Patent GB-1002972-A (GB)
Title: Improvements relating to radar systems for landing aircraft
Inventor: KUHL HANS
IPC: G01S1/02
Filed: 1962-02-20
Abstract: 1,002,972. Radar. J. EITZENBERGER. Feb. 20, 1962, No. 6599/62. Heading H4D. A radar system which is carried by an aircraft and which co-operates with reflector or responder beacons marking the boundaries of a landing runway comprises two antennae systems for scanning the space sector containing the runway beacons, to provide signals from one system representing the azimuth angles and from the other system signals representing the elevation angles of the beacons relative to the aircraft, and an image reproducer operable by said signals to provide an image in perspective of the beacons corresponding to the view thereof which would be obtained by a pilot directly observing the beacons from the aircraft. A first, azimuth antenna system comprises an antenna 2 producing a fan beam having its broad dimension vertical and slowly scanning said beam in azimuth. The second, elevation antenna system comprises an antenna 3 producing a fan beam having its broad dimension horizontal, and rapidly scanning said beam up and down in elevation. Pulses are simultaneously fed to the two antennae from a transmitter 1 and the echoes from passive responders on the replies from active responders, are received by the antennae and fed to the respective azimuth and elevation receivers 6 and 7. The received azimuth pulses are fed to an azimuth measuring circuit 11 and a distance measuring circuit 10, while the received elevation pulses are fed to an elevation measuring circuit 12. The azimuth of a responder producing a pulse, is measured by determining the time between the start of the azimuth scan and the reception of the pulse; whilst the elevation is measured by determining the time between the start of the elevation scan and the reception of the pulse. The distance of the responder is measured by determining the time between the transmission of a pulse and the reception of the echo on reply of the pulse. The received azimuth and elevation pulses are then passed, unchanged to an AND gate coincidence stage, where only those azimuth and elevation pulses occurring at exactly the same time, and thus arising from the same responder, are passed. The passed pulses cause the production of corresponding mark pulses in mark producer 14 which are fed via an amplitude and duration control means 15 to a C.R.T. display 9. The amplitude (brightness) and duration of the responses on the display are controlled by signals from distance measuring circuit 10 in inverse ratio to the distance of the responder. Near responders are thus shown as brighter and larger responses. The scan of the display 9 corresponds to the movement of the point of intersection of the beams from antennae 2 and 3 and may, when the beam scanning is by movement of the antennae, be controlled by signals from potentiometers coupled to the rotating shafts of the antennae, or, when the beam scanning is electronic, be controlled by signals from the azimuth and elevation measuring circuits 11 and 12. The output of distance measuring circuit 10 may be fed to the coincidence stage as a check. In an alternative scanning mode, the azimuth and elevation scans may be at nearly the same speed so that the point of intersection of the two beams moves in a path causing a scan on the display parallel to a diagonal of the display screen.