Analytical theory of microwave generation in vircator

In this paper, the mechanism of microwave generation in vircator is studied analytically, the formula of the small signal gain and the scaling law of the saturated power are given. The conclusion is that the coherent radiation in vircator is generated by the modulated electron current reflected from the virtual cathode. When the injection current is slightly larger than the first critical current, there is the highest radiation gain region, but the reflective current is smaller; when the injection current is slightly larger than the second critical current, there is a high radiation gain region, the reflective current is large too.