Radio location ranging system

Claim 1

A RADIO POSITION FINDING SYSTEM COMPRISING A MOBILE UNIT AND TWO FIXED, SPACED APART TRANSPONDER STATIONS, SAID MOBILE UNIT COMPRISING MEANS FOR SIMULTANEOUSLY RADIATING FIRST AND SECOND PURE, UNMODULATED SIGNALS OF PREDETERMINED FREQUENCIES IN DIFFERENT FREQUENCY CHANNELS DURING SPACED APART INTERVALS, RECEIVING AND INDICATING EQUIPMENT EFFECTIVE DURING PERIODS BETWEEN THE SPACED APART INTERVALS, MEANS FOR GENERATING A REFERENCE SIGNAL HAVING ITS PHASE LOCKED TO SAID FIRST SIGNAL, AND TIMING MEANS FOR RENDERING THE RADIATING MEANS AND SAID EQUIPMENT ALTERNATELY EFFECTIVE; EACH OF SAID TRANSPONDER STATIONS INCLUDING MEANS FOR SIMULTANEOUSLY RADIATING DURING SAID PERIODS FIRST AND SECOND PURE, UNMODULATED WAVES HAVING FREQUENCIES RESPECTIVELY EQUAL TO THE FREQUENCIES OF SAID FIRST AND SECOND SIGNALS, MEANS FOR RECEIVING SAID FIRST AND SECOND SIGNALS DURING SAID INTERVALS, AND PHASE ADJUSTING MEANS FOR RESPECTIVELY LOCKING THE PHASES OF THE FIRST AND SECOND WAVES TO THE PHASES OF THE RECEIVED FIRST AND SECOND SIGNALS; MEANS RESPONSIVE TO AT LEAST ONE OF SAID FIRST AND SECOND SIGNALS FOR RENDERING THE RADIATING MEANS OF THE TWO TRANSPONDER STATIONS ALTERNATELY EFFECTIVE DURING SAID PERIODS; THE RECEIVING THE WAVES RADIATED FROM EACH OF THE MEANS FOR RECEIVING THE WAVES RADIATED FROM EACH OF THE TRANSPONDER STATIONS AND FOR COMPARING THE PHASE OF THE FIRST WAVE RECEIVED FROM A FIRST OF THE TRANSPONDER STATIONS WITH SAID REFERENCE SIGNAL TO PROVIDE A FIRST FINE POSITION INDICATION REPRESENTING THE POSITION OF THE MOBILE UNIT RELATIVE TO SAID FIRST STATION, SAID EQUIPMENT INCLUDING MEANS JOINTLY RESPONSIVE TO THE TWO WAVES RECEIVED FROM SAID FIRST TRANSPONDER STATION FOR PROVIDING A FIRST COARSE POSITION INDICATION REPRESENTING THE LOCATION OF THE MOBILE UNIT RELATIVE TO SAID FIRST STATION, SAID EQUIPMENT INCLUDING MEANS FOR COMPARING THE PHASE OF SAID REFERENCE SIGNAL WITH THE FIRST WAVE RECEIVED FROM THE SECOND OF SAID TRANSPONDER STATIONS TO PROVIDE A SECOND FINE POSITION INDICATION REPRESENTING THE LOCATION OF THE MOBILE UNIT RELATIVE TO SAID SECOND STATION, AND MEANS JOINTLY RESPONSIVE TO THE TWO WAVES RECEIVED FROM THE SECOND STATION FOR PROVIDING A SECOND COARSE POSITION INDICATION REPRESENTING THE POSITION OF THE MOBILE UNIT RELATIVE TO SAID SECOND STATION.