Analysis of Dielectric Rods Supported Anistropically Conducting Rectangular Helix Slow Wave Structure
01 Mar 2019-pp 111-115
TL;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.
Citations
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01 Jan 2008
TL;DR: In this paper, Wu et al. describe a SWS called SWS, which is an extension of the HFSS, and describe the SWS as a "self-defense" system.
Abstract: 打印矩形的螺旋的一种新类型慢波浪的结构(SWS ) 在边界用匹配地的方法和电磁的不可分的方程被调查。包括分散方程和联合阻抗为的无线电频率特征横向反对称(奇怪) 这结构的模式被分析。数字结果同意很好，结果由 EM 模拟软件 HFSS 获得了。矩形的螺旋电路的分散被削弱，这被显示出，阶段速度在在矩形的螺旋 SWS 充满绝缘的材料以后被减少。作为平面慢波浪的结构，这结构在紧缩的 TWT 有潜在的应用程序。[从作者抽象]
7 citations
25 Apr 2023
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.
25 Apr 2023
TL;DR: In this article , a modified dispersion equation for the dielectric-loaded rectangular planar tape helix (PTH) is derived, simplified, and verified for mathematical symmetricity.
Abstract: The current limiting function, along with the other field boundary conditions, is used to obtain the approximate modified dispersion equation for the dielectric-loaded rectangular planar tape helix (PTH). The additional boundary condition employing the current limiting function confines the current density distribution within the surface region of the tape helix, thereby nullifying the fields in the gap regions of the PTH. Despite the increase in complexity of the electromagnetic boundary value problem, the accurate dispersion equation is derived, simplified, and verified for mathematical symmetricity. The derived dispersion equation is numerically computed for $\beta_{0a}(k_{0a})$ with a significant convergence rate for each root of the $\beta_{0a}$ function. The dispersion characteristics consisting of fundamental harmonic and few additional harmonics is plotted from a finite number of simultaneous equations approximated from an infinite set.
References
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TL;DR: In this article, an electron beam traveling with about 1/13 the speed of light is shot through a helical transmission line with about the same velocity of propagation, and the gain was achieved over a bandwidth 800 megacycles between 3-decibel points.
Abstract: Very-broad-band amplification can be achieved by use of a traveling-wave type of circuit rather than the resonant circuit commonly employed in amplifiers. An amplifier has been built in which an electron beam traveling with about 1/13 the speed of light is shot through a helical transmission line with about the same velocity of propagation. Amplification was obtained over a bandwidth 800 megacycles between 3-decibel points. The gain was 23 decibels at a center-band frequency of 3600 megacycles.
317 citations
Additional excerpts
...It mainly consists of vacuum tube, magnetic electron beam focusing system, electron gun, RF input, Slow Wave Structure (SWS) and a collector[1]....
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TL;DR: In this paper, the helix slow wave structure (SWS) of traveling wave tubes (TWT's) has been analyzed and a rigorous solution of the field equations, including the contribution of the space harmonics, was performed to evaluate the phase velocity and the interaction impedance up to millimeter-wave frequencies.
Abstract: In this paper, the helix slow wave structure (SWS) of traveling wave tubes (TWT's) has been analyzed. Dielectric supporting rods of arbitrary cross section have been considered in this analysis. The inhomogeneous dielectric loading factor has been accounted for by modeling the discrete support with a number of continuous dielectric tubes of appropriate effective dielectric permittivity. The helix tape model has been used for the field analysis. Furthermore the thickness of the helix tape has been considered. A rigorous solution of the field equations, including the contribution of the space harmonics, was performed to evaluate the phase velocity and the interaction impedance up to millimeter-wave frequencies. The nonuniformity of radial propagation constant over the structure cross section has been also included. With respect to other approaches, a closed-form expression of the field constants has been obtained. A study to choose the optimum number of space harmonics and dielectric tubes to be used in the analysis, has shown how the results are more sensitive to the number of space harmonics than to the number of dielectric tubes, beyond a certain number of the latter. The validity of this theory has been proved by comparison between measurements and simulations for helix SWS with different dimensions, rod shapes and operating frequency band.
80 citations
"Analysis of Dielectric Rods Support..." refers methods in this paper
...To obtain the dispersion relation of helical SWS there are two approaches and they are equivalent circuit and field analysis approaches[2,3]....
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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
Additional excerpts
...In this work, planar rectangular tape helix SWS is considered[4-6],[10]....
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TL;DR: In this paper, a planar slow-wave structure consisting of a straight-edge connection was studied in the context of application in traveling-wave tubes, and the effects of several practical modifications to the basic structure were examined.
Abstract: A planar slow-wave structure consisting of a planar helix with straight-edge connections has been studied in the context of application in traveling-wave tubes. The effects of several practical modifications to the basic structure are examined. These modifications comprise a vacuum tunnel, metal shield, and multilayer dielectric substrates. A modified effective dielectric constant method is proposed to obtain the dispersion characteristics for different possible configurations. Furthermore, coupling impedance for the different configurations has been calculated using the corresponding 2-D approximations. It is shown that, far from cutoff, the phase velocity and coupling impedance values calculated in this manner match very well with the simulation results obtained from CST Microwave Studio. The effects of variations in aspect ratio, metal shield distance, and dielectric constant of the substrates on phase velocity and coupling impedance are studied. A coplanar waveguide feed has been designed for one of the possible configurations. The measured S-parameters and phase velocity values for this proof-of-concept configuration agree well with the simulated results and confirm the ease of fabrication, low loss, and the wideband potential of the planar helix with straight-edge connections.
44 citations
"Analysis of Dielectric Rods Support..." refers background in this paper
...Hence, SWS are used to slow down the RF signal that travels at the speed of light so that electron beam can interact and amplify the RF signal....
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...The rectangular SWS is loaded with wedge shaped dielectric support rods enclosed within a conductor....
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...Keywords—planar TWT, SWS, tape helix, rectangular waveguide, boundary conditions, dielectric loaded, dispersion equation I. INTRODUCTION The basic characteristics of a Travelling Wave Tube (TWT) include high gain, low noise and wide bandwidth....
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...In this work, planar rectangular tape helix SWS is considered[4-6],[10]....
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...It mainly consists of vacuum tube, magnetic electron beam focusing system, electron gun, RF input, Slow Wave Structure (SWS) and a collector[1]....
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NEC1
TL;DR: In this article, a new design method was established for helix traveling-wave tubes having higher output powers (over 100 W) and wider bandwidths (2 to over 4 GHz) and capable of stable operation at frequencies in 10 to over 20 GHz bands.
Abstract: A new design method has been established for helix traveling-wave tubes having higher output powers (over 100 W) and wider bandwidths (2 to over 4 GHz) and capable of stable operation at frequencies in 10 to over 20 GHz bands. It is based on an analytical technique to consider the influences of the tape width, dielectric and shield barrel in the helix slow-wave circuit simultaneously, and also on an analytical technique to solve problems in regard to backward-wave oscillations at higher output powers, matching input and output sections for wider bandwidths, and undesired coaxial modes caused at operating frequencies above 20 GHz. This method realizes practical design of overall high-performance helix traveling-wave tubes with output powers of 250 W in the 14-GHz band and 20 W in the 30-GHz band and a bandwidth of 2 GHz in the 12-GHz band.
35 citations
"Analysis of Dielectric Rods Support..." refers methods in this paper
...To obtain the dispersion relation of helical SWS there are two approaches and they are equivalent circuit and field analysis approaches[2,3]....
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