Schutzanodnung für Wanderwellenröhren

摘要

A travelling-wave tube (TWT) for a satellite communication system includes a cathode current regulator which compares a sensed IK signal with a cathode current reference to form an cathode current error signal, and controls the cathode current in response to the cathode current error signal. Helix arc protection is provided by a helix current shut-down, which compares the helix current with a particular reference, and shuts the TWT supply down when helix current flows. Desirable high efficiency TWTs have a small input drive range between maximum TWT output and a defocussed condition, in which beam current flows in the helix. Sudden changes in path attenuation may result in an RF overdrive condition, and cause helix current flow, and undesirably shut down the TWT. A helix current limiter senses the helix current, and compares it with a reference which represents less helix current than that which causes shutdown, to produce a helix current error signal. The helix current error signal adjusts the cathode current reference, to thereby reduce the cathode current in a feedback manner, to thereby tend to maintain the helix current constant at a value below the shut-down helix current.