Airport surveillance system

Claim 1

A radar system for airport surface surveillance for identifying the positions on said surface of vehicles including aircraft equipped with SSR transponders responsive to a predetermined P1 and P3 interrogation pulse format providing predetermined P1 to P2 time spacing, and to a P2 pulsed pattern comprising: first means including a plurality of self-timed, mutually asychronous pulsing interrogators providing generally lobe-shaped horizontal radiation patterns, said interrogators distributed along the sides of a pathway in a substantially symmetrical alternating pattern whereby each interrogator is located on a side of said pathway opposite that of the preceding and the next succeeding interrogator along the length of said pathway; second means within each of said interrogators for radiating signals corresponding to said P1 and P3 pulses in a generally lobe-shaped pattern within a corresponding sector across said pathway, and signals corresponding to said P2 pulses in a pattern having lower amplitude within said sector than the amplitude of said lobe-shaped pattern but higher amplitude than said lobe-shaped pattern outside said sector; third means comprising at least two auxiliary equipments spaced from said pathway for receiving the SSR transponder reply signals emitted by said SSR transponders, said auxiliary equipments each being adapted to determine at least one of the discrete parameters consisting of angle of arrival of said SSR reply signals and time of arrival of said SSR reply signals; and fourth means responsive to at least one of said discrete parameters determined by said third means for identifying the instantaneous position of said SSR transponder along said airport surface.