Patent GB-630552-A (GB)
Title: Improvements in or relating to cathode ray oscillograph apparatus
IPC: G01S7/06
Filed: 1945-07-27
Abstract: 630,552. Radiolocation. BAKER, W. A., SHARPE, C., HOPKINSON, K., BRADFIELD, G., and TUTCHINGS, A. July 27, 1945, No. 19336. [Class 40 (vii)] In a cathode-ray tube display arrangement for use in a pulse radar or similar system, successive linear time-base traces, upon which echo signals are displayed by intensely-modulation of the cathode-ray beam, are displaced from one another in a direction perpendicular to the time-base scanning direction at a predetermined rate, and time-marking signals are caused to appear upon selected ones of the successive time-base traces. The display consequently appears as shown in Fig. 1, wherein successive horizontal scans are displaced vertically from one another. The dots 11 and 12 are both range-marking and time-marking signals and the solid lines are due to echoes received from moving objects. Alternatively, the marking signals may be made to appear as spaces in a generally illuminated display. The display only presents signals from a selectable band of ranges; as shown, only echoes from objects between 60 and 120 miles distant are displayed. The display normally takes 40 seconds to complete, but, if desired, it may be extended for a further 20 seconds (from y to z). A corresponding film-record, as shown in Fig. 2, is also produced by photographing the screen of a cathode-ray tube. Detailed operation, Fig. 3. Pulses coinciding with the exploring pulse are applied to amplifier 17 and then to ringing,circuit 18 which delivers a succession of trains of oscillations at 9.3 kc/s. These are squared at 20 and converted in 21 to 2 micro-second pulses. The output pulses from 17 are also applied to a relaxation oscillator 19 which delivers pulse signals having adjustable trailing edges. Pulses corresponding to these trailing edges are generated in 22 and applied together with the pulses from 21 to the coincidence circuit 23. The pulses delivered from 21 correspond to successive ten-mile intervals of range, and consequently the output from 23 comprises a succession of pulse signals whose timing corresponds to a range equal to a selectable integral multiple of 10 miles. From these signals, multi-vibrator 24 generates a train of square waves which are applied to time-base generator 28 which, together with paraphase amplifier 29 provides sawtooth scanning waveforms which are applied to cathode-ray tubes 30 and 31. The scanning waveforms commence at instants corresponding to the timings of the selected pulses, and thus a chosen band of ranges is displayed. The output pulses from 21 are also applied via switch a1 and bufferstage 27 and via divider-stage 25 which selects every fifth pulse applied thereto, switch b1 and buffer-stage 26 to mixer-circuit 32. Switch a1 which is operated by a relay controlled by a master clock, is closed momentarily once every minute to allow ten-mile marking pulses to be passed to mixer 32. Switch b1 is similarly closed once every six seconds to allow fifty-mile marking pulses to be passed to 32. The marking pulses are mixed in 32 with negativegoing square wave which is used to switch the beam of the cathode-ray tubes on during the scanning intervals. The signals passed by unit 26 consequently produce the dots 11, Figs. 1 and 2, and the signals passed by unit 27 produce the dots 12. The visual display is produced on cathode-ray tube 30, to the verticaldeflecting plates of which the output of the Miller circuit 34 is applied. The circuit 34 is triggered by one or the other of the switches t1 and t2 which are arranged to be operated by motor-driven cams G1 and G2 once every 40 seconds. By means of the change-over switch CS either t1 or t2 may be made the operative switch, and, by changing from one to the other as the time base 34 approaches the end of its scan, the display may be continued for a further 20 seconds. The presentation on cathode-ray tube 31 comprises a horizontal trace which is focused on to a photographic film passing the cathode-ray tube at a uniform rate to provide the record shown in Fig. 2. The echo signals are applied through receiver circuits 36, 37, 38 to the grids of the cathoderay tubes 30 and 31. A switch c1 in the lead to the grid of 31 is operated once every halfhour to produce a gap in the traces produced on the film. Simultaneously, the switches a1 and b1 are closed for several seconds, thus producing a row of marker signals in the form of dashes as shown at 14 in Fig. 2.