The Comb-Type Slow-Wave Structure for TWM Applications

The comb-type structure has been used successfully as a slow-wave structure for traveling-wave masers (TWM). 1 In a T W M the smallsignal gain in db is inversely proportional to the group velocity. Generally the gain obtainable from present maser materials is small. Therefore, a great deal of effort in developing a T W M is concerned with deriving a comb structure design with small group velocity at the frequency of interest. Both the group velocity and the passband of the comb structure can be found from the diagram. The shape of the diagram of the comb structure loaded with "masing" crystal depends very critically on the various dimensions of the structure as well as of the crystal. In this paper, an analysis of the comb structure will be presented. It should serve as a guide for a reasonably accurate determination of the dimensions of the comb structure, of the active maser material and of other dielectrics which give rise to a required w-/? diagram. Some additional * This work was supported in p a r t by the U. S. Army Signal Corps under Contract No. DA 36-039-SC-89109. 1035