Coupled-mode analysis for nonuniform crossed-field drift beams

Coupled-mode theory is used to describe the propagation of waves on a nonuniform crossed-field beam in a drift region. The nonuniformity considered in this paper is due to potential variation along the beam. Numercial solutions are obtained for the normal-mode amplitudes for two types of potential variation, namely, linear and exponential. It is shown that the coupling between the modes, which is due to the potential variation, can be used to reduce the noise figure of crossed-field amplifiers.