Recent Developments in Inductive Output Amplifiers,

An inductive output amplifier is an RF device in which an emission-gated electron beam induces RF fields in an output circuit by means of displacement currents, not convection current. Emission-gated electron beams experience strong interactions when traversing a resonant or synchronous electromagnetic field, and this strong interaction is responsible for both the interesting nonlinear physics and the attractive efficiency and compactness of emission-gated amplifiers. Field emission cathodes, due to their extremely low electron transit time and high transconductance, offer the opportunity to extend the advantages of spatiotemporal modulation into C and X bands. This paper presents design criteria for the joint optimization of the field emission array structure and the ltF input and output circuits of inductive output amplifiers. We find that while output circuits yielding net efficiencies of 50 or greater are well within the state of the art, the gain is likely to be moderate 10 to 20 13. With todays FEA performance, a desirable operating regime is achievable, yielding a new class of compact, highly efficient, and moderate-gain power booster amplifiers.