Effect of the electron beam modulation on the sub-THz generation in the vircator with the field-emission cathode

In this paper, we focus on the numerical investigation of the vircator with a controlling emission from a field-emission cathode. The external harmonic signal is added to the accelerating electric field in the beam formation region and effects on the beam emission process leading to the electron emission modulation. As a consequence, the beam is injected into the drift chamber of the vircator being density-modulated. The strong influence of the modulation parameters (modulation depth and frequency) on the characteristics of virtual cathode oscillations has been discovered. We have shown that the tuning of the modulation frequency to the harmonics of the basic frequency of virtual cathode oscillations leads to the considerable power increase of its higher harmonics in the output spectrum.