Equivalent circuit analysis of a planar helix slow-wave structure for application in high frequency traveling-wave tubes

A planar helix slow-wave structure comprised of a pair of unidirectionally conducting screens was analyzed for its equivalent circuit parameters. These parameters were interpreted for the structure dispersion characteristics and, subsequently, the structure interaction impedance and the Pierce's gain parameter of a planar-helix TWT. For identical situations with respect to the structure parameters, the present analysis of the planar helix predicted a lower phase velocity, higher interaction impedance, and, consequently, a larger Pierce's gain parameter and hence a greater promise for a higher device efficiency over a wide frequency range than the conventional circular helix.