Patent ID: 6495961
Filing Date: 2002-12-17
Classification: H01J

Abstract:
A power supply for the cathode-to-collector beam of a travelling-wave tube including a cathode, a body connected to ground, and a collector, said power supply comprising:a first voltage source including a negative terminal, and also including a positive terminal coupled to said collector of said travelling-wave tube; electrical coupling means coupled to said negative terminal of said first voltage source and to said cathode of said travelling-wave tube, for thereby establishing a cathode-to-collector voltage of said travelling-wave tube near said first voltage; a controllable impedance including a first terminal coupled to said ground and also including a second terminal, said controllable impedance further including a control terminal responsive to a control signal for controlling the impedance between said first and second terminals of said controllable impedance, said controllable impedance comprising (a) a resistor having one end coupled to said ground; (b) a first controllable solid-state device including first and second electrodes, and a control electrode to which a control signal can be applied for controlling the impedance between said first and second electrodes, said first controllable solid-state device having said first electrode coupled to said ground by way of said resistor, and also having said control electrode coupled to said control terminal of said controllable impedance; (b) at least two additional controllable solid-state devices, each said additional controllable solid state device including first and second electrodes and a control electrode to which a control signal can be applied for controlling the impedance between said first and second electrodes, said additional controllable solid-state devices being in a cascade in which each such cascaded solid-state device, except those at the ends of said cascade, has its second electrode coupled to the first electrode of the next adjacent one of said additional controllable solid-state devices in said cascade, and in which the first electrode of that one of said additional controllable solid-state devices at a first end of said cascade is connected to said second electrode of said first controllable solid-state device, and in which the second electrode of that one of said additional controllable solid-state devices at a second end of said cascade is connected to said second terminal of said controllable impedance; and (c) means for equalizing the voltages applied between said first and second terminals of said additional controllable solid-state devices; a second voltage source including a negative terminal coupled to said collector of said travelling-wave tube and a positive terminal connected to said second terminal of said controllable impedance; and a cathode-to-ground voltage controller coupled to said cathode of said travelling-wave tube, to said ground, and to said control terminal of said controllable impedance, for controlling said control signal in a manner which tends to maintain the voltage between said ground and said cathode of said travelling-wave tube constant.