Method and apparatus for detecting the presence of signal components of predetermined frequency in a multi-frequency signal

Claim 3

A method as claimed in claim 1, including: comparing at least the greater of the absolute values of said sums with a reference value; and conditioning said indication signal to be indicative of the presence of said component when the said at least thE greater absolute value exceeds said reference value.

Claim 4

A method as claimed in claim 1, including: summing absolute values of said sums; comparing such sum of sums with a reference value; and conditioning said indication signal to be indicative of the presence of said component when said sum of sums exceeds said reference valve.

Claim 5

A method as claimed in claim 1, including: squaring each said sum; summing the resultant squared sums; comparing such sum of the squared sums with a reference value; and conditioning said indication signal to be indicative of the presence of said component when said sum of the squares exceeds said reference value.

Claim 6

A method as claimed in claim 1, wherein said phase displacement is substantially pi /2.

Claim 7

Apparatus for determining whether a particular frequency component is present in a first sequence of pulse code modulated signals representing instantaneous time spaced values of a periodically varing signal of substantially constant amplitude, the apparatus comprising: a stored sequence generator for generating second and third sequences of digitally encoded signals respectively representing the instantaneous values, at time spacings corresponding to the time spacing of said values of said periodically varying signal, of separate ones of two test signals of said particular frequency, these test signals being of substantially square wave form but displaced relative to each other by a phase displacement other than 0 and pi ; two sign gates coupled to receive said first sequence of signals and respective separate ones of said second and third sequences of signals and operable to produce two further sequences of digitally encoded signals representing multiplicands of corresponding instantaneous values of the periodically varying signal and the respective phase displaced test signals; first and second accumulators coupled to receive respective separate ones of said further sequences of signals and to separately accumulate these; and component indicator means receiving the accumulated said further sequences of signals and deriving from these an indication signal which when said component is present is indicative of such presence.

Claim 8

Apparatus for determining whether a particular frequency component is present in a first sequence of pulse code modulated signals representing instantaneous time spaced values of a periodically varing signal of substantially constant amplitude, the apparatus comprising: a stored sequence generator for generating second and third sequences of digitally encoded signals respectively representing the instantaneous values, at time spacings corresponding to the time spacing of said values of said periodically varying signal, of separate ones of two test signals of said particular frequency, these test signals being of substantially square wave form but displaced relative to each other by a phase displacement other than 0 and pi ; two sign gates coupled to receive said first sequence of signals and respective separate ones of said second and third sequences of signals and operable to produce two further sequences of digitally encoded signals representing multiplicands of corresponding instantaneous values of the periodically varying signal and the respective phase displaced test signals; first and second accumulators coupled to receive respective separate ones of said further sequences of signals and to separately accumulate these; and component indicator means receiving the accumulated said further sequences of signals and deriving from these an indication signal which when said component is present is indicative of such presence.

Claim 9

Apparatus as claimed in claim 6, wherein said component indicator means includes a comparator for comparing at least the greater of the absolute values of said accumulated said further sequences of signals with a reference value to condition said indication signal to be indicative of the presence of said component when the said at least the greater absolute value exceeds said reference value.

Claim 10

Apparatus as claimed in claim 6, wherein said component indicator means includes; an adder coupled to both said first and second accumulators to receive said accumulated said further sequences of signals and to produce an output signal representing the sum of absolute values of said accumulated said further sequences; and comparator means coupled to said adder to receive said output signal and to compare it with a reference signal to condition said indication signal to indicate the presence of said component when said output signal exceeds said reference signal.

Claim 11

Apparatus as claimed in claim 6, wherein said component indicator means includes; two squaring multipliers, one coupled to each said accumulator, and these being operable to receive respective said accumulated said further sequences of signals and to produce respective signals representing the squares of the sums of the respective said accumulated said further sequences of signals; an adder coupled to said squaring multipliers to receive said signals representing the squares and to produce an output signal representing the sum of the squares; and comparator means coupled to said adder to receive said output signal and operable to compare with a reference value to condition said indication signal to be indicative of the presence of said component when said ouTput signal exceeds said reference value.

Claim 12

Apparatus for determining which one of a number of particular components of different predetermined frequencies within a given frequency range is present in a first sequence of pulse code modulated signals representing instantaneous time spaced values of a periodically varying signal of substantially constant amplitude, the apparatus comprising: a plurality of stored sequence generators operable to generate, for each said frequency component, second and third further sequences of digitally encoded signals respectively representing instantaneous values, at time spacings corresponding to the time spacing of said values of said periodically varying signal, of two test signals of the corresponding predetermined frequency, each such two test signals being of substantially square wave form but displaced relative to each other by a phase displacement other than 0 and pi ; a plurality of pairs of sign gates, each said pair being coupled to receive said first sequence of signals and to separately receive, one to each one of said pair, the second and third sequences of signals corresponding to a respective one of said predetermined frequencies, and to produce, for each pair, two further sequences of signals representing the multiplicands of the corresponding instantaneous values of the periodically varying wave form and the respective phase displaced test signals; a plurality of accumulators, one accumulator connected to receive the said further sequence of signals from a separate one of each of said sign gates, and each said accumulator operating to accumulate signals of the further sequence received thereby; and component indicator means coupled to receive the accumulated said further sequences and operable to derive from these an indication signal which indicates which of said components is present, in said first sequence of signals.

Claim 13

Apparatus for determining which one of a number of particular components of different predetermined frequencies within a given frequency range is present in a first sequence of pulse code modulated signals representing instantaneous time spaced values of a periodically varying signal of substantially constant amplitude, the apparatus comprising: a plurality of stored sequence generators operable to generate, for each said frequency component, second and third further sequences of digitally encoded signals respectively representing instantaneous values, at time spacings corresponding to the time spacing of said values of said periodically varying signal, of two test signals of the corresponding predetermined frequency, each such two test signals being of substantially square wave form but displaced relative to each other by a phase displacement other than 0 and pi ; a plurality of pairs of sign gates, each said pair being coupled to receive said first sequence of signals and to separately receive, one to each one of said pair, the second and third sequences of signals corresponding to a respective one of said predetermined frequencies, and to produce, for each pair, two further sequences of signals representing the multiplicands of the corresponding instantaneous values of the periodically varying wave form and the respective phase displaced test signals; a plurality of accumulators, one accumulator connected to receive the said further sequence of signals from a separate one of each of said sign gates, and each said accumulator operating to accumulate signals of the further sequence received thereby; and component indicator means coupled to receive the accumulated said further sequences and operable to derive from these an indication signal which indicates which of said components is present, in said first sequence of signals.

Claim 14

Apparatus as claimed in claim 10, wherein said component indicator means includes: a plurality of first comparators, each first comparator being coupled to the two accumulator means which are associated with a separate one of said pairs of sign gates and operating to receive the accumulated said further sequences of signals from these accumulators and to compare these and produce an encoded output signal representative of at least the absolute value of that of the accumulated said further sequences of signals applied thereto having the greater absolute value; and a second comparator coupled to all said first comparators to receive said output signals and operable to condition said indication signal to be indicative of the presence of a said component by identifying that one of said output signals which is of the greatest absolute value.

Claim 15

Apparatus as claimed in claim 10, wherein said component indicator means includes: a plurality of adders, each adder being coupled to the accumulator associated with a separate one of said pairs of said sign gates to receive the accumulated said further sequences of signals from these accumulators and being operable to produce a digitally encoded output signal representing the sum of the absolute values of the accumulated said further sequences of signals received thereby; and a comparator which is coupled to each said adder to receive all said output signals and operable to condition said indication signal to be indicative of the presence of a said component by identifying whichever of said output signals wich is greatest.

Claim 16

Apparatus as claimed in claim 10, wherein said component indicator means includes: a plurality of squaring multipliers, a separate one being coupled to each said accumulator to receive the accumulated said further sequence of signals therefrom and being operable to generate a signal representing the square of the respective said accumulated said further sequence of signals received thereby; a plurality of adders, each adder being coupled to the squaring multipliers associated with a separate one of said pairs of sign gates to receive the said signals representing the squares of the accumulated said further sequences of signals from these accumulators and being operable to add these to produce an output signal representing the sum of the squares of said accumulated said further sequences of signals applied thereto; and a comparator coupled to all said adders to receive the said output signals therefrom and operable to condition the said indication signal to be indicative of the presence of a said component by identifying that one of said output signals which is greatest.

Claim 19

A method as claimed in claim 14, wherein said indication signal is derived by: comparing, for each said component, the absolute values of the two corresponding accumulated said further sequences of signals to produce an output signal which is indicative of the magnitude of the greater of these absolute values; and then comparing the output signals for each said component to condition said indication signal to indicate the component which is present by identifying that of the output signals which is greatest.

Claim 20

A method as claimed in claim 14, wherein said indication signal is derived by: adding, for each said component, the absolute values of the two corresponding accumulated said further sequences of signals and generating a corresponding output signal representing at least the absolute values of these added accumulated sequences; and then comparing the absolute values of said output signals corresponding to all of the said components and conditioning said indication signal to indicate the component present in accordance with that of said output signals which has the greatest absolute value.

Claim 21

A method as claimed in claim 14, wherein said indication signal is derived by; first deriving, for the two accumulated said further sequences of signals corresponding to each frequency component, signals representing the squares of such accumulated further sequence; deriving, for each component an output signal representing the sum of the two corresponding signals representing squares; and conditioning said indication signal to indicate the component which is present by identifying that one of said output signals which is of greatest absolute value.