Doppler sonar apparatus

Claim 1

IN A DOPPLER SENSING ECHO RANGING SYSTEM OF THE TYPE INCLUDING A MATCHING SET OF FIRST AND SECOND SIGNAL SELECTIVE UNITS, SAID FIRST UNIT FOR ENCODING A SIGNAL FOR TRANSMISSION TO A TARGET AND SAID SECOND UNIT FOR DETECTION OF THE ENCODED SIGNAL IN THE ECHO SIGNAL RETURNING FROM THE TARGET, SAID FIRST AND SECOND SIGNAL SELECTIVE UNITS EACH COMPRISING A PREDETERMINED SERIES OF PARALLEL CONNECTED BAND PASS FILTERS AND A FREQUENCY COMPONENT PHASE SELECTIVE MEANS ASSOCIATED WITH SAID SERIES OF FILTERS FOR PASSING ONLY THE OUTPUT FREQUENCY COMPONENTS OF THE INDIVIDUAL FILTERS WHICH ARE IN EITHER ONE OF THE OTHER OF OPPOSITE SIGNAL PHASE CONDITIONS IN ACCORDANCE WITH A PREDETERMINED RANDOM BINARY NUMBER CODE, THE IMPROVEMENTS, IN COMBINATION, COMPRISING: (A) THE INDIVIDUAL BAND PASS FILTERS OF THE SERIES OF FILTERS OF THE FIRST SIGNAL SELECTIVE UNIT HAVING CENTER FREQUENCIES THAT INCREASE IN ACCORDANCE WITH A FIRST PREDETERMINED PORTION OF A PREDETERMINED GEOMETRIC PROGRESSION, AND HAVING BANDWIDTHS THAT INCREASE IN PROPORTION TO THEIR RESPECTIVE CENTER FREQUENCIES, AND (B) SAID INDIVIDUAL BAND PASS FILTERS OF THE SECOND SIGNAL SELECTIVE UNIT HAVING CENTER FREQUENCIES THAT INCREASE IN ACCORDANCE WITH A SECOND AND DIFFERENT PREDETERMINED PORTION OF SAID PREDETERMINED GEOMETRIC PROGRESSION, AND HAVING BANDWIDTHS THAT INCREASE IN DIRECT PROPORTION TO THEIR RESPECTIVE CENTER FREQUENCIES, (C) SAID FIRST AND SECOND PREDETERMINED PORTIONS OF THE PREDETERMINED GEOMETRIC PROGRESSION BEING MATCHED TO ALLOW ONLY A SIGNAL ENCODED BYTHE FIRST SIGNAL SELECTIVE UNIT AND SHIFTED BY A PREDETERMINED DOPPLER CONDITION TO PASS THROUGH THE SECOND SIGNALS SELECTIVE UNIT.