Slow-Wave Structures For Traveling-Wave Tubes Research Articles

Estimation of RF-wall loss in slow-wave structures for traveling-wave tubes

Return-loss resonance method is used to estimate the loss per unit length of two different slow-wave structures namely a tapered ferruled coupled-cavity structure operating at centimeter-wave band and a ferrule-less folded-waveguide structure operating at millimeter-wave band. The loss estimated by this method was found to be within 2.5% and 5% compared against those obtained using conventional transmission loss method (S21 value) and numerical simulation carried out using CST-Studio. This approach was found to be very simple yet reasonable accurate to estimate the loss of the periodic structures operating in cm- and mm-wave bands.

Accurate and Fast Finite-Element Modeling of Attenuation in Slow-Wave Structures for Traveling-Wave Tubes

This paper presents a novel 3-D finite-element modeling technique for the arbitrary lossy slow-wave structure (SWS) of a traveling-wave tube (TWT). By using this technique, we can accurately and quickly calculate not only dielectric losses but also conductivity losses of the SWS. In this modeling technique, a new frequency-specified eigenmode analysis (FSEA) for SWSs is proposed and utilized. Unlike the traditional phase-advance-specified eigenmode analysis for SWSs, which has to solve a nonlinear generalized eigenvalue problem (GEP), the new FSEA approach only needs to solve a linear GEP and is capable of obtaining the attenuation constant more accurately and directly without any postprocessing when simulating the lossy SWSs. Moreover, to further significantly improve the efficiency of modeling lossy SWSs, three advanced techniques are introduced in the standard implicit restarted Arnoldi method (IRAM) and an improved inexact IRAM is proposed. By simulating many practical SWSs, the accuracy and highly efficient performance of this modeling technique have been validated. It is shown that this modeling technique would be very useful to design a low-loss SWS for high-efficiency TWTs.

Some Slow-Wave Structures for Traveling-Wave Tubes

A comparison of four slow-wave propagating structures for traveling-wave tubes is made. Recent experimental performance of several types of tubes using two of these circuits is given. Amplifier performance of helix tubes at 10,000 Mc, and wide-tuned oscillator performance (1.5 to 1) with second-harmonic output around 20,000 Mc are described. The analysis, construction, and performance of a 10,000-Mc disk-loaded-rod tube are presented. Apertured-disk and spiraled-waveguide structures are discussed briefly and compared with the helix and disk-loaded rod.