This paper presents a technique to reduce the standard single-pitch helical model when performing a full-wave analysis of helical slow-wave structures (SWSs). The technique
makes use of azimuthally periodic boundary conditions applied to the conventional helical SWS; the ternary angular symmetry of its dielectric rods allows reducing the standard computational domain by two thirds. It has been demonstrated that this method, as implemented with a commercially available simulator (highfrequency structure simulator), has no impact on the stability and accuracy of the cold parameters but allows a significant reduction of simulation time, which increases with the accuracy of the results. The proposed technique is therefore perfectly suitable for the accurate modeling of complex geometries and is expected to be particularly attractive for optimization analyses and applications in which accuracy and short simulation time are main concerns.