Attenuation Theory of the Attenuator-Coated Helical Slow-Wave Structure

Based on the field analysis method, tape-helix model was used to analyze the helical slow wave structure considering the helix turns to be effectively shorted by the resistive attenuator coating on dielectric helix-support rods. A smoothed out effective surface resistivity accounted for the resistive coating on discrete support rods. The attenuation and phase propagation constants as well as the interaction impedance of the structure were obtained by the present attenuation theory. In the meantime, the expression of the effective surface resistivity of attenuation coating was derived. At last, the dependence of the attenuation constant, phase propagation constant and interaction impedance of the attenuator-coated discrete dielectric helix supports on the surface resistivity of coating was accurately predicted.