Asymptotic Theory of High-Efficiency Converters of Higher-Order Waveguide Modes into Eigenwaves of Open Mirror Lines

Based on the Debye asymptotic for Bessel functions, we develop an analytical theory of high-efficiency converters of higher-order waveguide modes into eigenwaves of open mirror transmission lines. Simple analytical formulas for the parameters of the basic types of mirror lines are derived. Direct relationship between the nonequidistance of mode wavenumbers, the diffraction lengths of the Brillouin wave beams, and the lengths of converters for oversized waveguides is shown. The results of numerical calculations for some converters are presented for comparison.