Multi-target tracker

In a radar tracking system of the transponder type wherein reply signals from one or more remote stations are respectively responsive to interrogation signals having a predetermined repetition rate during a selected period, said period being defined by a predetermined number of said interrogation signals, said system including correlator means including means for generating said interrogation signals, and for correlating replies thereto to identify remote stations and to provide, only during a preselected period prior to said selected period, a hand-over signal representing each of such remote stations,

• a tracker for tracking said reply signals comprising:
• track gate means normally disabled responsive when enabled to said reply signals from remote vehicles respondng to said interrogation signals to generate a digital reply signal representing said remote vehicle;
• sequential storage means, having a plurality of storage stages, responsive to said hand-over signals to store in one of said storage stages a signal representing each of said remote vehicles in the sequence received and corresponding to the relative range to each of said remote vehicles as manifested by the time of receipt of said hand-over signals, and to advance in a clocked sequence indicative of range following each interrogation signal each said stored signal from one stage to another through a given maximum number of stages representing a predetermined maximum range;
• means responsive to said stored signals to generate a track gate enable signal to enable said track gate means at a time substantially coincident with the time of expected reply for each of said remote vehicle reply signals;
• and
• servo means further responsive to said stored signals and to said reply signals to generate control signals to servo sequential movement of said stored signals in said storage means such that the relative storage stage of said stored signal is changed to reduce errors of coincidence in the expected reply signal and said track gate enable signal;
• said sequential storage means being a shift register clocked at a predetermined rate and having a plurality of stages, including an input and output stage, each stage in sequence corresponding to an increment of range, whereby a plurality of digital reply signals are stored simultaneously in a sequence and location corresponding to the range of each of said remote vehicles, and said track gate enable signal is generated at said output stage of said shift register and coupled to said track gate means.