Two Novel Kinds of the $G$ -Band Travelling-Wave Tubes With Multiple Gap-Groove Folded-Waveguides

In this paper, two kinds of the travelling wave tubes (TWTs) with multiple gap-groove folded-waveguides are investigated. In these kinds of tubes, the sheet electron beam passes through the small gap between a bed of nails and the 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. Therefore, multiple GGFWs can be placed near each other with no need to any separator. First, a simple G-band TWT with two GGFWs is designed, and the electromagnetic properties of the propagating even and odd modes, versus the distance between two grooves, are studied. Meanwhile, the PIC simulation performed by the particle studio of computer simulation technology indicates that the optimum performance of the tube will occur when the distance between two GGFWs is 0.51 mm, and the odd mode is propagated. In this case, each circuit of the proposed double slow wave structure TWT can deliver 278 W, which is corresponding to maximum gain and efficiency of 43.6 dB and 18.3%, respectively. Afterward, according to these obtained results, a low voltage, relatively high efficiency and miniature log-periodic GGFW TWT with 30 circuits, is presented. The PIC simulation shows that this kind of TWT can deliver 36 W, which is corresponding to the efficiency of 9%.