Vane-Loaded Planar Helix Slow-Wave Structure for Application in Broadband Traveling-Wave Tubes

Abstract

Dispersion control of a planar helix slow-wave structure (SWS) using vane loading for applications in travelingwave tubes has been studied. The addition of metal vanes and coplanar ground planes to the planar helix structure has been investigated with the help of simulations aimed at achieving low or negative dispersion. It is shown that, similar to the case of circular helix, the addition of metallic vanes to the planar helix can produce a flatter dispersion curve or negative dispersion characteristics. Furthermore, it is shown that even stronger dispersion control can be achieved by the use of metal vanes together with extended coplanar ground planes on the dielectric substrates that support the planar helix. As a proof of concept, one of the designs of the planar helix SWS including metal vanes and operating at S-band frequencies has been fabricated and tested; the measured phase velocity results match the simulation results very well.Index Terms-Broadband traveling-wave tubes (TWTs), coplanar ground plane, planar helix, slow-wave structure (SWS), vane loading.

Wideband Power Combining of Four Microfabricated W-Band Traveling-Wave Tubes

“…Fig. 14 presents a typical result obtained from the PIC simulations using CST Particle Studio [26]. Fig.…”

“…The dispersion curve is different from a normal helical SWS in which phase velocity falls with increasing frequency. Such a behaviour (including negative dispersion) is seen when the metal shield comes rather close to the SWS and there are also CPW ground planes[26]. The coupling impedance shown in Fig.3(b) has a relatively high value of about 23.6 Ohms at 100 GHz.…”

Application of planar helix slow-wave structure in backward-wave oscillators

“…Other than metal vanes, coplanar ground planes in PH-SEC also have significant effect on dispersion. The simulation and measurement studies show that stronger dispersion control can be achieved from a PH-SEC by using metal vanes together with extended coplanar ground planes [74]. The studies on dispersion control lead to the development of microfabricationcompatible PH-SEC SWS shown in Fig.…”

“…Three types of metal wanes namely T-shaped, solid, and thin vanes have been found very effective for circular helix. The impact of such metal vanes on the characteristics of fundamental space harmonics in PH-SEC has been studied [74]. The studies show that, similar to the case of circular helix, a flatter dispersion curve or negative dispersion characteristics can be obtained from PH-SEC using metal vanes.…”

Development of carbon nanotubes for vacuum electronics application

“…As for high speed Ka-band communication, a small diameter (< 1mm) of Slow-Wave Structure (SWS) is needed [12], thus driving increased demands for miniaturized TWTAs. Besides, in a study reported by our research group, a Planar Helix-SWS (PH-SWS) has been proposed to be fabricated by using silicon-based microfabrication techniques [13]. Furthermore, in the attempt to incorporate sheet beam into the PH-SWS TWTA, the design of a sheet-beam electron gun is generated [14].…”