Characterization of Ring-Bar and Contrawound Helix Circuits for High-Power Traveling-Wave Tubes

Theory and New Amplification Regime in Periodic Multimodal Slow Wave Structures With Degeneracy Interacting With an Electron Beam

“…Some other commonly used SWSs include comb structure [15], disk structures [16], interdigitated structures [17] and folded-waveguides for terahertz radiation [18], [19], among others. Metamaterial based slow-wave structures were proposed recently [20] by embedding subwavelength resonant elements inside waveguides, like ring-bars [21] or split-ring resonators [22], [23]. Typically at microwave frequencies, periodic structures are implemented as metallic obstacles or slots due to lower losses than in dielectrics and to the ability to sustain very large field gradients [24].…”

Studies on planar helical slow-wave structures for traveling-wave tube applications

“…The coupling impedance may increase or decrease as the period increases depending on whether the frequency range is below or above a certain 'cross-over frequency'. A similar effect has also been observed in[142] for the circular ring-bar structure. The cross-over frequency isshifted to the band-edge for b/a = 23.…”

“…In this sub-section, we study the effect of variations in L, ST, SW, BW, and VD (together with RD) on the phase velocity and coupling impedance for the RRB-SEC with cylindrical vias, in free space. The detailed dimensions of each structure are listed in Appendix C. In general, the nature of these effects is similar to that reported for the circular ring-bar structure [7] and [142]. having the same effect as reducing the perimeter for a given period.…”

Propagation of Degenerate Band-Edge Modes Using Dual Nonidentical Coupled Transmission Lines

“…Indeed, this property has been used to enhance coupling of the electron beam to RF waves in traveling wave tubes and BWO applications. Examples of coupled transmission lines include double helix [27], ring-bar [28,29] and ring-loop [30] etc. For these cases, the TL pair had identical lumped elements (L, C) and supports regular band edge mode only.…”