The propagation properties of an electron beam whose energy and current are simultaneously premodulated at the cathode are investigated by computer simulation using the two-dimensional particle-in-cell code, MAGIC. The simulation is carried out to investigate the influence of the initial energy modulation and phase difference between current and energy modulation. With appropriate initial energy modulation, amplitude of the downstream current modulation can be kept as high as the initial modulation level. Appreciable growth of high harmonic components is observed as the electron beam debunches. The maximum amplitude of the fundamental mode (m = 1) occurs at the propagation distance, where all the other modes vanish or have a very small amplitude.