Patent ID: 7570194

Claim:
A system for locating and identifying cooperating mobiles carrying a transponder of a secondary surveillance radar (SSR) apt to emit an SSR signal, the system comprising: a plurality of measuring stations; one or more reference transponders, installed in known positions, for performing time synchronization of the measuring stations with respect to an assigned measuring station used as a temporal reference station, so producing a single temporal reference for the system, on the basis of a difference between a time of arrival of a signal from the transponder to the assigned measurement station and a time of arrival to the station to be synchronized; and a processing subsystem, wherein each measuring station comprises a processing section for processing an SSR signal emitted by a mobile, said SSR signal comprising a preamble including a sequence of pulses, so to obtain a measure of the time of arrival referred to a clock of said station, said processing section being configured to: detect an SSR signal emitted by a mobile by analysing the output of a matched filter to a preamble of said signal; filter said SSR signal by application of a single-pulse matched filter; differentiate the output of the single-pulse matched filter; determine the time of arrival of each pulse by determining the zero-crossing of the differentiated matched filtered signal; reduce error variance of the time of arrival by computing an arithmetic mean of the values relative to the several pulses that constitute the signal, and wherein said processing subsystem collects data related to said measured time of arrival and reconstructs position and identity of the mobiles.