Passive ranging technique

Claim 1

In a passive ranging system for use on a slow moving platform incorporating means for determining range to an emitting source which comprise at least two physically separated antenna means for receiving signals from a radiating source; receiver means operatively connected to said at least two antenna means for producing output video signals and intermediate frequency signals; time of arrival computing means operatively connected to said receiver means and receiving said video signals and measuring the difference in time of arrival between the signals received at said at least two antenna means and producing a signal corresponding to bearing to the source; phase rate computer means operatively coupled to the output of said receiver means for receiving the intermediate frequency signals therefrom and producing sum signal and a quadrature sum signal; means operatively connected to said phase rate computer means for computing a phase rate beat frequency; modifying means operatively receiving the bearing signal and modifying said bearing signal for various measured parameters; and combining means operatively connected to said modifying means and said phase rate computing means combining said modified bearing signal and said phase rate beat frequency and outputting a signal representative of range to the emitting source; the improvement comprising a multiplicity of sets of receiving antennas at spaced intervals along the slow moving platform so that an induced velocity is added to the received signals.