Apparatus for deriving synchronizing pulses from pulses in a single channel pcm communications system

Claim 2

Apparatus for correlating a cyclic square-wave input signal with a replica of said input signal comprising timing means for producing synchronized periodic sample commands and clock pulses, converting means responsive to said sample commands for obtaining an arbitrary number of successive samples per cycle of said input signal and converting each sample to digital form, said digital form consisting of binary signals having two voltage levels representing binary values of plus one and minus one for the two levels of said input square-wave signal, means for generating said replica, said replica having two voltage levels corresponding to binary values of said input signal samples, said two voltage levels of said replica representing plus and minus signs corresponding to signs of said binary values of plus one and minus one of said input signal samples when converted to digital form, and means responsive to said clock pulses for accumulating in digital form a sequence of binary values of said input signal samples produced by said converting means over a number of cycles of said input signal to form a correlation value by arithmetically adding or subtracting the binary value of a given sample to the accumulation of binary values of previous samples under control of said replica according to whether said replica is at the time representing a plus or a minus sign, arithmetically adding when representing a plus sign and arithmetically subtracting when representing a negative sign, whereby after said number of cycles have been sampled, and the binary values thereof have been thus accumulated, said correlation value is proportional to the degree said replica is in phase with said input signal.

Claim 3

Apparatus for correlating a cyclic square-wave input signal with a plurality of phase-displaced versions of a replica of said input signal comprising timing means for producing synchronized periodic sample commands and clock pulses, converting means responsive to said sample commands for converting a number of successive samples per cycle of said input signal to digital form, said digital form consisting of binary signals having two voltage levels representing binary values of plus one and minus one for the two levels of said input square-wave signals, means for generating a plurality of phase displaced versions of said replica, each phase displaced version having two voltage levels corresponding to voltage levels of said input signal, said two voltage levels of each phase displaced version presenting plus and minus signs corresponding to signs of said binary values of plus one and minus one of said input signal samples converted to digital form, and means responsive to said clock pulses for accumulating in digital form a sequence of binary values of said input signal samples produced by said converting means over a number of cycles of said input signal to form a separate correlation value for each phase-displaced version of said replica by arithmetically adding or subtracting the binary value of a given sample to the accumulation of binary values of previous samples under control of separate phase displaced versions for each separate correlation value according to whether each separate phase displaced version is at the time representing a plus or a minus sign, by arithmetically adding when representing a plus sign and arithmetically subtract when representing a negative sign, whereby after said number of cycles have been sampled, and the binary values thereof have been thus accumulated, each correlation value is proportional to the degree that each of the separate phase displaced versions of said replica is in phase with said input signal.

Claim 4

Apparatus for correlating a cyclic square-wave input signal with a plurality of phase-displaced versions of a replica of said input signal comprising timing means for producing synchronized periodic sample commands and clock pulses, converting means responsive to said sample commands for converting a number of successive samples per cycle of said input signal to digital form, said digital form consisting of binary signals having two voltage levels representing binary values of plus one and minus one for the two levels of said input square-wave signals, means for generating a plurality of phase displaced versions of said replica, each phase displaced version having two voltage levels corresponding to voltage levels of said input signal, said two voltage levels of each phase displaced version presenting plus and minus signs corresponding to signs of said binary values of plus one and minus one of said input signal samples converted to digital form, and means responsive to said clock pulses for accumulating in digital form a sequence of binary values of said input signal samples produced by said converting means over a number of cycles of said input signal to form a separate correlation value for each phase-displaced version of said replica by arithmetically adding or subtracting the binary value of a given sample to the accumulation of binary values of previous samples under control of separate phase displaced versions for each separate correlation value according to whether each separate phase displaced version is at the time representing a plus or a minus sign, by arithmetically adding when representing a plus sign and arithmetically subtract when representing a negative sign, whereby after said number of cycles have been sampled, and the binary values thereof have been thus accumulated, each correlation value is proportional to the degree that each of the separate phase displaced versions of said replica is in phase with said input signal.

Claim 5

Apparatus as defined in claim 2 wherein said accumulating means comprises a plurality of adder-subtracters, each connected to receive binary values from said converting means, and a plurality of registers, a given register connected to a given adder-subtracter for a given correlation value to be formed by accumulating said binary values, said given register being connected to receive the output of said given adder-subtracter, and to transmit to said given adder-subtracter the correlation value stored for addition or subtraction of a sample value received from said converting means under control of the sign of a given phase displaced version from said generating means.

Claim 6

Apparatus as defined in claim 2 wherein said accumulating means comprises a single adder-subtracter and a recirculating register of sufficient length to store in series said plurality of correlation values, said register being connected to receive the output of said single adder-subtracter, and to transmit to said adder-subtracter in sequence said correlation values for addition or subtraction of each binary value received from said converting means, each binary value being added or subtracted to each correlation value stored according to the sign of a different phase displaced version of said replica.