Some aspects of the design of a helical coupler for a travelling-wave tube operating in the 2 Gc/s band

The paper describes the development of a helical coupler designed for use with travelling-wave tubes operating in the 1700-2300 Mc/s band. The theory of operation of helical couplers is briefly summarized, and the design and construction of the coupler are then dealt with. An outline of the measuring techniques employed in the course of its development is also given. The final design leads to an input v.s.w.r. better than 1.3 and a directivity better than 4dB over the required frequency band.