Patent GB-756805-A (GB)
Title: Improvements in or relating to radar systems
Inventor: CUFFLIN MAURICE HAROLD
IPC: G01S7/22
Filed: 1954-07-19
Abstract: 756,805. Radar; cathode-ray tube circuits. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. May 9, 1955 [July 19, 1954], No. 20933/54. Class 40 (7). A radar system having a P.P.I. display is provided with an adjustable marker line on the display so that the bearing and range from one selected object indicated to another can be readily determined. The means for producing the marker comprise a sawtooth generator feeding an adjustable resolver whose X and Y coordinate outputs are added to respective adjustable D.C. voltages and then fed to the two mutually perpendicular deflecting systems of the display tube during at least some inter-traco periods. Adjustment of the D.C. voltages is effective to locate the origin of the marker line produced in coincidence with the first selected indication while adjustment of the resolver moves the line angularly so that it can be orientated to pass through the second indication. Range calibration pips can be provided along the marker line and a number of sets of marker line producing apparatus may be provided which can be made effective during differing, inter-trace periods to provide a like plurality of independent marker lines on the display. In one embodiment the pulse radar trigger pulses are applied at 1 to a waveform generator 2 which provides waveforms a, b, c, and d (Fig. 2) over the output lines indicated by corresponding letters. The sawtooth waveform a is fed to resolver 3 driven in synchronism with the rotation of the aerial 4 to give output scanning voltages fed over switches 5 and 6 and amplifiers 8 and 9 to the deflection system of the display tube 10. With the application of echo signals to brighten up the trace a P.P.I. display, which may include indications T1 and T2, is produced on the tube screen. Square wave-form b is applied to control relay 7 to change over switches 5 and 6 to connect the display tube deflection system to the marker line producing means during inter-trace periods while shorter square wave-form c is applied to gate tube 77 to brighten up the marker trace sufficiently to make it visible. Trigger pulse d coincident with the beginning of pulse c is fed to sawtooth generator 13 to give a signal of wave-form e which is applied to calibrated manually adjustable resolver 14. The X and Y outputs from the resolver are fed respectively to summation amplifiers 17 and 20 fed respectively with D.C. voltages from potentiometers 26 and 27 over D.C. amplifiers 24 and 25. The potentiometer sliders may be jointly controlled by a " joystick " 28 mounted on a central ball joint to control the outputs in accordance with the co-ordinates of the joystick position. The outputs of amplifiers 17 and 20 are fed over switches 5 and 6 to produce the marker line on the tube. Trigger pulses d may also be fed to range marker generator means (including a ringing tuned circuit 72) from which a series of brightening pulses (f, Fig. 2) are applied to the tube over gate valve 77 to produce range spots on the marker line. The origin of the marker line may be made coincident with the indication T1 by means of control 28 and resolver 14 then adjusted so that the line passes through T2. The bearing of the object giving rise to indication 72 from that producing T1 can then be read off from the calibration of the resolver and the distance between them determined by counting the range marker spots appearing between the indications on the bearing line.