Automatic frequency locking circuit

Claim 1

IN A TEST SET FOR CALIBRATING THE RANGE OF A RADAR SET: (A) MEANS TO RECEIVE FROM THE RADAR SET A RADAR SIGNAL COMPOSED OF A SEQUENCE OF RF RADAR PULSES; (B) MEANS INCLUDING A FIRST OSCILLATOR TO CONVERT SAID RF RADAR PULSES TO AN IF RADAR SIGNAL COMPOSED OF A SEQUENCE OF IF RADAR PULSES; (C) MEANS TO CONVERT SAID IF RADAR PULSES TO A SEQUENCE OF VIDEO PULSES; (D) MEANS TO CONVERT SAID VIDEO PULSES TO A SEQUENCE OF TRIGGER PULSES DELAYED IN TIME RELATIVE TO SAID RF RADAR PULSES; (E) MEANS INCLUDING A SECOND OSCILLATOR RESPONSIVE TO SAID TRIGGER PULSES FOR PRODUCING A SEQUENCE OF IF ECHO PULSES DELAYED WITH RESPECT TO SAID IF RADAR PULSES; AND (F) AN AUTOMATIC FREQUENCY LOCKING CIRCUIT RESPONSIVE TO SAID IF RADAR PULSES AND THE OUTPUT OF SAID SECON OSCILLATOR FOR AUTOMATICALLY TUNING THE LATTER TO THE SAME FREQUENCY AS SAID IF RADAR PULSES WHEN THE FREQUENCY OF SAID SECOND OSCILLATOR IS REMOVED FROM THE FREQUENCY OF THE IF RADAR PULSES BY AN AMOUNT GREATER THAN HALF THE DIFFERENCE BETWEEN THE FREQUENCY OF THE IF RADAR PULSES AND ONE OF THE FIRST SIDEBANDS OF THE IF RADAR SIGNAL,