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TL;DR: In this article, the approximate distribution of the current density induced on the tape surface by guided electromagnetic waves supported by an inflnite open tape helix is estimated from an exact solution of a homogenous boundary value problem for Maxwell's equations.

Abstract: The approximate distribution of the current density induced on the tape surface by guided electromagnetic waves supported by an inflnite open tape helix is estimated from an exact solution of a homogenous boundary value problem for Maxwell's equations. It is shown that the magnitude of the surface current density component perpendicular to the winding direction is at least three orders of magnitude smaller than that of the surface current density component parallel to the winding direction everywhere on the tape surface. Also, the magnitude and phase distribution for the surface current density components parallel and perpendicular to the winding direction are seen to be nearly uniform at all frequencies corresponding to real values of the propagation constant.

9 citations

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20 Oct 2011TL;DR: In this paper, the edge conditions for a perfect electrically conducting wedge in a medium with negative permittivity were investigated, and an optimization technique was used to solve the problem numerically.

Abstract: The work disclosed herein investigates the edge conditions for a perfect electrically conducting wedge in a medium with negative permittivity. A typical structure has been assumed in accordance with previous works for ordinary media, and an optimization technique has been used to solve the problem numerically. Special cases of importance have been explored mathematically.

5 citations

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01 Mar 2019TL;DR: In this paper, the dispersion equation of a dielectric loaded anisotropic conducting tape helix slow wave structure for planar TWTs is derived through accurate boundary conditions that restrict the field only on the tape surface and not in the gap regions.

Abstract: The dispersion equation of a dielectric loaded anisotropically conducting tape helix slow wave structure for planar TWTs is derived. By assuming the current density behavior on the rectangular tape helix, the dispersion relation is obtained through accurate boundary conditions that restrict the field only on the tape surface and not in the gap regions. Substitution of the field equations in the boundary conditions results in the six complex constants of the field equations. The complex constants are re-substituted in the last boundary condition that consists of the restricting function or the indicator function to arrive at the dispersion equation. The derived dispersion equation can be used to obtain the dispersion characteristics for a more practically relevant planar TWT interaction structure.

3 citations