US4068309A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method and device for detecting two different frequency amplitude and phase signals in a combined digital signal
Assignee: DE STAAT DER NEDERLANDEN TE DEZEN VERTEGENWOORDIGD DOOR DE DIRECTEUR-GENERAAL DER POSTERIJEN TELEGRAFIE EN TELEFONIE
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Filing: 1976-11-15
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Granted: 1978-01-10
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Expires: 1996-11-15
Abstract
Abstract Method for detecting, in a combined digital signal, the presence of two signals differing in frequency, amplitude and phase and having frequencies occurring in a known series. Samples of the combined signal are multiplied by samples of only one derivative of each of the frequencies of the known series. This derivative is formed by the product of a modulating factor formed by the samples of a frequency which is the sum or the difference of (a) a fixed frequency of 2000 Hz and the frequency to be detected in the known series and (b) a factor allowing a filtering at the said fixed frequency and formed by the samples of the sine of the fixed frequency shifted by 45°. These products are alternately stored in accumulators until after a certain time the presence of certain frequencies is deduced from the sum of the products in the accumulators by means of comparison.
Inventors
- 👤 Chaim Zalman Drukarch
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 16:10
CPC Classifications
H; H04; H04Q; H04Q1/00; H04Q1/18; H04Q1/30; H04Q1/44; H04Q1/444; H04Q1/45; H04Q1/457; H04Q1/4575
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
167 words
A method for detecting, in a combined digital signal, the presence of two signals differing in frequency, amplitude, and phase and having frequencies occurring in a known series, said method comprising: multiplying samples of the combined signal by samples of at least one derivative of always one of the frequencies of the known series; storing the resulting products in accumulators, and then after a certain time deducing the presence of certain frequencies from the sum of the products in the accumulators by means of comparison; wherein: said samples of the combined signal are multiplied by the samples of only one derivative per frequency; wherein said derivative is formed by the product of a modulating factor formed by the samples of a frequency which is the algebraic sum of a fixed frequency of 2000 Hz and the frequency to be detected in the known series; wherein the sine of said fixed frequency is shifted by 45°; and further wherein said fixed frequency is filtered out by said comparison.
Claim 2
Independent Claim
167 words
A method for detecting, in a combined digital signal, the presence of two signals differing in frequency, amplitude, and phase and having frequencies occurring in a known series, said method comprising: multiplying samples of the combined signal by samples of at least one derivative of always one of the frequencies of the known series; storing the resulting products in accumulators, and then after a certain time deducing the presence of certain frequencies from the sum of the products in the accumulators by means of comparison; wherein: said samples of the combined signal are multiplied by the samples of only one derivative per frequency; wherein said derivative is formed by the product of a modulating factor formed by the samples of a frequency which is the algebraic sum of a fixed frequency of 2000 Hz and the frequency to be detected in the known series; wherein the sine of said fixed frequency is shifted by 45°; and further wherein said fixed frequency is filtered out by said comparison.
Claim 3
Independent Claim
133 words
A device for detecting in a combined signal, the presence of two signals differing in frequency, amplitude, and phase, and having frequencies occurring in a known series, said device including a circuit for each frequency to be detected, said circuit comprising: a store (g) for recording one of the frequencies of the known series multiplied by a fixed frequency, a gate (t) for the multiplication of the said stored frequency by the signal to be detected, two accumulators (a, b) for alternately recording the output signal of said gate (t), a totalizator (c) for adding, after some time, the absolute values of the contents of said accumulators (a, b), and a device (V) for comparing the results of the totalizators for each of said different frequencies and for indicating the frequencies hunted for.
Claim 4
Independent Claim
133 words
A device for detecting in a combined signal, the presence of two signals differing in frequency, amplitude, and phase, and having frequencies occurring in a known series, said device including a circuit for each frequency to be detected, said circuit comprising: a store (g) for recording one of the frequencies of the known series multiplied by a fixed frequency, a gate (t) for the multiplication of the said stored frequency by the signal to be detected, two accumulators (a, b) for alternately recording the output signal of said gate (t), a totalizator (c) for adding, after some time, the absolute values of the contents of said accumulators (a, b), and a device (V) for comparing the results of the totalizators for each of said different frequencies and for indicating the frequencies hunted for.
Claim 5
Dependent Claim
13 words
A device according to claim 2 wherein said fixed frequency is 2000 Hz.
Claim 6
Dependent Claim
16 words
A device according to claim 2 wherein said fixed frequency in said store is shifted 45°.
Claim 7
Dependent Claim
17 words
A device according to claim 2 wherein said comparing device includes a filter for said fixed frequency.
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) | 1981-01-09 | 1981-07-11 | 1982-01-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-01-09 | 1985-07-11 | 1986-01-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-01-09 | 1989-07-11 | 1990-01-10 | $7700.00 | Window Closed / Lapsed |