Phase-shifted double vane circuit (Barnett-Shin TWT) for ultra-wideband millimeter and submillimeter wave generation

A novel slow wave vacuum electron device circuit, the so-called “Barnett-Shin traveling wave tube (TWT) circuit”, which consists of a half-period-staggered double vane array and a high aspect ratio sheet beam, has been conceived for high power millimeter and submillimeter wave amplification/ oscillation applications requiring extremely wide bandwidth as well as compact size and light weight. Particle-in-cell simulations based on a finite-difference-time-domain algorithm have shown that this circuit has a very wide intrinsic bandwidth (in excess of 50GHz around the operating frequency of 220GHz) with a moderate gain of 13dB. Also, the saturated electronic conversion efficiency is 3 ∼ 5.5%, which corresponds to radiation power of 150 ∼ 275W, assuming a beam power of 5kW. Of particular importance, this structure is based on TE-fundamental mode interaction, which can avoid complex overmoding instability usually causing spurious signal oscillations in the conventional high aspect ratio structure. Moreover, this planar circuit has a simple two-dimensional geometry so as to be thermally and mechanically robust as well as compatible with conventional micro-fabrication techniques. This concept will open promising opportunities in potential applications of versatile electronic devices to the millimeter and submillimeter wave region.