US3787774A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Filter circuitry
Assignee: Hewlett Packard GmbH Germany
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Filing: 1972-08-28
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Granted: 1974-01-22
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Expires: 1992-08-28
Abstract
Abstract Circuitry for filtering a distinct variable spectral component includes a band-rejection filter formed by a summing amplifier with a feedback loop and a bandpass-filter connected to one of its inputs. The summing amplifier is connected to form the difference between the unfiltered spectrum at one of its inputs and the spectrum component to be suppressed at another of its inputs. The summing amplifier delivers the filtered signal spectrum at its output. A control circuit locks the common center frequency of the bandpass and band-rejection filters to the frequency of the spectral component to be suppressed.
Inventors
- 👤 U Tietze
- 👤 E Courtin
- 👤 S Traub
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 03:01
CPC Classifications
H; H03; H03H; H03H11/00; H03H11/02; H03H11/04; H03H11/12; H03H11/1217
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
161 words
Circuitry for filtering a periodic component of selected frequency from an input spectrum comprising: a summing circuit having one input connected to receive an input spectrum to be filtered and having another input for producing an output as a selected combination of the signals applied to the inputs thereof; frequency-determining means connected in feedback relation between the output and said other input of the Summing circuit for providing a feedback signal to the summing circuit containing the frequency component to be filtered; phase comparison means having a first input connected to receive the input spectrum and having a second input connected to receive a signal representative of the frequency component to be filtered; and a control circuit connected to the phase comparison circuit and responsive to the phase difference of signals applied to the inputs of said phase comparison means for supplying an output to said frequency-determining means to adjust the frequency determined thereby to said frequency component to be filtered.
Claim 2
Dependent Claim
161 words
Circuitry for filtering a periodic component of selected frequency from an input spectrum comprising: a summing circuit having one input connected to receive an input spectrum to be filtered and having another input for producing an output as a selected combination of the signals applied to the inputs thereof; frequency-determining means connected in feedback relation between the output and said other input of the Summing circuit for providing a feedback signal to the summing circuit containing the frequency component to be filtered; phase comparison means having a first input connected to receive the input spectrum and having a second input connected to receive a signal representative of the frequency component to be filtered; and a control circuit connected to the phase comparison circuit and responsive to the phase difference of signals applied to the inputs of said phase comparison means for supplying an output to said frequency-determining means to adjust the frequency determined thereby to said frequency component to be filtered.
Claim 3
Dependent Claim
23 words
Circuitry as in claim 1 wherein the frequency-determining means includes an inverter and two integrators connected in cascade to form a resonant loop.
Claim 4
Dependent Claim
19 words
Circuitry as in claim 1 wherein a resistive element is connected between the frequency-determining means and the summing circuit.
Claim 5
Dependent Claim
13 words
Circuitry as in claim 1 wherein the summing circuit includes a summing amplifier.
Claim 6
Dependent Claim
12 words
Circuitry as in claim 1 wherein the control circuit includes an integrator.
Claim 7
Dependent Claim
25 words
Circuitry as in claim 2 wherein the frequency-determining means includes an output from said inverter for supplying said frequency component filtered from the input spectrum.
Claim 8
Dependent Claim
33 words
Circuitry as in claim 6 wherein the phase comparison means includes a first square wave former connected between the output of the frequency-determining means and the second input of the phase comparison means.
Claim 9
Dependent Claim
27 words
Circuitry as in claim 7 wherein a second square wave former is connected between the spectrum input and the first input of the phase comparison circuit means.
Claim 10
Dependent Claim
44 words
Circuitry as in claim 6 comprising: a first high-pass filter connected between the spectrum input and the first input of the phase comparison means; and a second high-pass filter connected between the second input and the output from said inverter of the frequency-determining means.
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) | 1977-01-21 | 1977-07-23 | 1978-01-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-01-21 | 1981-07-23 | 1982-01-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-01-21 | 1985-07-23 | 1986-01-22 | $7700.00 | Window Closed / Lapsed |