F.m. radar system

Claim 1

MEANS FOR DETERMINING THE DISTANCE OF AN OBJECT FROM A STATION COMPRISING AT THE STATION MEANS FOR TRANSMITTING TO THE OBJECT WAVES OF CONTROLLABLE FREQUENCY AND MEANS FOR RECEIVING SAID WAVES AFTER REFLECTION FROM THE OBJECT, A FIRST MIXER THE INPUT OF WHICH IS SUPPLIED SIMULTANEOUSLY WITH THE TRANSMITTED WAVES AND WITH PREVIOUSLY TRANSMITTED WAVES REFLECTED FROM THE OBJECT, SAID FIRST MIXER PROVIDING AN OUTPUT ONLY OF WAVES HAVING A PRESCRIBED DIFFERENCE IN FREQUENCY BETWSEEN THE WAVES SUPPLIED TO ITS INPUT, AN OSCILLATOR GENERATING WAVES OF A FIXED FREQUENCY DIFFERING BY A SELECTED VALUE FROM THE PRESCRIBED DIFFERENCE, A SECOND MIXER SUPPLIED JOINTLY BY THE OUTPUTS OF THE FIRST MIXER AND OF THE OSCILLATOR AND PROVIDING AN OUTPUT ONLY OF WAVES OF A SECOND PRESCRIBED FREQUENCY DIFFERENCE BETWEEN THOSE OF THE INPUT SUPPLIED TO THE SECOND MIXER, A THIRD MIXER SUPPLIED JOINTLY BY THE OUTPUTS OF THE SECOND MIXER AND OF THE OSCILLATOR AND PROVIDING AN OUTPUT ONLY OF WAVES OF A THIRD PRESCRIBED FREQUENCY DIFFERENCE BETWEEN THOSE OF THE INPUT SUPPLIED TO THE THIRD MIXER, MEANS FOR INDICATING THE EXISTENCE OF AN OUTPUT FROM THE THIRD MIXER, AND MEANS FOR CYCLICALLY VARYING THE FREQUENCY OF THE TRANSMITTED WAVES THROUGH A DESIRED RANGE AT A VARIABLE REPETITION RATE AND MEANS MANUALLY CONTROLLABLE AND INDEPENDENT OF THE RECEIVING MEANS FOR ADJUSTING THE REPETITION RATE TO BRING ABOUT OPERATION OF THE INDICATING MEANS AT A DESIRED STATION-TO-OBJECT DISTANCE, SAID RATE ADJUSTING MEANS BEING PROVIDED WITH A DIAL GRADUATED IN DISTANCE UNITS.