Synchronous pulse digital filter

Claim 2

In a ranging system employing repeated range scans each initiated by a search pulse, a detector for us in a receiver for locating a synchronous return pulse occurring among random pulses received during each range scan, said detector comprising: information storage means having a number of memory bits representing a corresponding number of range intervals covering the range being scanned; input means coupled with said storage means for delivering received pulses thereto for storage in memory, and including means for correlating pulse information stored in memory during a given range scan with newly arriving pulses received at the same range intervals during a subsequent range scan, said correlating means causing said storage means to accumulate multiple pulse information at the range at which the synchronous return pulse is occurring and, in each range scan, effecting the destruction of previously stored pulse information at those range intervals where random pulses were received during the previous range scan; and output means responsive to said multiple pulse information for indicating range acquisition when such information corresponds to a predetermined return pulse count sufficient to verify the identity of the synchronous return pulse.

Claim 3

The detector as claimed in claim 1, wherein said multiple pulse information comprises a train of pulses accumulated at the range of the recurring synchronous return pulse, and wherein said correlating means includes means which in successive range scans adds pulses to memory in response to the recurring synchronous return pulse to cause said pulse train to accumulate to said predetermined pulse count.

Claim 4

The detector as claimed in claim 1, wherein said correlating means includes means for subtracting in each range scan one pulse from memory at each range interval where a pulse is not received but where pulse information was stored from a previous range scan or scans, and adding one pulse to memory at each range interval where a pulse is received, whereby only the synchronous return pulse will cause the accumulation of said predetermined pulse count.

Claim 5

The detector as claimed in claim 1, wherein is provided circuit means operable during each range scan to deliver stored pulse information to said input means from said storage means in serial form in synchronism with the successive range intervals of the repeating range scan, and wherein said correlating means is responsive to both the newly arriving pulses and the serial pulse information delivered by said circuit means.

Claim 6

In a ranging system employing repeated range scans each initiated by a search pulse, a detector for use in a receiver for locating a synchronous return pulse occurring among random pulses received during each range scan, said detector comprising: information storage means having a number of memory bits representing a corresponding number of range intervals covering the range being scanned, said memory bits including a first bit representing the first range interval, a final bit representing the last range interval, and intermediate bits rePresenting successive range intervals between said first and final bits; input means coupled with said storage means for exciting the final memory bit in response to pulses received during a range scan; information transfer means coupled with said storage means for transferring the information in said final memory bit to the remaining bits in succession as each range interval of a given range scan occurs in time; circuit means coupled with said first memory bit and said input means and operable during each range scan to recirculate pulse information stored in said storage means during the preceding range scan, said input means including means for correlating recirculating pulse information delivered by said circuit means and newly arriving pulses received in synchronism with the recirculating information to cause said storage means to accumulate multiple pulse information at the range at which the synchronous return pulse is occurring and to effect in each range scan the destruction of previously stored pulse information at those range intervals where random pulses were received during the previous range scan; and output means responsive to said multiple pulse information for indicating range acquisition when such information corresponds to a predetermined return pulse count sufficient to verify the identity of the synchronous return pulse.

Claim 7

In a ranging system employing repeated range scans each initiated by a search pulse, a detector for use in a receiver for locating a synchronous return pulse occurring among random pulses received during each range scan, said detector comprising: information storage means having a number of memory bits representing a corresponding number of range intervals covering the range being scanned, said memory bits including a first bit representing the first range interval, a final bit representing the last range interval, and intermediate bits rePresenting successive range intervals between said first and final bits; input means coupled with said storage means for exciting the final memory bit in response to pulses received during a range scan; information transfer means coupled with said storage means for transferring the information in said final memory bit to the remaining bits in succession as each range interval of a given range scan occurs in time; circuit means coupled with said first memory bit and said input means and operable during each range scan to recirculate pulse information stored in said storage means during the preceding range scan, said input means including means for correlating recirculating pulse information delivered by said circuit means and newly arriving pulses received in synchronism with the recirculating information to cause said storage means to accumulate multiple pulse information at the range at which the synchronous return pulse is occurring and to effect in each range scan the destruction of previously stored pulse information at those range intervals where random pulses were received during the previous range scan; and output means responsive to said multiple pulse information for indicating range acquisition when such information corresponds to a predetermined return pulse count sufficient to verify the identity of the synchronous return pulse.

Claim 8

The detector as claimed in claim 5, wherein said correlating means includes means for subtracting in each range scan one pulse from memory at each range interval where a pulse is not received but where pulse information was stored from a previous range scan or scans, and adding one pulse to memory at each range interval where a pulse is received, whereby only the synchronous return pulse will cause the accumulation of said predetermined pulse count.

Claim 9

The detector as claimed in claim 6, wherein said correlating means includes means for effecting said accumulation of multiple pulse information in said storage means by successive excitation of the final memory bit commencing with the range interval at which the synchronous return pulse is occurring, whereby a pulse train is stored in a series of as many adjacent memory bits as the number of pulses of the pulse train, and wherein said output means indicates range acquisition when said number of pulses of the pulse train equals said predetermined pulse count.

Claim 10

The detector as claimed in claim 7, wherein means is provided coupled with said input means and responsive to pulse information at the time of delivery thereof to said storage means by said input means for blocking any pulses received during a predetermined plurality of range intervals thereafter, whereby to prevent interference with the operation of said correlating means.

Claim 11

The detector as claimed in claim 7, wherein said information transfer means includes a clock for generating clock pulses at a repetition rate corresponding to said range intervals, and wherein said storage means includes a shift register responsive to said clock pulses and provided with said number of memory bits, said transfer means commencing delivery of said clock pulses to said shift register in response to the search pulse initiating each range scan and terminating said delivery after the last range interval of the scan.

Claim 12

The detector as claimed in claim 9, wherein said storage means has a plurality of additional memory bits, and wherein means is provided coupled with said register for inserting an index code into said additional memory bits to designate the limit of the range being scanned, said transfer means terminating said delivery of clock pulses to the register when said index code returns to storage in said additional bits after a recirculation cycle.

Claim 13

The detector as claimed in claim 10, wherein means is provided coupled with said input means and responsive to said recirculating pulse information for blocking any pulses received during a plurality of range intervals before each range interVal or series thereof in which pulse information was stored during the preceding range scan, whereby to prevent received pulses from being stored in a configuration duplicating said index code.

Claim 14

The detector as claimed in claim 9, wherein said transfer means includes means for counting said clock pulses to determine when each scan has been completed, and means responsive to a determination that a scan has proceeded through the last range interval for effecting said termination of delivery of clock pulses to the register.

Claim 15

The detector as claimed in claim 7, wherein said output means includes means which continues to indicate range acquisition only so long as said pulse train in succeeding range scans contains at least a predetermined minimum number of pulses.

Claim 16

The detector as claimed in claim 5, wherein is provided tracking means coupled with said output means and responsive to said indication of range acquisition for generating a track gate during subsequent range scans which occurs in the range interval of the synchronous return pulse, and means responsive to said search pulse and said track gate for measuring the time duration therebetween in each range scan to determine the distance represented by the synchronous return pulse.

Claim 17

The detector as claimed in claim 5, wherein said multiple pulse information comprises a train of pulses accumulated at the range of the recurring synchronous return pulse, and wherein said correlating means includes means which in successive range scans adds pulses to memory in response to the recurring synchronous return pulse to cause said pulse train to accumulate to said predetermined pulse count.

Claim 18

In a ranging system employing repeated range scans each initiated by a search pulse, a method of locating a synchronous return pulse occurring amoung random pulses received during each range scan, said method comprising the steps of: a. establishing a number of range intervals covering the range being scanned; b. during an initial range scan, remembering the range intervals in which pulses are received; c. during the next range scan, destroying from memory those pulses in range intervals in which the pulses fail to recur, and remembering the range intervals in which newly arriving pulses occur; d. during succeeding range scans, continuing to remember the range intervals in which newly arriving pulses occur to thereby accumulate a pulse count of greater than unity representing the range interval in which the synchronous return pulse is occurring, and reducing the pulse count by one each time the synchronous pulse fails to recur; and e. indicating range acquisition when said pulse count reaches a predetermined number sufficient to verify the identity of the synchronous return pulse.

Claim 19

In a ranging system employing repeated range scans each initiated by a search pulse, a method of locating a synchronous return pulse occurring amoung random pulses received during each range scan, said method comprising the steps of: a. establishing a number of range intervals covering the range being scanned; b. during an initial range scan, remembering the range intervals in which pulses are received; c. during the next range scan, destroying from memory those pulses in range intervals in which the pulses fail to recur, and remembering the range intervals in which newly arriving pulses occur; d. during succeeding range scans, continuing to remember the range intervals in which newly arriving pulses occur to thereby accumulate a pulse count of greater than unity representing the range interval in which the synchronous return pulse is occurring, and reducing the pulse count by one each time the synchronous pulse fails to recur; and e. indicating range acquisition when said pulse count reaches a predetermined number sufficient to verify the identity of the synchronous return pulse.

Claim 20

The method as claimed in claim 15, wherein said step (d) includes subtracting from memory one pulse at each range interval in which a new pulse fails to arrive but where pulse information has been remembered from a previous range scan or scans, and adding to memory one pulse at each range interval in which a new pulse arrives, whereby only the synchronous return pulse will result in the accumulation of said predetermined pulse count.

Claim 21

The method as claimed in claim 15, wherein said step (d) includes adding pulses to memory in successive range scans in response to the recurring synchronous return pulse to cause the accumulation of a train of pulses at the range of the synchronous return pulse, and wherein said range acquisition in said step (e) is indicated when the number of pulses in said train equals said predetermined pulse count.

Claim 22

In a ranging system employing repeated range scans each initiated by a search pulse, a detector for use in a receiver for locating a synchronous return pulse occurring among random pulses received during each range scan, said detector comprising: information storage means having a number of memory bits representing a corresponding number of range intervals covering the range being scanned; input means coupled with said storage means for delivering received pulses thereto for storage in memory, and including means for correlating pulse information stored in memory during each range scan with newly arriving pulses received at the same range intervals during the next range scan, said correlating means in each range scan causing said storage means to store correlated pulse information at the range at which the synchronous return pulse is occurring; and output means responsive to said correlated pulse information for indicating range acquisition when such information corresponds to a sufficient number of recurrences of said synchronous return pulse to verify its identity.

Claim 23

In a ranging system employing repeated range scans each initiated by a search pulse, a detector for use in a receiver for locating a synchronous return pulse occurring among random pulses received during each range scan, said detector comprising: information storage means having a number of memory bits representing a corresponding number of range intervals covering the range being scanned; input means coupled with said storage means for delivering received pulses thereto for storage in memory, and including means for correlating pulse information stored in memory during each range scan with newly arriving pulses received at the same range intervals during the next range scan, said correlating means in each range scan causing said storage means to store correlated pulse information at the range at which the synchronous return pulse is occurring; and output means responsive to said correlated pulse information for indicating range acquisition when such information corresponds to a sufficient number of recurrences of said synchronous return pulse to verify its identity.