Theoretical Analysis of Conductivity and Dielectric Attenuation in Millimeter-wave TWT Helical SWS
理论分析毫米波螺旋线行波管慢波系统导体和介质损耗

Conductivity and dielectric attenuation in millimeter-wave TWT helical Slow-Wave Structure (SWS) are analyzed by a stratified dielectric helix tape and a 3D electromagnetic model. In tape model, the imaginary part of complex propagation constant is considered as dielectric attenuation, and the conductivity losses are obtained by discontinuous surface current on metal helix and envelope. For 3D electromagnetic model, the RF losses of SWS are deduced through a quality factor and stored energy in a periodic structure with finite conductivity of helix and envelop and loss tangent of supported rods. An analysis of a Ka helical SWS shows that the conductivity loss of helix and dielectric attenuation of supported rods are greater than conductivity loss of envelope, the dielectric attenuation is linear with ceramic loss tangent and can not be neglected in millimeter wave band.