Electronic tubes such as tetrodes for very high frequency operation

Claim 1

A high frequency operating tetrode comprising: cylindrical electrodes arranged coaxially within a tight exhausted enclosure about the tube axis, including successively from said axis, an electron-emissive cathode, a control-grid, a screen-grid and an anode, input coupling means applying a high frequency input wave between said control-grid and said cathode, output coupling means extracting an output high-frequency wave between said anode and said screen-grid, tunable coaxial cavities including conductive cylindrical walls arranged coaxially about said axis and respectively connected to one extremity of the of the electrodes, a central conductive cylinder coaxially arranged about said axis and passing through said cathode, said central cylinder having a first extremity extending from said cathode towards said cylindrical walls and a second extremity extending from the cathode opposite the first extremity, a further conductive clyindrical wall establishing a coaxial cavity being coupled to said first mentioned extremity of the central cylinder and the second mentioned extremity of the central cylinder being coupled to the screen grid at one end and the opposite end of the screen grid being coupled to one of the cylindrical walls, and ring pistons movable aLong said coaxial cavities for providing their respective tuning, the ring piston movable along one of said coaxial cavities between the cylindrical wall coupled to the cathode and the cylindrical wall coupled to the first extremity of the said central cylinder being adjusted for ensuring a high-frequency short-circuit between said cathode and said screen-grid.