Patent GB-600586-A (GB)
Title: Improvements in or relating to pulse radar systems
IPC: G01S7/20
Filed: 1945-10-23
Abstract: 600,586. Radiolocation. KEMPTON. A. E., and CHICK, D. R. Oct. 23, 1945, No. 27972. [Class 40 (vii)] In a pulse radar system the receiver aerial has two flat polar lobes lying in planes differently inclined to the vertical and rendered effective alternately or together to scan in azimuth so that a projectile gives rise to two traces on a cathode-ray tube range-bearing display, the traces intersecting at points corresponding to the position at-which the projectile is released from and reaches ground level. If a radar system having a rotating antenna with a flat polar lobe inclined to the vertical is used to determine the position of an object, an error will be introduced dependent on the height of the object and the inclination of the lobe. Differently inclined lobes will introduce different errors, but the true bearing of objects at ground level will be given by all and two suitable traces extrapolated if necessary can be used to determine the releasing and landing points of a projectile. It is preferred to use a system with one vertical lobe to provide a position indication which is correct at any height and one lobe at an angle of about 45 degrees to the vertical. A pulse-modulated transmitter 1 feeds through a T.R. box 14 to a rotating aerial system 2 through a rotary joint 15 and a switch 16 switching from one fork wave-guide fed reflector A to another B, backing it ; each reflector scans alternately in azimuth over the same 150 degrees sector; for intervening 30 degrees sectors the transmitter is switched out of action by cam-operated switch 19. Received echo signals are fed by receiver 3 as D.C. pulses to line 7 and after amplification used to intensity modulate radial P.P.I. tube 8 and display tubes 9 and 10. Deflection coils 22 of the tube 8 are rotated in synchronism with the rotation of the aerial system and fed with scanning current from generator 23 triggered by a pulse coincident with the transmitted pulse from unit 18. Reversing switch 21 controlled by switch 20 operated by a cam on the rotating aerial is used to superimpose the indications of the two aerials on the same sector of the tube. Tube 9 presents range vertically and a selected 25 degrees of the bearing scale along the horizontal axis. The range time base generator 28 is synchronized from unit 18 by amplifier 29 and the bearing scan is derived from a magslip generator 32 driven at twice the aerial speed and feeding, through adjustable selector 33, a phase-sensitive rectifier 34 whose output, at twice the rotation frequency, is amplified and clipped to give the substantially linear scan by amplifier 35; the range scan is central on the tube at the bearing indicated by selector 33. Tube 10 gives a vernier range indication over an adjustable 2000 yard sweep with the same horizontal bearing scale as tube 9. The saw-tooth output of generator 28 is fed to a strobe pulse generator 36 which generates a pulse at a time dependent on the setting of range potentiometer 37 adjusted by hand wheel C. Ganged to potentiometer 37 is a phasing goniometer 39 adjusting the phase of the output of ringing oscillator 38 triggered from amplifier 29. Calibration " pips " are derived from the output of goniometer 39 in circuit 40 and applied to gate 41 gated by the output of generator 36. One " pip is passed and triggers the fast time base generator 42 of vernier tube 10. The calibration. " pips " from circuit 40 are also passed through a second gate 44 controlled by the fast time base so that brightening range marker pulses are superimposed on the echo pulse signal inputs to the oscillographs corresponding to the range at the centre of vernier tube 10. These range marker pulses may also be applied to the horizontal deflecting plates of tube 9 to draw the range marker line sideways to project out of the picture so that it can be more readily seen. Brightening pulses are passed to the grids of tubes 9 and 10 during the scanning period of generators 28 and 42 respectively and the brightening pulses of the latter are also fed to gate 48 controlled by the output of bearing scan amplifiers 35, a brightening pulse is passed only when the amplifier output is zero, i.e. in the centre of the bearing scales of tubes 9 and 10, and the gate pulse is applied to brighten a whole range trace on all the displays and forms a bearing marker. If preferred, the switching may be arranged for a full 360 degrees scan to be presented on the P.P.I. and the aerials may be arranged side by side instead of back to back. In the side by side arrangement, switches 20 and 21 are not required and electronic high-speed switching may be used at 16. In a further side by side system, switching is dispensed with, a separate transmitting aerial being used together with separate and simultaneously operating receiver channels. Specification 592,835 is referred to.