A Signal Input Selective Device for a High-Current Relativistic Cherenkov Amplifier

Selective unidirectional excitation of a cylindrical waveguide through the lateral wall is investigated as applied to the signal input into a millimeter high-current relativistic Cherenkov amplifier. The ratio of the parameters of the input device has been found providing the maximum transformation of the fundamental mode of a rectangular waveguide into the unidirectional lower axisymmetric mode of a cylindrical waveguide. In the absence of Ohmic losses, the conversion efficiency reaches 97.5%. An input device adapted to the design of a 35.5-GHz amplifier is implemented with an efficiency of 75%.