System for measuring amplitude of noise-contaminated periodic signal

Claim 1

A method of measuring the amplitude of a periodic signal of generally known frequency and unknown phase arriving from a remote source in the presence of a substantial noise level, comprising the steps of: (a) periodically extracting a first sample from the arriving signal at instants spaced substantially a whole number of signal cycles apart; (b) periodically extracting a second sample from the arriving signal at instants offset by a quarter-cycle from the instants of extraction of said first sample; (c) accumulating said first sample over N consecutive occurrences thereof to obtain a first algebraic sum, N being an integer greater than 1; (d) accumulating said second sample over N consecutive occurrences thereof to obtain a second algebraic sum; (e) comparing the signs of said algebraic sums to determine whether or not the instants of extraction of said first and second samples lie in the same half-cycle of the signal; (f) codirectionally shifting the instants of extraction within a signal cycle, by a corrective phase increment whose sign depends on the result of the comparison in step (e), to make the occurrences of said first and second samples more nearly coincident with a peak and a zero crossing of the arriving signal, respectively; and (g) upon substantial disappearance of said second sum, deriving from said first algebraic sum the absolute magnitude of the signal amplitude.

Claim 2

A method of measuring the amplitude of a periodic signal of generally known frequency and unknown phase arriving from a remote source in the presence of a substantial noise level, comprising the steps of: (a) periodically extracting a first sample from the arriving signal at instants spaced substantially a whole number of signal cycles apart; (b) periodically extracting a second sample from the arriving signal at instants offset by a quarter-cycle from the instants of extraction of said first sample; (c) accumulating said first sample over N consecutive occurrences thereof to obtain a first algebraic sum, N being an integer greater than 1; (d) accumulating said second sample over N consecutive occurrences thereof to obtain a second algebraic sum; (e) comparing the signs of said algebraic sums to determine whether or not the instants of extraction of said first and second samples lie in the same half-cycle of the signal; (f) codirectionally shifting the instants of extraction within a signal cycle, by a corrective phase increment whose sign depends on the result of the comparison in step (e), to make the occurrences of said first and second samples more nearly coincident with a peak and a zero crossing of the arriving signal, respectively; and (g) upon substantial disappearance of said second sum, deriving from said first algebraic sum the absolute magnitude of the signal amplitude.

Claim 8

A system for measuring the amplitude of a periodic signal of generally known frequency and unknown phase arriving from a remote source in the presence of a substantial noise level, comprising: input means arranged to receive the arriving signal; sampling means connected to said input means; timing means controlling said sampling means for periodically extracting pairs of consecutive samples from respective cycles of the arriving signal, each pair consisting of a first and a second sample offset from each other by a quarter-cycle; first accumulating means connected to said sampling means and controlled by said timing means for integrating N consecutive occurrences of said first sample into a first algebraic sum, N being an integer greater than 1; second accumulating means connected to said sampling means and controlled by said timing means for integrating N consecutive occurrences of said second sample into a second algebraic sum; comparison means connected to said first and second accumulating means for modifying the operation of said timing means after every N occurrences of said pairs to shift the instants of extraction of said samples within a cycle, by a corrective phase increment, in one sense upon said algebraic sums being of the same sign and in the opposite sense upon said algebraic sums being of different signs to make the occurrences of said first and second samples more nearly coincident with a peak and a zero crossing of the arriving signal, respectively; and indicator means connected to said first accumulating means for deriving a measure of the amplitude of the arriving signal from said first algebraic sum upon substantial disappearance of said second algebraic sum.

Claim 9

A system for measuring the amplitude of a periodic signal of generally known frequency and unknown phase arriving from a remote source in the presence of a substantial noise level, comprising: input means arranged to receive the arriving signal; sampling means connected to said input means; timing means controlling said sampling means for periodically extracting pairs of consecutive samples from respective cycles of the arriving signal, each pair consisting of a first and a second sample offset from each other by a quarter-cycle; first accumulating means connected to said sampling means and controlled by said timing means for integrating N consecutive occurrences of said first sample into a first algebraic sum, N being an integer greater than 1; second accumulating means connected to said sampling means and controlled by said timing means for integrating N consecutive occurrences of said second sample into a second algebraic sum; comparison means connected to said first and second accumulating means for modifying the operation of said timing means after every N occurrences of said pairs to shift the instants of extraction of said samples within a cycle, by a corrective phase increment, in one sense upon said algebraic sums being of the same sign and in the opposite sense upon said algebraic sums being of different signs to make the occurrences of said first and second samples more nearly coincident with a peak and a zero crossing of the arriving signal, respectively; and indicator means connected to said first accumulating means for deriving a measure of the amplitude of the arriving signal from said first algebraic sum upon substantial disappearance of said second algebraic sum.