Tapered Cavity as Input Cavity in a High-Power Inductive Output Tube

A novel approach of introducing a tapered geometry to the radial re-entrant input cavity has been adopted in high-power inductive output tube (IOT) to enhance the quality factor of the cavity. The geometrical parameters of the cavity have been optimized to achieve the desired resonant frequency employing an analytical approach. Additionally, a coaxial loop coupler has been designed to efficiently inject input power into the cavity with minimal reflection. Performance parameters like <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i>-parameters and return loss of the tapered reentrant cavity have been evaluated and compared with the conventional radial re-entrant cavity without taper. The novel tapered cavity design yields an improved quality factor of ~3186 compared to a value of 2776 with the conventional design. Furthermore, a significant decrease in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${S} _{11}$</tex-math> </inline-formula> value from −26.3 to −37.74 dB indicates lower signal reflection in the tapered cavity compared to the conventional one. The optimized cavity has been fabricated and it has been observed that measurement results have a strong agreement with simulation results. Hence, this novel modification significantly contributes to advancing IOT designs for high-power RF applications such as particle accelerators, plasma heating, and communication systems.