$W$ -Band Multiple Beam Staggered Double-Vane Traveling Wave Tube With Broad Band and High Output Power

Abstract

A design study for a high-power, high-efficiency, high-growth-rate wideband traveling wave tube (TWT) in W -band using a staggered double-vane slow-wave structure (SWS) combined with three plan alignment pencil beams is described in this paper. The electromagnetic characteristic simulation shows that it has a wide bandwidth, high interaction impedance (about two to three times higher than those of the same structures with the sheet beam scheme), and a more simply designed input/output coupler. 3-D particle-in-cell simulations predict that the TWT can produce over 2000 W of output power from 91 to 95 GHz just using a 52-period two section SWS with a total length of 70.3 mm when the voltage and current of three pencil beams are set to 22 kV and 140 × 3 mA, respectively. The maximum peak output power is about 2256 W with a corresponding gain of 43.5 dB and an electronic efficiency of 12.2% at 94 GHz. The 3-dB bandwidth can be achieved at about 15 GHz with an instantaneous relative bandwidth of about 15.9%. Finally, the comparisons of sheet beam, multiple beam, and single pencil beam staggered double-vane TWT are presented and analyzed.Index Terms-Interaction impedance, multiple beam, slow-wave structure (SWS), staggered double vane, traveling wave tube (TWT), W -band.

Multiple-beam and double-mode staggered double vane travelling wave tube with ultra-wide band

“…Thus, we can calculate the value of synchronous phase velocity and the length of the single period SDV-SWS p by using (1) and (2), where v p is the phase velocity of electrons, c is the speed of light in vacuum. Then, the effects of each structure parameters on dispersion characteristics for SDV-SWS can be studied thoroughly, and the results are similar to our previous work 11 . As l increases, the whole phase velocity decreases; as h increases, the phase velocity of high frequency decreases but that of low frequency keeps the same.…”

“…In this paper, to further improve the bandwidth, keep the high output power and avoid the serious problems of sheet beam formation and long distance transportation, instead of using the only fundamental single mode to match with the electron beam, the fundamental double-mode SDV-SWS with planar alignment three-pencil beam in W-band is studied thoroughly. It is found that the beam-wave matching band indeed increases as twice compared to our previous work 11 . Also, the interaction impedance is also about two times higher than that of sheet beam SWS in the same band.…”

“…Finally, 3D PIC simulation shows that it can obtain a high output power of nearly 2120 W at 94 GHz with a two-stage 51-period SWS-TWT, the gain of 42.5 dB and the efficiency 10.7%. The 3 dB bandwidth about 29 GHz from 81 to 110 GHz can be achieved, which is almost twice than that of our previous work (15 GHz) 11 . Thus, our double-mode, two-stage and planar alignment three-pencil beam SDV-TWT indeed has good performances of high power and broadband in millimeter and terahertz band.…”

“…1, which can form a strong symmetric axial electric field distribution along the direction of electron movement 16 . Also, compared to sheet beam, the planar alignment pencil beam tunnels can constrain the electric field better to increase the axial electric field 11,17 . So, sheet beam tunnels are replaced by three pencil beam tunnels as is shown in the figure, where l is the width of the vane, h is the height of the vane, p is the length of the single period SDV-SWS, g is the distance from the upper vane to the lower vane, tr is the radius of the pencil beam tunnel and d is the distance between the edges of two adjacent beam tunnels.…”

“…Moreover, compared to sheet beam tunnels, the pencil beam tunnels have a much stronger E z . That can be explained as pencil beam tunnels can constrain the electric field better in a smaller space to form the stronger field, so the interaction impedance obtains a big increase 11 .…”