Noncoherent two way ranging apparatus

Apparatus for determining the range between a first station and a second station by measuring the time required for radio frequency signals to be transmitted between the stations, the combination comprising:

• a first station pseudonoise generator 14 for generating a plurality of unique coded signals,
• a first station reference clock 11 for driving said first station pseudonoise generator,
• first station means for detecting 19 a predetermined one of said unique coded signals and for generating a first station epoch marker signal,
• a first ranging system 21 started by said first station epoch marker signal,
• first station transmitter means 17, 18 coupled to said first station pseudonoise generator for transmitting the output of said first station pseudonoise generator to said second station,
• second station receiver means 46, 47 for receiving said first station transmitted signals,
• second station means for detecting 48 said unique coded signals transmitted from said first station and for generating a delayed first station epoch marker signal,
• a second station pseudonoise generator 25 for generating the same plurality of unique coded signals as said first pseudonoise generator,
• a second station reference clock 23 for driving said second station pseudonoise generator,
• second station means for detecting 31 the predetermined one unique coded signal of said plurality of said unique coded signals and for generating a second station epoch marker signal, a second station ranging system 33 started by said second station epoch marker signal,
• second station transmitter means 28, 29 coupled to said second station pseudonoise generator for transmitting said second station unique coded signals to said first station,
• first station receiver means 34 for receiving said second station unique coded signals,
• first station means for detecting 36 said predetermined one of said unique coded signals transmitted from said second station and for generating a delayed second station epoch marker signal,
• said first station ranging system being stopped by said delayed second station epoch marker signal, and
• said second station ranging system being stopped by said delayed first station epoch marker, whereby the sum of the ranges detected at said first station ranging system and said second station ranging system is equal to the turn-around range between said first station and said second station plus known delays, and the difference of the ranges detected is equal to twice the offset of the reference clocks.