Patent US3795877A successfully refreshed from Google Patents.
US3795877A
Expired / Lapsed
US
⏱️ 0.0 years remaining
High q notch filter
Assignee: GTE Sylvania Inc
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Filing: 1973-04-30
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Granted: 1974-03-05
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Expires: 1993-04-30
Abstract
Abstract A notch filter having a first group of capacitors which are connected in recurring sequence to an input terminal by a first commutating switch. The other terminals of the first group of capacitors are connected in common through an operational amplifier to a second group of capacitors. A second commutating switch operates in synchronism with the first switch to connect each of the second capacitors in recurring sequence to a second operational amplifier. A first feedback resistance is connected from the output of the second amplifier to the input of the first amplifier, and a second resistance is connected between the input of the second amplifier and ground. A low pass filter section is connected between the output of the second amplifier and an output terminal to provide a smooth output signal. The notch filter provides maximum attenuation at the frequency of the commutating switches.
Inventors
- 👤 M Poole
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 10:36
CPC Classifications
H; H03; H03H; H03H11/00; H03H11/02; H03H11/04; H03H11/12; H03H11/1217
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
389 words
A notch filter for attenuating an input signal of a predetermined frequency more than input signals of frequencies less than or more than said predetermined frequency, said filter comprising in combination an input terminal adapted to receive input signals; an output terminal; a first section having an input connection connected to said input terminal and an output connection, said first section including a first switching means connected to one of said connections, and a first plurality of N capacitors each having one terminal connected to the first switching means and having the other terminals connected in common to the other of said connections, said first switching means being operable to connect the one terminal of any one capacitor at a time to said one connection thereby connecting the capacitor between the input and output connections of the first section; a second section having an input connection coupled to the output connection of the first section and an output connection, said second section including a second switching means connected to one of said connections, and a second plurality of N capacitors each having one terminal connected to the second switching means and having the other terminals connected in common to the other of said connections, said second switching means being operable to connect the one terminal of any one capacitor at a time to said one connection thereby connecting the capacitor between the input and output connections of the second section; an isolation amplifier having its input connected to the output connection of the second section and its output coupled to said output terminal; a first resistance connected between the output connection of the first section and the output of the isolation amplifier; a second resistance connected between the input of the isolation amplifier and a point of reference potential; and switch driving means connected to the first and second switching means for causing the first switching means to connect each of the first plurality of capacitors between the input and output connections of the first section in a recurring sequence which repeats at said predetermined frequency, and for causing the second switching means to connect each of the second plurality of capacitors between the input and output connections of the second section in a recurring sequence which repeats at said predetermined frequency in synchronism with said first switching means.
Claim 2
Dependent Claim
389 words
A notch filter for attenuating an input signal of a predetermined frequency more than input signals of frequencies less than or more than said predetermined frequency, said filter comprising in combination an input terminal adapted to receive input signals; an output terminal; a first section having an input connection connected to said input terminal and an output connection, said first section including a first switching means connected to one of said connections, and a first plurality of N capacitors each having one terminal connected to the first switching means and having the other terminals connected in common to the other of said connections, said first switching means being operable to connect the one terminal of any one capacitor at a time to said one connection thereby connecting the capacitor between the input and output connections of the first section; a second section having an input connection coupled to the output connection of the first section and an output connection, said second section including a second switching means connected to one of said connections, and a second plurality of N capacitors each having one terminal connected to the second switching means and having the other terminals connected in common to the other of said connections, said second switching means being operable to connect the one terminal of any one capacitor at a time to said one connection thereby connecting the capacitor between the input and output connections of the second section; an isolation amplifier having its input connected to the output connection of the second section and its output coupled to said output terminal; a first resistance connected between the output connection of the first section and the output of the isolation amplifier; a second resistance connected between the input of the isolation amplifier and a point of reference potential; and switch driving means connected to the first and second switching means for causing the first switching means to connect each of the first plurality of capacitors between the input and output connections of the first section in a recurring sequence which repeats at said predetermined frequency, and for causing the second switching means to connect each of the second plurality of capacitors between the input and output connections of the second section in a recurring sequence which repeats at said predetermined frequency in synchronism with said first switching means.
Claim 3
Dependent Claim
41 words
A notch filter in accordance with claim 1 including a low pass filter connected between the output of the isolation amplifier and the output terminal for filtering out high frequency switching transients and steps in the voltage levels of adjacent capacitors.
Claim 4
Dependent Claim
19 words
A notch filter in accordance with claim 2 wherein said isolation amplifier is an operational amplifier exhibiting unity gain.
Claim 5
Dependent Claim
37 words
A notch filter in accordance with claim 3 including a second isolation amplifier having its input connected to the output connection of the first section and its output connected to the input connection of the second section.
Claim 6
Dependent Claim
100 words
A notch filter in accordance with claim 4 wherein said first-mentioned isolation amplifier is an operational amplifier having an inverting input connection and a non-inverting input connection, the inverting input connection being connected to the output of the amplifier and the non-inverting input connection being connected to the output connection of the second section; and said second isolation amplifier is an operational amplifier having an inverting input connection and a non-inverting input connection, the inverting input connection being connected to the output of the amplifier and the non-inverting input connection being connected to the output connection of the first section.
Claim 7
Dependent Claim
251 words
A notch filter in accordance with claim 5 wherein said first switching means includes an analog switch having a single terminal connected to the one of said connections of the first section, a plurality of N terminals each of which is connected to one of the terminals of a different one of said first plurality of capacitors, and a group of control terminals; said first switching means being operable to connect said single terminal to any one of said plurality of terminals as determined by the combination of control signals applied at said control terminals; said second switching means includes an analog switch having a single terminal connected to the one of said connections of the second section, a plurality of N terminals each of which is connected to one of the terminals of a different one of said second plurality of capacitors, and a group of control terminals; said second switching means being operable to connect said single terminal to any one of said plurality of terminals as determined by the combination of control signals applied at said control terminals; and said switch driving means includes a digital counter connected to the control terminals of said first and second switching means and operable to count input pulses through a recurring sequence of N combinations of control signals, and a source of clock pulses connected to said digital counter for generating input pulses to be counted thereby, said clock pulses being generated at the rate of N times said predetermined frequency.
References Cited (Backward Citations)
US3403345A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-03-04 | 1977-09-03 | 1978-03-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-03-04 | 1981-09-03 | 1982-03-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-03-04 | 1985-09-03 | 1986-03-05 | $7700.00 | Window Closed / Lapsed |