Microwave tube with improved output signal extracting structure

A helix slow-wave circuit type travelling wave tube which includes an evacuated envelope containing an electron gun means located at one end thereof for providing a beam of electrons and a collector means located at the other end of the evacuated envelope for collecting the electron beam provided by the electron gun means, a helix slow-wave circuit located in the evacuated envelope in such a manner that the electron beam passes through the slow-wave circuit to the collector, means at an upstream side of the electron beam for applying a microwave signal to the slow-wave circuit, and means at a downstream side of the electron beam for extracting an amplified output signal from the slow-wave circuit, said circuit being characterized in that the output signal extracting means comprises a coaxial line including an outer conductor which is air-tightly fixed at one end thereof to the evacuated envelope and an inner conductor having one end connected to one end of the helix slow-wave circuit at an angle to the center axis of the electron beam;

• an output waveguide which is air-tightly fixed to the other end of the coaxial line outer conductor so that the other end of the coaxial line inner conductor extends into the output waveguide;
• a resistive ridge formed on an inner wall surface of the output waveguide to oppose the inner conductor of the coaxial line, a dielectric hollow cylindrical member positioned in the output waveguide to surround the other end of the coaxial line inner conductor, the cylindrical member being air-tightly fixed at its one end to the inner wall of the output waveguide and at its other end to the ridge formed in the output waveguide, and the other end of the coaxial line inner conductor being connected to the ridge formed in the output waveguide.