US3906218A
Expired / Lapsed
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Digital filters
Assignee: International Business Machines Corp
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Filing: 1974-12-03
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Granted: 1975-09-16
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Expires: 1994-12-03
Abstract
Abstract A redesigned digital filter is disclosed which uses fewer of the costly multiplier components than conventional digital filters. Samples of the input signals are processed alternately using a multiplier common to two successive samples and a correction term is generated using successive pairs of input samples. The generation of the correction term requires fewer than one-half of the multiplier circuits used in a conventional filter so that the overall circuit saves about one-fourth of the multipliers usually needed.
Inventors
- 👤 Henri J Nussbaumer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 07:17
CPC Classifications
H; H03; H03H; H03H17/00; H03H17/02; H03H17/0223; H03H17/0225
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
356 words
An electrical filter of the sampling type wherein each output signal sample is derived from a plurality of weighted earlier input signal samples, said filter characterized by having: a. a first means for forming a main term, said first means including: i. summing means for adding the value of each input signal sample to that of the preceding input signal sample; ii. storage means for temporarily storing at least the last n sums provided by said summing means; iii. readout means for providing the value of every second sum temporarily stored by said storage means; iv. means for weighting every second sum provided by said readout means, by alternatively using the sums of even order to form a first output sample and the sums of odd order to form a second output sample; and v. means for adding together the sums weighted by said weighting means and associated with the output signal sample being derived; b. a second means for forming a corrective term, including: i. a second storage means for temporarily storing the last n signal samples applied to the input of said filter; ii. another means for providing the value of every second sample temporarily stored in said second storage; iii. product means for weighting the values of the samples provided by said another means, by alternately using a first set of coefficients selected from the coefficients of the filter to be realized while forming a third output signal sample and a second set of coefficients while forming the fourth output sample; iv. adder means for adding together the samples weighted by said product means while forming each output signal sample; v. a last storage means for storing the result of the operation performed by said adder means when the output sample preceding the sample being processed was generated; and vi. means for inverting the content of said last storage means and adding the inverted content to the term provided by said adder means; and c. another adder means for adding together said main term and said corrective term provided by said first and second means, respectively, to provide a filtered output signal sample.
Claim 2
Dependent Claim
356 words
An electrical filter of the sampling type wherein each output signal sample is derived from a plurality of weighted earlier input signal samples, said filter characterized by having: a. a first means for forming a main term, said first means including: i. summing means for adding the value of each input signal sample to that of the preceding input signal sample; ii. storage means for temporarily storing at least the last n sums provided by said summing means; iii. readout means for providing the value of every second sum temporarily stored by said storage means; iv. means for weighting every second sum provided by said readout means, by alternatively using the sums of even order to form a first output sample and the sums of odd order to form a second output sample; and v. means for adding together the sums weighted by said weighting means and associated with the output signal sample being derived; b. a second means for forming a corrective term, including: i. a second storage means for temporarily storing the last n signal samples applied to the input of said filter; ii. another means for providing the value of every second sample temporarily stored in said second storage; iii. product means for weighting the values of the samples provided by said another means, by alternately using a first set of coefficients selected from the coefficients of the filter to be realized while forming a third output signal sample and a second set of coefficients while forming the fourth output sample; iv. adder means for adding together the samples weighted by said product means while forming each output signal sample; v. a last storage means for storing the result of the operation performed by said adder means when the output sample preceding the sample being processed was generated; and vi. means for inverting the content of said last storage means and adding the inverted content to the term provided by said adder means; and c. another adder means for adding together said main term and said corrective term provided by said first and second means, respectively, to provide a filtered output signal sample.
Claim 3
Dependent Claim
385 words
An electrical filter of the sampling type wherein each output signal sample is derived from a plurality of weighted earlier input signal samples, said filter characterized in that it includes: a. a first means for forming a main term, said first means including: i. summing means for adding each signal sample fed to the input of the filter and the preceding input signal sample; ii. a first delay line; iii. means for sequentially feeding the sums resulting from the operation performed by said summing means to said first delay line; iv. readout means for providing the value of every second sum stored in said first delay line; v. product means for weighting every second sum provided by said readout means, by alternatively using the values appearing at the readout means of even order to form a first output signal sample and the values appearing at the readout means of odd order to form a second output signal sample; and vi. means for adding together the weighted sums; b. a second means for forming a corrective term, said second means including: i. a second delay line into which representations of the input signal samples applied to the filter are sequentially entered; ii. taps on said second delay line to read out the representation of every second sample stored in said second delay line; iii. multiplying means for weighting the representations of samples appearing at said taps, using a first set of constants selected from the filter coefficients; iv. anotHer adding means for adding together the values of the samples weighted by said multiplying means; v. an inverter to generate the complement values of the output of said another adding means; vi. gating circuits to apply a second set of constants selected from the filter coefficients to said weighting means during the time the other samples are present at said taps; vii. a delay means to delay the inverted result of the operation performed by said another adding means until the time the output signal sample preceding the sample being processed is formed; viii. summation means for completing said corrective term by adding together the results provided by said another adding means and said delay means; and c. third summing means for forming the desired output signal sample by adding said corrective term to said main term.
Claim 4
Dependent Claim
385 words
An electrical filter of the sampling type wherein each output signal sample is derived from a plurality of weighted earlier input signal samples, said filter characterized in that it includes: a. a first means for forming a main term, said first means including: i. summing means for adding each signal sample fed to the input of the filter and the preceding input signal sample; ii. a first delay line; iii. means for sequentially feeding the sums resulting from the operation performed by said summing means to said first delay line; iv. readout means for providing the value of every second sum stored in said first delay line; v. product means for weighting every second sum provided by said readout means, by alternatively using the values appearing at the readout means of even order to form a first output signal sample and the values appearing at the readout means of odd order to form a second output signal sample; and vi. means for adding together the weighted sums; b. a second means for forming a corrective term, said second means including: i. a second delay line into which representations of the input signal samples applied to the filter are sequentially entered; ii. taps on said second delay line to read out the representation of every second sample stored in said second delay line; iii. multiplying means for weighting the representations of samples appearing at said taps, using a first set of constants selected from the filter coefficients; iv. anotHer adding means for adding together the values of the samples weighted by said multiplying means; v. an inverter to generate the complement values of the output of said another adding means; vi. gating circuits to apply a second set of constants selected from the filter coefficients to said weighting means during the time the other samples are present at said taps; vii. a delay means to delay the inverted result of the operation performed by said another adding means until the time the output signal sample preceding the sample being processed is formed; viii. summation means for completing said corrective term by adding together the results provided by said another adding means and said delay means; and c. third summing means for forming the desired output signal sample by adding said corrective term to said main term.
Claim 5
Independent Claim
481 words
A device for forming samples Yi and Wi of two signals Y and W derived from a sequence of samples of an input signal X through a first and a second filter, said filters having a first set, a1-an, of coefficients for said first filter and a second set, b1-bn, of coefficients, for said second filter, respectively, characterized in that said device includes: a. a first means for forming a main term, including: i. summing means for adding the value of each sample of the input signal to the value of the preceding sample; ii. value holding means for sequentially storing the output values provided by said summing means; iii. readout means for providing the value of every second value stored by said summing means; iv. multiplying means for weighting the values provided by said readout means with said coefficients a1-an belonging to said first set; and b. a second means for forming two corrective terms associated with said signals Y and W, respectively, said second means comprising; i. storage means for sequentially storing the values of the samples of input signal X applied to the input; ii. tap means for providing the value of every second sample stored by said storage means; iii. a first corrector means for forming the sum Yi1 of the samples provided by said tap means by weighting said samples with the odd order coefficients of said second set and summing said weighted samples; and iv. a second corrector means for forming the sum Wi 12 of the samples provided by said tap means by weighting said samples with the even order coefficients of said second set; c. a third means for alternating the sets of coefficients used by said first and second means for forming a sample of said signal Y and said signal W; d. a fourth means for storing the values provided by said second means, from the time a sample of Y and W is formed until the time the next sample is formed; e. a fifth means for forming an output sample Yi by adding the value of the term Yi2 formed using the even order coefficients of said first set of coefficients, as stored by said fourth means, to the term Yi1 provided by said second means; f. a sixth means for forming an output sample Wi by subtracting said second corrector term obtained by using the coefficients in said second set, said term being provided by said fourth means, from the result obtained by subtracting the term Wi 12 from the main term Zi(w); and g. seventh means for repeating the operations performed by said above means, by alternating the two sets of coefficients and the values of the terms of the Y and W forms while switching from the forming of samples Yi and Wi, to the forming of the next samples, namely, Yi 1 and Wi 1.
Claim 6
Independent Claim
481 words
A device for forming samples Yi and Wi of two signals Y and W derived from a sequence of samples of an input signal X through a first and a second filter, said filters having a first set, a1-an, of coefficients for said first filter and a second set, b1-bn, of coefficients, for said second filter, respectively, characterized in that said device includes: a. a first means for forming a main term, including: i. summing means for adding the value of each sample of the input signal to the value of the preceding sample; ii. value holding means for sequentially storing the output values provided by said summing means; iii. readout means for providing the value of every second value stored by said summing means; iv. multiplying means for weighting the values provided by said readout means with said coefficients a1-an belonging to said first set; and b. a second means for forming two corrective terms associated with said signals Y and W, respectively, said second means comprising; i. storage means for sequentially storing the values of the samples of input signal X applied to the input; ii. tap means for providing the value of every second sample stored by said storage means; iii. a first corrector means for forming the sum Yi1 of the samples provided by said tap means by weighting said samples with the odd order coefficients of said second set and summing said weighted samples; and iv. a second corrector means for forming the sum Wi 12 of the samples provided by said tap means by weighting said samples with the even order coefficients of said second set; c. a third means for alternating the sets of coefficients used by said first and second means for forming a sample of said signal Y and said signal W; d. a fourth means for storing the values provided by said second means, from the time a sample of Y and W is formed until the time the next sample is formed; e. a fifth means for forming an output sample Yi by adding the value of the term Yi2 formed using the even order coefficients of said first set of coefficients, as stored by said fourth means, to the term Yi1 provided by said second means; f. a sixth means for forming an output sample Wi by subtracting said second corrector term obtained by using the coefficients in said second set, said term being provided by said fourth means, from the result obtained by subtracting the term Wi 12 from the main term Zi(w); and g. seventh means for repeating the operations performed by said above means, by alternating the two sets of coefficients and the values of the terms of the Y and W forms while switching from the forming of samples Yi and Wi, to the forming of the next samples, namely, Yi 1 and Wi 1.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-09-15 | 1979-03-17 | 1979-09-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-09-15 | 1983-03-17 | 1983-09-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-09-15 | 1987-03-17 | 1987-09-16 | $7700.00 | Window Closed / Lapsed |