Difference in Cutoff Frequencies of TE Modes between Approximate and Analytic Solutions in the Co-axial Structure as a Single-phase GIS

Abstract

This paper described difference in cutoff frequency of TEm1 modes between the conventional approximate solution followed by the radii of the inner and outer conductors and the analytic solution in the co-axial structure as a single-phase GIS. The analytic solutions were calculated by the Bessel function based on the boundary condition and confirmed the validity by the FD-TD method in the same size structure. As a result, the approximate solution for the TE11 mode is available while the higher modes above TE21 modes are not available when the difference in the inner and outer conductor radii was increased. Thus, a new approximate equation is introduced, which allows us to obtain more precise result rather than the conventional one.