Patent GB-832986-A (GB)
Title: Improvements in or relating to cathode ray tube circuit arrangements
Inventor: PLAISTOWE DONALD LEOPOLD
IPC: G01S7/28
Filed: 1956-09-26
Abstract: 832,986. Cathode-ray tubes. MARCONI'S WIRELESS TELEGRAPH CO. Ltd. May 15, 1957 [Sept. 26, 1956], No. 29383/56. Addition to 812,635. Class 39(1). [Also in Group XL(c)] In a cathode ray circuit for storing and reading off stored information for use in a radio direction finder or radar apparatus the tube has a single electron gun, 1, 4, 5, 6, Fig. 1, a target including a plurality of discrete conductive strips 22, Fig. 2, arranged radially in a ring on one face of an insulating carrier 19, two concentric conductive, rings 24, 25 on the other face of the carrier, each ring having width of less than half the radial length of a strip, two concentric ring grids 20, 21 closely spaced in front of the screen, the radial width, of each grid being less than half the radial length of a strip, and four pairs of electrostatic deflecting plates 13, 14, 15, 16, two pairs 13, 14 being between the gun and outer grid 21 and the other two pairs 15, 16 being between the gun and inner grid 20 and two pairs of additional plates 10, 11, 12 (plate 10 preferably being common as shown) between gun and main deflecting plates, means for producing two equal amplitude voltage waves in quadrature at frequency #1 and applying them to two pairs of main deflecting plates 13, 14 respectively to rotate the beam at one speed, means for producing two equal amplitude voltage waves in quadrature at different but slower frequency #2 and applying them to two pairs of main deflector plates 15, 16 respectively, to rotate the beam at a second slower speed, means for applying independent potentials to the two grids, a carrier frequency to the inner grid and a DC potential to the outer grid, signals to be stored being applied to conductive ring 25, an output circuit being connected to conductive ring 24 the beam being split into 2 parts by anode 9 with holes 7, 8 and the parts being centred by plates 10, 11, 10, 12 plates 11, 12 being biased by adjustable potentiometers, the inner and outer grids 20, 21 registering with the inner and outer rings 24, 25 respectively and both grids and rings registering with different parts of strips 22. Crosstalk is minimised by means of screening plates between 13, 15 and 14, 16 e.g. the plate 17 shown. There may be 3000 radial strip electrodes 22 of gold coatings on a "Pyrex" (Registered Trade Mark) plate 19 and of length equal or slightly greater than the distance from the outer periphery of the outer grid to the inner periphery of the inner grid and the outer diameters of gold ring electrodes 24, 25 are equal to the mean diameters of grids 20, 21. Ring electrode 23 collects secondary emission from strips 22 during reading and writing. The incoming signal appears on aerial 26, 27 of continuously rotating directivity, e.g. made up of two mutually perpendicular aerials 26, 27 plus a radio goniometer comprising mutually perpendicular fixed coils 28, 29 and rotating coil 30 driven by electric motor 31 which energizes receiver 40 the output of which is the tube input at outer ring 25, while the output from inner ring 24 is fed via amplifier 41, detector 42, and amplifier 43 to the videogrid of cathode ray display tube 45 which shows the direction of the incoming signal by means of a radial rotating trace and to meter 44 in parallel therewith. Since a carrier frequency is applied by source 49 to inner grid 20, the output is the carrier amplitude modulated by the input signal, and output amplifier 41 is relative to the frequency of 49. The electric motor 31 also drives induction generators 32, 33, the latter generating a frequency (100cps) equal to the speed of rotation of goniometer coil 30 and 32 generating a lower frequency (10 cps) which are fed respectively to phase splitters 37, 34 to generate respective sets of quadrative waveforms which are respectively supplied to sets of deflecting plates 13, 14 ; 15, 16 to cause both beam ports to rotate at different speeds. The outer beam 3a will thus store charges at 100 times (complete revolutions) per second, and the inner beam 3b discharges at 10 times (complete revolutions) per second for reading. Going round the target, the stored signal on the electrodes 22 will show a minimum at the ends of the diameter corresponding to the direction of minimum received signal. Reading destroys the stored information. Display tube 45 may be replaced by or associated with any other device for indicating the direction of the incoming signal. The aerial can be replaced by a rotating frame ordipole rotating the directivity of the aerial will produce a frequency equal to the speed of rotation of the directivity ; this frequency is separated from the received signal in any desired way and used as one deflecting frequency for the tube, the other deflecting frequency being obtained from it by frequency division. If the aerial itself rotates, the driving means for the aerial also energizes the deflection generators ; one of the generators may produce a different frequency from the first by frequency division. The circular stem of display tube 45 is synchronised with the rotating directivity aerial by means of deflecting coils fed by the two quadrature outputs from phase splitter 34. The gun has three anodes 5, 6, 7 and a beam forming electrode 4.