A Novel Gap-Groove Folded-Waveguide Slow-Wave Structure for G-Band Traveling-Wave Tube

Abstract

In this paper, a novel gap-groove folded-waveguide slow-wave structure (SWS) for high-efficiency G-band travelingwave tube (TWT) is presented. In this novel tube, a sheet electron beam passes through the small gap between a bed of nails and a folded groove realized in a metallic plate. The bed of nails and the metallic plate form a high impedance structure-perfect electric conductor parallel plate waveguide, which prevents the fields from leaking transverse to the propagation direction. The phase velocity of the proposed SWS has been analytically calculated and the results show good agreement with those obtained using Eigenmode solver of computer simulation technology (CST). Meanwhile, the simulation results indicate that the interaction impedance of the proposed SWS is considerably higher than the conventional folded-waveguide SWS. Furthermore, employing a proper phase velocity taper in the end section of circuit leads to increasing the efficiency of the proposed TWT. According to Particle-in-cell simulations performed by the CST Particle Studio, the designed TWT can generate a peak power of 225 W at 220 GHz, corresponding to the maximum gain and efficiency of 42.7 dB and 14.9%, respectively. IndexTerms-Folded waveguide (FW), gap-groove waveguide (GGW), slow-wave structure (SWS), travelingwave tube (TWT).

Half-Height Pin Gap Waveguide-Based Slow-Wave Structure for Millimeter Wave Traveling-Wave Tubes

“…Several of these SWSs have been demonstrated via CNC micro-machining and LIGA (German acronym for Lithography, Electroplating and Molding) [5]- [7]. In this context, alternative waveguiding technology, based on the use of periodic arrangements, such as electromagnetic bandgap structures, have also been recently proposed to introduce single mode of operation in oversized structures and flexibility of design with functionalities integration [8]- [10]. For instance, in [8], a simple and scalable solution for wide, above the cutoff, beam tunnel designs was presented.…”

Half-Mode Waveguide Based on Gap Waveguide Technology for Rapid Prototyping

“…Interesting theoretical work was presented in the past addressing this half-mode configuration [9], [10], but, to date, at least to the knowledge of these authors, its actual possibilities in manufactured GW devices have not been studied yet. In this letter, we demonstrate the feasibility of the concept by means of a narrowband one-to-two power divider and a curved waveguide.…”

Gap waveguides for millimeter wave slow wave structures

“…In addition, as compared to conventional metal waveguides, gap waveguides control wave propagation through the use of a contactless parallel high impedance surface (an artificial magnetic conductor) and conducting plate. Under the condition that the gap is less than a quarter of the wavelength, no electromagnetic propagation is allowed through this structure unless some guiding element is included in the form of a ridge or a groove waveguide, for example [3][4]. The increased flexibility of this technology with respect to what presented in [2] can be exploited to facilitate the design and realization of slow wave structures in the millimeter wave range.…”