Modeling of a 1700-MHz cluster cavity of planar triodes

The authors present the modeling and design of a 1700-MHz cluster-cavity vacuum tube amplifier. They used a three-dimensional finite-difference code to characterize the modes that the structure would support and to modify the cavity design in order to select the desired mode. The characteristics of the tube are described, including performance predictions. The feasibility of a resonant structure is considered that supports a combination of four planar triodes without external combiners. Only the output resonator is described. The design locates the planar triodes in sections of rectangular waveguide with movable end walls that provide each tube with an independent loading adjustment. In addition, the waveguide sections help to increase the resonant frequency of the dipole and quadrupole modes with respect to a cylindrical structure of comparable size. A number of planar triodes can be combined in a resonant structure to increase the power level of vacuum tube amplifiers at high frequencies, resulting in a low-cost source of RF for medium-power applications.<>