Relationship between axis length and beat-wave wavelength in double-bent circular waveguide TM01-TE11 mode converter

The axis length and the beat-wave wavelength in double-bent circular waveguide TM01-TE11 mode converter are analyzed, keeping the axis of the output port parallel to that of the input port and keeping the two curvature radii equal. It is proved that the axis length is directly proportional to the beat wave wavelength and the ratio of the axis length to the beat-wave wavelength is 2/2. The lower limit of the pass band is obtained by theory and simulation when the simulated power conversion efficiency exceeds 98%, which is 1.07 times of that of the TM01 mode cut-off frequency.