The gain of travelling-wave ferromagnetic amplifiers

The paper describes a general perturbation method for determining the gain of travelling-wave ferromagnetic amplifiers. By use of the method, the gain is determined for an amplifier employing a circular waveguide and an axial ferrite rod of small cross-section. The efficiency of such an amplifier is shown to be low, and a practical version would demand the use of larger rod cross-section and/or a slow-wave structure. Other possible waveguide configurations for amplifiers are briefly mentioned, together with certain practical aspects of construction.