Effect of the finite thickness of the helix wire on the characteristics of the helical slow-wave structure of a traveling-wave tube

Space-Harmonic Effects in Helical Slow-Wave Structure --- an Equivalent Circuit Analysis

“…The analytical results presented here also pass on to those, reported elsewhere, as a special case, by considering same radial propagation constant and for the fundamental mode only [7][8][9]. Moreover, in the analytical results the effect of helix wire/tape thickness [13,14] has been ignored but considered in the actual analysis. Finally, the results for the axial propagation constant of the fundamental mode has also been validated with those experimental values published in the literature [15].…”

“…The present simple and elegant analysis of a helical structure includes the space harmonics considering axial periodicity of the sheath helix [12], the finite helix thickness [13,14], the structure inhomogeneity for the dielectric supports deviating from the simple wedge geometry [4] from and the non-uniformity of radial propagation constant over the structure cross section. This makes the present analysis more general and capable of dealing with a wide range of structure parameters.…”

“…In the analytical model, considered here, has n + 2 regions ( Fig. 1b): the free-space region (p = 1, ε r,1 = 1, 0 ≤ r ≤ a) inside the winding radius (r = a) of the helical sheath, the free-space gap (p = 2, ε r,2 = 1, a ≤ r ≤ b 0 ) between the sheath and the beginning (r = b 0 ) of the dielectric regions, to take into account the finite helix wire/tape thickness [13,14]…”

Analytical Exploration of New Tapered-Geometry Dielectric- Supported Helix Slow-Wave Structures for Broadband TWT's

“…However, when the supports deviate from the simple wedge geometry, one could use a model in which the discrete supports are azimuthally smoothed out into a number (n) of homogeneous continuous dielectric tube regions of appropriate permittivity values instead of a single dielectric tube [11,12]. The problem is then essentially a boundary-value problem involving boundaries between (n + 2) continuous regions: 1) the free-space region inside the helical sheath, 2) the free-space region of the gap between the sheath and the beginning of the dielectric which is usually considered to take into account the effect of the finite helix wire/tape thickness [13,14], 3) n continuous, homogeneous dielectric tube regions simulating the discrete supports. In this model one may increase the number of such discrete tubes until convergence in results is obtained.…”

GA‐based optimisation of the interaction structure of an X‐band helix travelling wave tube

“…The SWS of a typical helix TWT could be of a single section or multiple sections with each section consisting of multiple subsections and will necessarily have multiple pitches of different lengths, suitably supported by dielectric support rods and surrounded by an envelope [4,5]. Furthermore, each section of helix comprises of several other parameters, namely tip loss, centre loss and distributed loss and the sections may also be separated from each other by several sections [6,7].…”