Quasi coherent two-way ranging apparatus

Claim 1

Apparatus for determining the range between the first station and a second station by measuring the time required for radio frequency signals to be transmitted between the stations without turn-around coherency, the combination comprising: a first pseudonoise generator for generating a plurality of unique coded signals, a stable master clock for driving said first pseudonoise generator, first station start epoch detecting means coupled to said first pseudonoise generator for detecting a predetermined one of said unique coded signals and for generating an epoch marker start signal, a ranging system at said first station coupled to said epoch marker start signal, first station transmitting means coupled to said first pseudonoise generator, second station receiving means adapted to receive the transmitted first station pseudonoise generated signals, second station tracking means coupled to said second station receiving means for locking-on said first station pseudonoise generated signals and for generating second station synchronized clock signals, said second station tracking means comprising a second pseudonoise generator driven by said second station synchronized clock signal and for locking-on said first station pseudonoise generated signals, second station detecting means for detecting the presence of said predetermined one of said unique coded signals and for simultaneously generating a new epoch read signal, a third pseudonoise generator driven by said synchronized clock signals without being synchronized with said second pseudonoise generator, second station transmitting means coupled to said third pseudonoise generator, first station receiving means adapted to receive the second station transmitted signals from said third pseudonoise generator, first station tracking means coupled to said first station receiving means for locking-on said second station pseudonoise generated signals and for generating first station synchronized clock signals, said first station tracking means comprising a fourth pseudonoise generator driven by said first station synchronized clock signals for locking-on said second station pseudonoise generated signals, first station stop epoch detecting means coupled to said fourth pseudonoise generator and said ranging system for detecting a new epoch and for generating a stop signal, new epoch storage means responsive to said new epoch read signal from said second station detecting means for reading and storing a new unique coded signal from said third pseudonoise generator into said new epoch storage means to provide a new epoch signal, said new epoch storage means being coupled to said second station transmitting means for selectively transmitting said new epoch signal to said first station receiving means and said first station stop epoch detecting means, said new epoch signal being transmitted from said second station to said stop epoch detecting means in said first station and being stored and compared with the output signals from said fourth pseudonoise generator until said output signals compare with said stored new epoch to produce a new epoch stop signal, and said ranging system comprising ranging logic being started by said epoch marker start signal and being stopped by said new epoch stop signal, whereby the time duration between said epoch start signal and said new epoch stop signals is indicative of the range between said stations.