The helix coupled vane and helix coupled bar circuits belong to a new type of slow wave structures for high power crossed-field amplifiers. These circuits are characterized by their very wide bandwidth

relatively high coupling impedance as well as high average power-handling capability

and hence obtain wide applications. Both multi-conductor transmission line method and equivalent circuit method are used to carry out theoretical analysis of these SWSs. Analytical expressions for dispersion characteristic

coupling impedance and transverse field distribution are derived; the effects of each dimensional variation on dispersion characteristics and coupling impedance are given on the basis of a large quantity of computer results. A comparison between computed and experimental values indicates that results given in this paper are sufficient for engineering design purpose.