Patent GB-647955-A (GB)
Title: Improvements in or relating to cathode ray tube apparatus
IPC: G01S13/524
Filed: 1947-08-06
Abstract: 647,955. Radio-location ; storage tubes. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. Aug. 6, 1947, No. 21481. Convention date, Aug. 30, 1946. [Class 40 (vii)] [Also in Group XL (a)] In a storage tube, a first signal is stored on the target plate by the scanning beam, the potential of the plate is then varied by reference to a fixed potential by a second signal during a second scanning of the plate so that the returning electron beam is modulated only if the two signals are unlike, and the target elements are then restored to a predetermined potential in order that the cycle may be repeated. An image-orthicon tube 21, Fig. 1, used in a radio-location system, has a screen electrode 23 adjacent to a glass mosaic 22, which is scanned by a low-velocity beam from the gun 26 so that the returning beam will be modulated in accordance with the potentials on the mosaic elements. Secondary electrons released from the first anode 28 by the modulated beam are directed by a " persuader " ring 39 to an electron multiplier comprising secondary emitting electrodes 41-44 and an output electrode 46. The tube is further provided with a coil 33 for aligning the beam, a focusing coil 32, a ring- shaped electrode 31, and a photo-electric cathode 24 electrons from which can be focused on to the mosaic by electrodes 37, 38. Pulsemodulated oscillations are fed to the transmitter 16 from an oscillator 10 through an amplifier 11 which is connected to a pulse generator 12 through a modulator 13. The receiver is connected to a mixer 18, the output signal of which will depend upon the phase relationship between the received signal and the local oscillations from the generator 10. The signal is applied through a condenser 57 and an amplifier 58 to the vertical deflecting plates of an oscilloscope 59. The steady bias of 1¢ volts on the signal grid 23 is swung from 1 volt during the first scan to 2 volts during the second by a square-wave generator 53 which is eontrolled synchronously with the pulse generator 12. During the first scan by the lowvelocity beam which is deflected by a magnetic yoke 34, connected to a saw-tooth or spiral deflection circuit operated synchronously with the generator 12, the signal on the grid 23 is reproduced in inverted form on the mosaic elements ; a blocking voltage on the oscilloscope grid from the circuit 63 prevents the signal produced by the modulated returning beam from being recorded. During the second scan of the mosaic, when the second signal is applied to the grid, the returning electron beam will be modulated in accordance with any difference between the two successive signals and this difference will be reproduced in the oscilloscope. At the end of the second scan, the mosaic elements are restored to the potential of the grid by electrons from the cathode released by a flash from the light source 54 which is controlled in synchronism with the pulse generator. In a modification, Fig. 1A (not shown), the signals are applied to the cathode. In a further form, Fig. 8 (not shown), the low-velocity beam is density modulated by signals applied to a control grid. To produce on the mosaic elements an inverted electrical pattern, the first signal is applied to the control grid through an inverting amplifier and the second signal through the usual amplifier ; the square-wave generator used for varying the voltage of the grid, associated with the mosaic, is used for blocking the amplifiers alternately during each scan. Modifications of the above arrangements are described with reference to Figs. 8, 9 (not shown), whereby the image orthicon tube is used for storing a signal on the mosaic during the first scan which is subsequently reproduced in the returning beam during the second scan for reproduction in an oscilloscope.