Patent US3707685A successfully refreshed from Google Patents.
US3707685A
Expired / Lapsed
US
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Q-invariant active filters
Assignee: Westinghouse Electric Corp
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Filing: 1970-05-21
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Granted: 1972-12-26
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Expires: 1990-05-21
Abstract
Abstract Three-amplifier Q-invariant active filters having three forms; low pass, band pass and high pass. In each form, the element values are preselected to provide zero sensitivity of the pole Q to the frequency-determining passive elements.
Inventors
- 👤 Philip R Geffe
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 15:32
CPC Classifications
H; H03; H03H; H03H11/00; H03H11/02; H03H11/04; H03H11/12; H03H11/1217
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
201 words
A Q-invariant active filter comprising, in combination: first, second, and third amplifier means each including input means and output means; an input impedance connecting an input signal to the input means of said first amplifier means; a fIrst resistance feedback element connecting the output means of said first amplifier means to the input means of said first amplifier means; first resistive means connecting the output means of said first amplifier means to the input means of said second amplifier means; first capacitive means connecting the input means of said second amplifier means to a point of reference potential; second resistive means connecting the output means of said second amplifier means to the input means of said third amplifier means; second capacitive means connecting the input means of said third amplifier means to a point of reference potential; a second resistance feedback element connecting the output means of said third amplifier means to the input means of said first amplifier means; and wherein the product of the gain of said second and third amplifier means and the ratio of the first resistance feedback element to the second resistance feedback element is substantially equal to (4Q2-1) for a normalized center frequency at unity.
Claim 2
Dependent Claim
201 words
A Q-invariant active filter comprising, in combination: first, second, and third amplifier means each including input means and output means; an input impedance connecting an input signal to the input means of said first amplifier means; a fIrst resistance feedback element connecting the output means of said first amplifier means to the input means of said first amplifier means; first resistive means connecting the output means of said first amplifier means to the input means of said second amplifier means; first capacitive means connecting the input means of said second amplifier means to a point of reference potential; second resistive means connecting the output means of said second amplifier means to the input means of said third amplifier means; second capacitive means connecting the input means of said third amplifier means to a point of reference potential; a second resistance feedback element connecting the output means of said third amplifier means to the input means of said first amplifier means; and wherein the product of the gain of said second and third amplifier means and the ratio of the first resistance feedback element to the second resistance feedback element is substantially equal to (4Q2-1) for a normalized center frequency at unity.
Claim 3
Dependent Claim
56 words
The combination of claim 1 wherein the time constant as determined by the product of said first resistive means and said first capacitive means and the time constant as determined by the product of said second resistive means and said second capacitive means are both substantially equal to 2Q for a normalized center frequency at unity.
Claim 4
Dependent Claim
202 words
A band-pass Q-invariant active filter comprising, in combination: first, second and third amplifier means each including input means and output means; input impedance means connecting an input signal to the input means of said first amplifier means; a first resistance feedback element connecting the output means of said first amplifier means to the input means of said first amplifier means; first capacitive means connecting the output means of said first amplifier means to the input means of said second amplifier means; first resistive means connecting the input means of said second amplifier means to a point of reference potential; second resistive means connecting the output means of said second amplifier means to the input means of said third amplifier means; second capacitive means connecting the input means of said third amplifier means to a point of reference potential; a second resistance feedback element connecting the output means of said third amplifier means to the input means of said first amplifier means; and wherein the product of the gain of said second and third amplifier means and the ratio of said first resistance feedback element to said second resistance feedback element is substantially equal to 1-(1/4Q2) for a normalized center frequency at unity.
Claim 5
Dependent Claim
202 words
A band-pass Q-invariant active filter comprising, in combination: first, second and third amplifier means each including input means and output means; input impedance means connecting an input signal to the input means of said first amplifier means; a first resistance feedback element connecting the output means of said first amplifier means to the input means of said first amplifier means; first capacitive means connecting the output means of said first amplifier means to the input means of said second amplifier means; first resistive means connecting the input means of said second amplifier means to a point of reference potential; second resistive means connecting the output means of said second amplifier means to the input means of said third amplifier means; second capacitive means connecting the input means of said third amplifier means to a point of reference potential; a second resistance feedback element connecting the output means of said third amplifier means to the input means of said first amplifier means; and wherein the product of the gain of said second and third amplifier means and the ratio of said first resistance feedback element to said second resistance feedback element is substantially equal to 1-(1/4Q2) for a normalized center frequency at unity.
Claim 6
Dependent Claim
50 words
The combination of claim 3 wherein the product of said first resistive means and said first capacitive means is a time constant substantially equal to 2Q and the product of said second resistive means and said second capacitive means is a time constant having a magnitude substantially equal to 1/2Q.
Claim 7
Dependent Claim
204 words
A bandpass Q-invariant active filter comprising, in combination: first, second and third amplifier means each including input means and output means; an input impedance connecting an input signal to the input means of said first amplifier means; a first resistance feedback element connecting the output means of said first amplifier means to the input means of said first amplifier means; first resistive means connecting the output means of said first amplifier means to the input means of said second amplifier means; first capacitive means connecting the input means of said second amplifier means to a point of reference potential; second capacitive means connecting the output means of said second amplifier means to the input means of said third amplifier means; second resistive means connecting the input means of said third amplifier means to a point of reference potential; a second resistance feedback element connecting the output means of said third amplifier means to the input means of said first amplifier means; and wherein the product of the gain of said second and third amplifier means and the ratio of the first resistance feedback element to the second resistance feedback element is substantially equal to 1 - (1/4Q2) for a normalized center frequency of unity.
Claim 8
Dependent Claim
204 words
A bandpass Q-invariant active filter comprising, in combination: first, second and third amplifier means each including input means and output means; an input impedance connecting an input signal to the input means of said first amplifier means; a first resistance feedback element connecting the output means of said first amplifier means to the input means of said first amplifier means; first resistive means connecting the output means of said first amplifier means to the input means of said second amplifier means; first capacitive means connecting the input means of said second amplifier means to a point of reference potential; second capacitive means connecting the output means of said second amplifier means to the input means of said third amplifier means; second resistive means connecting the input means of said third amplifier means to a point of reference potential; a second resistance feedback element connecting the output means of said third amplifier means to the input means of said first amplifier means; and wherein the product of the gain of said second and third amplifier means and the ratio of the first resistance feedback element to the second resistance feedback element is substantially equal to 1 - (1/4Q2) for a normalized center frequency of unity.
Claim 9
Dependent Claim
47 words
The combination of claim 5 wherein the product of the first resistive means and the first capacitive means provides a time delay substantially equal to 1/2Q and the product of the second capacitive means and the second resistive means provides a time delay substantially equal to 2Q.
Claim 10
Dependent Claim
190 words
A high pass Q-invariant active filter comprising, in combination: first, second and third amplifier means each including input means and output means; an input impedance connecting an input signal to the input means of said first amplifier means; a first resistance feedback element connecting the output means of said first amplifier means to the input means of said first amplifier means; first and second capacitive means connecting the output means of said first amplifier means to the input means of said second amplifier means and the output means of said second amplifier means to the input means of said third amplifier means, respectively; first and second resistive means connecting the input means of said second amplifier means and the input means of said third amplifier means to a point of reference potential, respectively a second resistance feedback element connecting the output means of said third amplifier means to the input means of said first amplifier means; and wherein the product of the gain of said second and third amplifier means and the ratio of said first resistance feedback element to said second resistance feedback element is substantially equal to (4Q2-1).
Claim 11
Dependent Claim
190 words
A high pass Q-invariant active filter comprising, in combination: first, second and third amplifier means each including input means and output means; an input impedance connecting an input signal to the input means of said first amplifier means; a first resistance feedback element connecting the output means of said first amplifier means to the input means of said first amplifier means; first and second capacitive means connecting the output means of said first amplifier means to the input means of said second amplifier means and the output means of said second amplifier means to the input means of said third amplifier means, respectively; first and second resistive means connecting the input means of said second amplifier means and the input means of said third amplifier means to a point of reference potential, respectively a second resistance feedback element connecting the output means of said third amplifier means to the input means of said first amplifier means; and wherein the product of the gain of said second and third amplifier means and the ratio of said first resistance feedback element to said second resistance feedback element is substantially equal to (4Q2-1).
Claim 12
Dependent Claim
60 words
The combination of claim 7 wherein a first time delay and a second time delay are determined by the product of said first resistive means and said first capacitive means and said second resistive means and said second capacitive means, respectively, with both products preselected to be substantially equal to 1/2Q when the pole center frequency is normalized at unity.
References Cited (Backward Citations)
US3296546A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-12-26 | 1976-06-26 | 1976-12-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-12-26 | 1980-06-26 | 1980-12-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-12-26 | 1984-06-26 | 1984-12-26 | $7700.00 | Window Closed / Lapsed |