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SECONDARY RADAR SYSTEM

  • US 3,772,688 A
  • Filed: 07/12/1971
  • Issued: 11/13/1973
  • Est. Priority Date: 07/17/1970
  • Status: Expired due to Term
First Claim
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1. A secondary radar system comprising at least one interrogator and a plurality of responder beacons cooperating therewith, means for coupling said interrogator in time and angle to a primary radar system by means of a common directive scanning antenna, said responder beacons being either stationary mounted or mounted in mobile objects, said system further characterized in that for obtaining the desired data, such as bearing and distance, of a number of selected objects together with an object identification during one searching sweep, said interrogator includes means adapted for calling the selected objects one by one in a predetermined sequence by transmitting an address different for each responder beacon (2) by means of a transmission code, said transmission code being reconstructible after channel distortion and suitable for asynchronous transmission, and means in each said responder beacon responsive to having been called with its address and having recognized same for emitting a short pulse (22) at a carrier wave frequency other than the carrier wave frequency of the radar pulse (20) of the primary radar system only at the moment said beacon is scanned by said primary radar pulse.

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