Design and development of radial input cavity with coupler for inductive output tube

This paper presents the design and electromagnetic analysis of a radial-type input cavity structure for a 350 MHz high-power Inductive Output Tube (IOT), with a focus on developing and validating a novel analytical design methodology. Unlike conventional approaches that rely extensively on numerical simulations, the proposed analytical framework enables precise cavity design and optimization with minimal dependence on computationally intensive tools. This methodology offers enhanced design flexibility, faster prototyping, and deeper physical insight into the cavity behavior. The input cavity, along with a coaxial loop coupler engineered for efficient power injection and minimal reflection, was initially designed using the proposed analytical approach and subsequently verified through full-wave electromagnetic simulations and experimental cold-test measurements. A comprehensive sensitivity analysis was conducted to determine permissible mechanical tolerances in the fabricated structure. The fabricated prototype demonstrated excellent agreement with both analytical and simulated results, thereby validating the accuracy and robustness of the proposed design methodology. This work contributes a practical and efficient alternative to simulation-driven design for high-efficiency, high-power vacuum electron devices, particularly beneficial for the development of next-generation IOTs.