Using whole structure modes in the large-signal modeling of TWTs with arbitrary slow-wave structures

We describe a new formulation for the electromagnetic fields in an arbitrary slow wave structure that can be used in the 2D large-signal modeling of beam-wave interaction. The main idea is to represent fields in the portions of the structure not occupied by the beam as a superposition of whole structure modes. This approach generalizes that based on circuit models, such as the Curnow model. Our plans include development and implementation of this new formulation in a large-signal code to allow efficient computer modeling of a broad class of microwave amplifiers, especially targeting devices used in the millimeter and sub-millimeter wave-length ranges.