Patent GB-712710-A (GB)
Title: Improvements in or relating to radar system
IPC: G01S7/20
Filed: 1952-01-31
Abstract: 712,710. Pulse radar; pulse generating circuits. GILFILLAN BROS., Inc. Jan. 31, 1952 [Feb. 21, 1951], No. 2605/52. Classes 40 (6) and 40 (7) In a pulse radar system, employed particularly for the ground-controlled approach of aircrat, wherein two displays, one showing elevation and range and the other showing azimuth and range, are presented on a single cathode-ray tube as shown in Fig. 2, means are provided for blanking portions of the cathode-ray beam sweeps in the two displays, the extent of the blanking being made dependent upon the elevation and azimuth respectively of the radar beam. Thus re'atively unimportant portions of the displays may be rendered invisible so that the two displays may be more conveniently positioned on the screen of the cathode-ray tube. The radar system comprises two alternately energized aerial systems, one scanning in e!evation and the other in azimuth. Relays are operated in synchronism with the aerial switching to switch the origins of the displays between the points O1 and 02. Potentials are derived corresponding to the settings of the aerials in azimuth and elevation and these are applied alternately in synchronism with the aerial switching to a flip-flop circuit which is triggered by synchronizing pulses which correspond to the pulses radiated by the radar system and returns to its stable state after a time which depends upon the magnitude of the aerial setting voltage applied thereto. The trailing edges of the output square waves of the flip-flop circuit are applied to a further flip-flop circuit generating blanking pulses which are applied to the cathoderay tube. By suitably adjusting the constants of the circuits used, the time-base sweeps may be limited as indicated by the lines EF and HJ in Fig. 2. Means is further provided for preventing the application of the synchronizing pulses to the first flip-flop during transmission from the elevation aerial, when this aerial is set horizontal or inclined upwardly so that a limiting line FG is also produced on the display. In the system described, two cathode ray tubes are employed and present respectively 3-mile and 10-mile displays. The circuits employed for the two cathode-ray tubes are generally similar; however the circuit of the 10-mile displays comprises means for completely preventing the presentation of the elevation display while simultaneously the first flip-flop is rendered inoperative so that no blanking of the azimuth display takes place. The cathode-ray tube displays also include vertical range marks R1, R2, and also so-called V-follower lines U1, VI, U2, V2. Rotatable transparent sheets 62, 63 centred about the desired point of touch down on the two displays and bearing linear markings. are also provided. Presentation of range markers.-Each cathoderay tube comprises a pair of perpendicular deflecting coils which, however, are so arranged that, in the absence of any deflecting current passing through the coil controlled by the aerial settings, current flowing in the other coils produces deflections in a direction parallel to O,K or O 2 E. Consequently in order to obtain vertical range markers R1, R2, the currents applied to the range scanning coils are modified in accordance with the angular settings of the aerials. Beam-centring circuit, Fig. 7.-A circuit as shown in Fig. 7 is associated with each deflecting coil 22B of the cathode-ray tubes. V1116 is the output valve of the corresponding deflection control circuit while valve V1117 which passes different currents according as to whether relay K1102 is actuated or not, permits separate adjustment of the origins of the two displays by adjustment of the tappings upon the potentiometers R1158 and R1159. Pulse generating circuits.-Fig. 8c shows the further flip-flop circuit generating the blanking pulses applied to the cathode-ray tube and triggered by the trailing edges of the square wave output of the first-mentioned flip-flop. The flipflop comprises valves 237 and 262. The crossconnection between the anode of valve 237 and a control electrode of valve 262 being by way of a further valve 269. Specification 676,743 is referred to.