Interaction Structures for Narrow-Band Millimeter-Wave Communications TWTs.

Abstract : This program was devoted to the investigation and development of new slow-wave interaction-structure technology benefiting narrow-band non-helix TWTs for millimeter-wave space-communications application. One recently introduced group of inherently narrow-band structures uses a one-piece copper-slab ladder enclosed in various simple ways to yield the equivalent of a chain of cavities with staggered or in-line, magnetic or electric coupling between them. A major objective is to assemble only a few pieces, regardless of the number of cavities in the chain. This objective also applies to the narrowest-band embodiments of a recently introduced novel slow-wave interaction-structure approach--'Comb-Quad'--likewise promising to alleviate fabrication difficulties, better retain dimensional precision and reduce costs relative to conventional axially stacked coupled-cavity chains at a given frequency such as 44 or 94 GHz. These new structures are mechanically and thermally robust, low in attenuation, and in particular offer electrical equivalence without sacrifice of interaction impedance. The narrow-band design evaluations were based on analytic techniques and scale-model cold testing. The circuit aspects investigated included dispersion, rf fields and currents, attenuation, interaction impedance extraneous modes and passbands, thermal effects, actual-size fabrication techniques, and the effects of several categories of geometric imperfection.