US4707653A — Frequency measurement circuit

Claim 1

Independent Claim 139 words

A frequency measurement circuit comprising: a source of input pulse signals; means for producing a measured frequency signal indicative of the frequency of the input pulse signals; first channel means receiving said measured frequency signal for producing an averaged frequency signal corresponding to the average of a selected number of the measured frequency signals; second channel means coupled to receive said measured frequency signal and said averaged frequency signal for generating a difference error signal indicative of the difference between the signals; said second channel means includes means for producing a variable threshold, which threshold is increased if the difference error signal is greater than the threshold and decreased if it is less than the threshold; and said first channel means includes means for updating the averaged frequency signal when the difference error signal is less than the threshold.

Claim 2

Dependent Claim 139 words

A frequency measurement circuit comprising: a source of input pulse signals; means for producing a measured frequency signal indicative of the frequency of the input pulse signals; first channel means receiving said measured frequency signal for producing an averaged frequency signal corresponding to the average of a selected number of the measured frequency signals; second channel means coupled to receive said measured frequency signal and said averaged frequency signal for generating a difference error signal indicative of the difference between the signals; said second channel means includes means for producing a variable threshold, which threshold is increased if the difference error signal is greater than the threshold and decreased if it is less than the threshold; and said first channel means includes means for updating the averaged frequency signal when the difference error signal is less than the threshold.

Claim 3

Dependent Claim 27 words

The circuit of claim 1 wherein said means for producing a variable threshold includes a comparator for comparing a current threshold value with said difference error signal.

Claim 4

Dependent Claim 37 words

The circuit of claim 2 wherein the means for producing a variable threshold further includes: an absolute value circuit coupled to the input of said comparator; and an up/down counter coupled to the output of the comparator.

Claim 5

Dependent Claim 25 words

The circuit of claim 1 wherein said means for producing the measured frequency signal includes: a pulse counter; and a register coupled to said counter.

Claim 6

Dependent Claim 17 words

The circuit of claim 4 wherein said counter and register are timed by a fixed reference clock.

Claim 7

Dependent Claim 22 words

The circuit of claim 1 wherein said means for producing the measured frequency signal includes a 1/X function programmed read only memory.

Claim 8

Dependent Claim 23 words

The circuit of claim 1 wherein said first channel means includes: averaging filter means coupled at its output to the second channel means.

Claim 9

Dependent Claim 56 words

The circuit of claim 7 wherein the averaging filter means includes: a first constant multiplier; an adder coupled to the first constant multiplier; a register coupled to the adder for supplying the averaged frequency signal; and a second constant multiplier, which is complementary to said first constant multiplier, coupled from the register back to the adder.

Claim 10

Dependent Claim 34 words

The circuit of claim 7 further including a logic circuit coupled to receive the difference error signal and for enabling the averaging filter means when said difference error signal is less than the threshold.

Claim 11

Independent Claim 108 words

A system for processing pulse signals while rejecting noise in the signals, comprising: means for measuring the frequency of the pulse signals; means for averaging the frequency values of a number of preceding pulse signals; means for subtracting said averaged signal from a measured signal and for generating a difference error signal indicative of the difference; means for generating a threshold value and for adjusting such threshold value in response to said difference error signal; and wherein the measured signal that has a frequency value greater than said threshold value is rejected and that which has a value below said threshold value is used to adjust the threshold.

Claim 12

Independent Claim 108 words

A system for processing pulse signals while rejecting noise in the signals, comprising: means for measuring the frequency of the pulse signals; means for averaging the frequency values of a number of preceding pulse signals; means for subtracting said averaged signal from a measured signal and for generating a difference error signal indicative of the difference; means for generating a threshold value and for adjusting such threshold value in response to said difference error signal; and wherein the measured signal that has a frequency value greater than said threshold value is rejected and that which has a value below said threshold value is used to adjust the threshold.

Claim 13

Dependent Claim 106 words

A circuit for adaptively measuring the frequency of pulse signals while rejecting noise, comprising: means for providing a measured frequency signal corresponding to the frequency of the pulse signals; means coupled to the providing means for supplying an averaged frequency signal from the measured frequency signals, which averaged frequency signal corresponds to the output signal of the circuit; and threshold means coupled to the providing means and to the supplying means for generating a variable threshold which is increased if the combined measured frequency and averaged frequency signals are greater than the threshold, and which is decreased if the combined signals are less than the threshold.

Claim 14

Dependent Claim 106 words

A circuit for adaptively measuring the frequency of pulse signals while rejecting noise, comprising: means for providing a measured frequency signal corresponding to the frequency of the pulse signals; means coupled to the providing means for supplying an averaged frequency signal from the measured frequency signals, which averaged frequency signal corresponds to the output signal of the circuit; and threshold means coupled to the providing means and to the supplying means for generating a variable threshold which is increased if the combined measured frequency and averaged frequency signals are greater than the threshold, and which is decreased if the combined signals are less than the threshold.

Claim 15

Dependent Claim 40 words

The circuit of claim 11 wherein: said threshold means provides a threshold which is indicative of the measured frequency signal being valid; and said supplying means updates the averaged frequency signal when the combined signals are less than said threshold.

Claim 16

Dependent Claim 63 words

The circuit of claim 11 wherein the threshold means includes: means for subtracting the averaged frequency signal from the measured frequency signal to provide a difference error signal; comparator means coupled to the means for subtracting; and counter means coupled from the output back to the input of the comparator means for generating the variable threshold in response to the difference error signal.

Claim 17

Dependent Claim 34 words

The circuit of claim 13 including: logic means coupled from the comparator means to the supplying means for enabling the latter in response to the difference error signal being less than the variable threshold.

Claim 18

Dependent Claim 55 words

The circuit of claim 11 wherein the means for supplying the averaged frequency signal includes: an adder means for receiving the measured frequency signal; register means coupled to the adder means for supplying the averaged frequency signal as the output signal; and constant multiplier means coupled from the register means output to the adder means.

Claim 19

Independent Claim 87 words

A method of measuring the frequency of a signal while rejecting spurious noise in the signal, comprising: measuring the frequency of an input pulse signal to provide a measured signal; producing an averaged signal representative of a time average of said measured signal; subtracting said averaged signal from said measured signal to generate a difference error signal; establishing a variable threshold value indicative of said difference error signal; and decreasing the threshold value in response to the difference error signal being less than the variable threshold value.

Claim 20

Independent Claim 87 words

A method of measuring the frequency of a signal while rejecting spurious noise in the signal, comprising: measuring the frequency of an input pulse signal to provide a measured signal; producing an averaged signal representative of a time average of said measured signal; subtracting said averaged signal from said measured signal to generate a difference error signal; establishing a variable threshold value indicative of said difference error signal; and decreasing the threshold value in response to the difference error signal being less than the variable threshold value.

Claim 21

Dependent Claim 45 words

The method of claim 16 wherein the step of establishing the threshold value comprises: incrementing said threshold value when the error signal has a value greater than the threshold value; and decrementing said threshold value when said error signal is less than the threshold value.

Claim 22

Dependent Claim 39 words

The method of claim 17 including: generating an enabling logic signal when the error signal is less than the threshold value; and enabling the step of producing in response to the enabling logic signal to update the averaged signal.

Claim 23

Dependent Claim 28 words

The method of claim 18 including: combining the previous averaged signal with the current measured signal in response to the enabling logic signal to update the averaged signal.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1990-11-16	1991-05-18	1991-11-17	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1994-11-16	1995-05-18	1995-11-17	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1998-11-16	1999-05-18	1999-11-17	$7700.00	Window Closed / Lapsed

Frequency measurement circuit

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