Frequency sensing device for reducing non-periodic components

Claim 1

A device for generating an electrical signal having a periodic component representative of a periodic component of an electrical input signal and containing fewer non-periodic components than the electrical input signal, the device comprising autocorrelation means having a first series of stages for storing information, means for applying the electrical input signal or a signal representing variation with time of an electrical parameter of the input signal to an input to said autocorrelation means, means for periodically causing information representing the electrical parameter at said input to enter a first stage in said first series of stages and advancing information in each said stage to a respective next succeeding stage, and means which, in the interval of time between each entry of information into said first stage and the next succeeding entry of information, generate a series of comparison signals, each of the comparison signals being a logic level representing a comparison between information stored at a pair of associated stages in said first series of stages, and means for generating from each series of comparison signals an output representing a sum of the comparison signals in the series, said first series of stages being so associated together in pairs and the comparisons being such that there is generated at the output of said generating means an output signal having a periodic component whose period is equal to half the period of a periodic component in the input signal and having substantially fewer non-periodic components than the input signal.

Claim 2

A device for generating an electrical signal having a periodic component representative of a periodic component of an electrical input signal and containing fewer non-periodic components than the electrical input signal, the device comprising autocorrelation means having a first series of stages for storing information, means for applying the electrical input signal or a signal representing variation with time of an electrical parameter of the input signal to an input to said autocorrelation means, means for periodically causing information representing the electrical parameter at said input to enter a first stage in said first series of stages and advancing information in each said stage to a respective next succeeding stage, and means which, in the interval of time between each entry of information into said first stage and the next succeeding entry of information, generate a series of comparison signals, each of the comparison signals being a logic level representing a comparison between information stored at a pair of associated stages in said first series of stages, and means for generating from each series of comparison signals an output representing a sum of the comparison signals in the series, said first series of stages being so associated together in pairs and the comparisons being such that there is generated at the output of said generating means an output signal having a periodic component whose period is equal to half the period of a periodic component in the input signal and having substantially fewer non-periodic components than the input signal.

Claim 7

A device as claimed in claims 3 or 4, including additionally means for determining the period of the periodic component in the signal at the otuput of the means for generating.

Claim 19

A device as claimed in 8, comprising a qualifier circuit, and means for applying outputs of the comparator means to the qualifier circuit, the qualifier circuit being adapted to produce a predetermined output signal only if a first predetermined number of successive outputs applied to the qualifier circuit from the comparator means include at least a second predetermined number of predetermined outputs.

Claim 21

A device as claimed in claims 1 or 2, wherein the autocorrelation means further comprise a second series of stages having an associated means which generate series of comparison signals and an associated means for generating sums of comparison signals, an input to said second series of stages being connected to an output of the generating means associated with the first series of stages, whereby there is generated at the output of the generating means associated with the second series of stages an output having a periodic component whose period is equal to one quarter of the period of a periodic component in the input signal.

Claim 22

A device as claimed in claims 1 or 2, including additionally means for determining the period of the periodic component in the signal at the output of said means for generating.

Claim 32

A device for generating an electrical signal having a periodic component representative of a periodic component of an electrical input signal and containing fewer non-periodic components than the electrical input signal, the device comprising an amplitude limiter which, when the electrical input signal is applied thereto, generates a signal whose amplitude assumes one of two predetermined logic levels, a shift register, the shift register having a series of stages for storing information in the form of either one of the two logic levels, means for applying the signal from the amplitude limiter to an input to a first of the stages in the shift register, means for periodically causing the logic level of the signal at the input to said first stage to enter that stage and advancing the logic level in each stage to a respective next succeeding stage, gating means having a pair of inputs connected to respective stages in each of a series of pairs of associated stages, the two stages in each pair of associated stages being equidistantly spaced from a predetermined position in the register, multiplexer means for successively applying to one input of the gating means the logic level stored in a first of each pair of associated stages and for successively applying to the other input of the gating means the logic level stored in a second of each pair of associated stages, whereby, there is generated at the output of the gating means a comparison signal in the form of a first logic level if the logic levels in a pair of associated stages are the same and a comparison signal in the form of a second logic level if the logic levels in a pair of associated stages are different, two counters each having an input connected to an output of the gating means, a first counter being adapted to count the number of comparison signals in each series which are of the first logic level and a second counter being adapted to count the number of comparison signals in each series which are of the second logic level, and means for generating an output which is a first or second logic level according to whether a count recorded by the first counter is greater than or smaller than the associated count recorded by the other counter by a predetermined number, the outputs of the first or second logic level forming an output signal having a periodic component whose period is equal to half the period of a periodic component in the input signal.

Claim 33

A device for generating an electrical signal having a periodic component representative of a periodic component of an electrical input signal and containing fewer non-periodic components than the electrical input signal, the device comprising an amplitude limiter which, when the electrical input signal is applied thereto, generates a signal whose amplitude assumes one of two predetermined logic levels, a shift register, the shift register having a series of stages for storing information in the form of either one of the two logic levels, means for applying the signal from the amplitude limiter to an input to a first of the stages in the shift register, means for periodically causing the logic level of the signal at the input to said first stage to enter that stage and advancing the logic level in each stage to a respective next succeeding stage, gating means having a pair of inputs connected to respective stages in each of a series of pairs of associated stages, the two stages in each pair of associated stages being equidistantly spaced from a predetermined position in the register, multiplexer means for successively applying to one input of the gating means the logic level stored in a first of each pair of associated stages and for successively applying to the other input of the gating means the logic level stored in a second of each pair of associated stages, whereby, there is generated at the output of the gating means a comparison signal in the form of a first logic level if the logic levels in a pair of associated stages are the same and a comparison signal in the form of a second logic level if the logic levels in a pair of associated stages are different, two counters each having an input connected to an output of the gating means, a first counter being adapted to count the number of comparison signals in each series which are of the first logic level and a second counter being adapted to count the number of comparison signals in each series which are of the second logic level, and means for generating an output which is a first or second logic level according to whether a count recorded by the first counter is greater than or smaller than the associated count recorded by the other counter by a predetermined number, the outputs of the first or second logic level forming an output signal having a periodic component whose period is equal to half the period of a periodic component in the input signal.