Amplifiers having at least one tube quadrupole or tube adler

摘要

906,178. Automatic gain control. ENGLISH ELECTRIC VALVE CO. Ltd. May 8, 1961 [Sept. 27, 1960], No. 33188/60. Class 40 (5). The invention relates to an amplifier employing a quadrupole electron beam tube, in which an electron beam from electron gun 1 is constrained by an axial magnetic field in its passage down the tube to collector electrode 5. The beam first passes between input coupler electrodes 2, in which it is modulated by the signal to be amplified, then between the quadrupole electrode system 3 to which a pump frequency approximately equal to the signal frequency is applied, and finally between output electrodes 4 from which an amplified signal is obtained. The input signals cause the path of the electrons to become helical, and due to the amplification in the tube, the amplitude reached at the output electrodes 4 is sufficient for electrons to actually strike these electrodes, so causing overloading of the tube, before a correspondingly large amplitude is reached at the input electrodes 2. To allow the tube to handle a larger input signal, the output, after amplification in succeeding stages 8, is applied to a rectifier 10, the D.C. output of which is added to the positive bias applied over resistor 11 from terminal 12 to the electrodes 3. The bias from source 12 also acts as a delay voltage on diode 10; when this is exceeded, the D.C. bias on electrodes 3 is increased, increasing the speed of the electrons through the quadrupole electrode system, and so reducing the gain in the tube. A larger input is then permissible before overloading sets in. The bias potential on terminal 12 may be made variable.