Comments on "Numerical analysis and design for high-performance helix traveling-wave tubes"

Tsutaki et al. recently established a new design method based on an analytical technique to consider the influences of the tape width, dielectric, and shield barrel in the helix slow-wave circuit. However, there are numerous mistakes on the equations that will make it impossible for a reader to make use of these equations for analytical tools. Here, a few obvious mistakes are pointed out so that corrections can be made to several equations.