Using CST Microwave Studio,the dispersion characteristics of a staggered double rectangular grating slow wave structure(SDRG SWS)is calculated,and the structure parameters of SDRG SWS for a 0.22THz(D band)traveling wave tube(TWT)are determined based on the dispersion data.Then phase velocity re-synchronization techniques are applied in D band TWT based on SDRG SWS,and four D band TWTs which have different period configurations are simulated by CST PIC solver.The results demonstrate that the phase velocity r...