Automatic correlation circuits

Claim 1

IN A PULSE RADAR SYSTEM EMPLOYING A LONG TIME DELAY IN THE RECEIVER CIRCUIT WHEREIN IT IS REQUIRED THAT AN INTEGRAL NUMBER OF THE PULSE REPETITION PERIODS OF THE TRANSMITTED PULSES BE MAINTAINED EQUAL TO SAID LONG TIME DELAY, A CORRELATION CONTROL CIRCUIT COMPRISING MEANS FOR DERIVING A FIRST SIGNAL CONTAINING A PLURALITY OF STATIONARY TARGET SIGNAL RETURNS OF SAID TRANSMITTED PULSES, FIRST DELAY MEANS FOR DELAYING SAID FIRST SIGNAL BY A PERIOD OF LESS THAN TWICE SAID PULSE WIDTH TO PROVIDE A FIRST DELAYED SIGNAL, MEANS FOR SUBTRACTING SAID FIRST SIGNAL AND SAID FIRST DELAYED SIGNAL TO OBTAIN A DIFFERENCE SIGNAL, SECOND DELAY MEANS FOR DELAYING SAID FIRST SIGNAL BY A PERIOD EQUAL TO SAID LONG TIME DELAY PLUS A PERIOD OF ONE HALF THE TIME DELAY OF SAID FIRST DELAY MEANS TO PROVIDE A SECOND DELAYED SIGNAL, MEANS FOR MULTIPLYING SAID DIFFERENCE SIGNAL BY SAID SECOND DELAYED SIGNAL TO OBTAIN A PRODUCT SIGNAL, MEANS FOR INTEGRATING SAID PRODUCT SIGNAL TO OBTAIN AN ERROR SIGNAL WHOSE SIGN AND MAGNITUDE IS INDICATIVE OF THE DIFFERENCE IN TIME BETWEEN SAID PULSE REPETITION PERIOD AND SAID LONG TIME DELAY, AND MEANS FOR CORRECTING SAID PULSE REPETITION PERIOD IN ACCORDANCE WITH SAID ERROR SIGNAL.