GB604273A - Improvements in radiolocation apparatus - Google Patents

Abstract

604,273. Electric synchronous movements. GENERAL ELECTRIC CO., Ltd., and HAWES, D. O. Nov. 19, 1943, No. 19412. [Class 40 (iii)] [Also in Groups XXXVIII and XL (c)] In a pulse-radiolocation system employing continuous scanning, a plan-position indication is produced ori a cathode-ray tube at a remote point by transmission over a radio link of echo signals and synchronising signals indicative of both the scanning speed and the instant of transmission of pulses. The radiolocation system, Fig. 1, comprises a scanner 1 continuously rotated by a motor 2 and fed with pulses from a transmitter 14 through a switch device 15 of known type, comprising for instance, a gasdischarge tube. The pulsing of the transmitter is controlled by a rotary switch 4 comprising a drum with alternate conducting and insulating segments bridging brushes 5, 6 to produce the waveform 9 which is differentiated at 8 to produce the wave 10. The unit 11 produces pulses 13 to control the transmitter and also synchronising signals 12. Transmitted pulses 13 and echo pulses 18 obtained from the receiver 16, may be displayed on a monitor indicator 64 and are fed together with the synchronising signals to amplitude modulate a transmitter 17, as indicated in Fig. 2. A characteristic pulse 26 of opposite polarity to the synchronising pulses is generated by cam 19 and contacts 21 when the scanner faces a determined position, e.g. north, and is also fed to modulate the transmitter 17. Contact 21 is mounted on a member 28 which is rotatably mounted on the shaft 3 driving the scanner and is coupled by gearing to a gyro compass 32, so that the pulse 26 may be generated at a definite bearing irrespective of movement of the whole equipment. The output of the receiver 38, Fig. 3, which receives the signals from transmitter 17 at the remote point, is fed to the grid of a cathode-ray tube 36 to produce the normal plan-position indication. The synchronising signals are separated out at 38 and produce in unit 41 a saw-tooth current wave which is fed to the deflector coils 46 to produce the time-base deflection. The synchronising pulses are also fed to unit 40 to produce a series of calibration pulses which are fed to the C.R. tube cathode. Unit 42 amplifies the synchronising pulses and feeds them through brushes and slip rings to the stator 56 of a synchronous motor, the rotor 57 of which drives the deflecting coils in step with the rotation of the scanner. The " North " pulse 26 will be visible as a large bright patch on the cathode-ray tube screen and by rotating the stator 56 this indication may be brought to any desired position on the screen. The synchronous motor for driving the deflecting coils may be replaced by a uni-selector mechanism which causes the gearing and coils to be rotated through a predetermined angle for every synchronising pulse. In order to enable the position of the radiolocation equipment relative to the remote indicating station to' be determined, a responder may be installed at that station, and transmit a coded signal on receipt of the pulse from the radio-location transmitter. This signal, received by the receiver 16, is re-transmitted back over the radio link to the indicating station where it appears on the plan position indicator. It is stated that the invention is also applicable to systems in which the scanning does not comprise continuous rotation but to and fro motion over a desired arc.