CALCULATION OF BEAM LOADING USING THE INDUCED-CURRENT METHOD IN PASSIVE CAVITIES

Quantitative knowledge of beam loading and detuning is necessary for t he prediction of the bandwidth and operating frequency of an electron device that has resonant interactions. We present a method for calcula ting the loaded Q and beam detuning of a passive (gain or idler) cavit y in an electron device. The method is based on the determination of i nduced current by a technique often referred to as Ramo's theorem. We use the induced current in conjunction with a lumped equivalent circui t representing the cavity. This leads to a solution for the self-consi stent cavity fields. Although the induced-current expression is usuall y developed from low-frequency models, we show that Ramo's theorem is valid for high-frequency, steady-state analysis when the unloaded pass ive cavity Q is high. We use the method to calculate the loaded Q of t he passive cavity of a new type of gyro-resonant electron device, the magnicon.