Dual Helix Slow Wave Structure Cold Characteristics Analysis Using a Structural Model for Traveling-Wave Tube

In this paper, a simplified model for dual helix cold characteristics (phase velocity and interaction impedance) analysis is presented. The model comprises a conventional circular helix with the center being at a distance of its radius from the envelope center. The cold characteristics of the proposed model are calculated using the sheath field analysis approach. Since the centers of the shifted helix and theenvelope of the proposed model are not coincident, the addition theorem is used for electromagnetic equations. Compared to simulation results of the dual helix in the frequency range of 1-6 GHz, the calculated results of the proposed model show the accuracy ranges of more than %94 and %87 for the phase velocity and interaction impedance, respectively.