Patent ID: 7501977

Claim:
A Mode S radar which specifies an aircraft by transmitting interrogations to a Mode S transponder installed in an aircraft, by receiving replies to the interrogations, and by then decoding the contents of the received replies, the Mode S radar comprising: acquisition means, which transmits a Mode S only all-call interrogation, and which thereby accomplishes an initial acquisition of an aircraft equipped with a Mode S transponder (a Mode-S-transponder-equipped aircraft); first obtainment means, which transmits UF=4 interrogations as Mode S selective interrogations to the Mode-S-transponder-equipped aircraft with the initial acquisition having been accomplished by the acquisition means, and which thereby obtains DF=4 replies from the Mode-S-transponder-equipped aircraft; second obtainment means, which, until an identicalness judgment is issued, transmits UF=5 interrogations as Mode S selective interrogations with each UF=4 interrogation to the Mode-S-transponder-equipped aircraft, and which thereby obtains Mode A codes as DF=5 replies from the Mode-S-transponder-equipped aircraft; judgment means, which judges whether or not an identicalness exists among predetermined plural Mode A codes obtained by the second obtainment means and issues the identicalness judgment to the second obtainment means; and generation means, which stores, in a memory, data with identicalness having been judged to exist by the judgment means, and which then generates a report obtained by substituting the Mode A code with identicalness having been judged to exist, as a detection report on the aircraft in each of scans following the obtainment.