US3924199A
Expired / Lapsed
US
⏱️ 0.0 years remaining
N-pole filter circuit having cascaded filter sections
Assignee: Fender Musical Instruments Corp
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Filing: 1974-02-04
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Granted: 1975-12-02
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Expires: 1994-02-04
Abstract
Abstract The n-pole filter preferably has four filter circuits cascaded in series. Each of the filter circuits is preferably a low-pass filter circuit and each has a controllable frequency response which is variably controlled from a common current or voltage source. Each filter circuit includes a transconductance circuit and inverting operational amplifier. A feedback resistor couples between the first and last filter circuits and is adjustable to provide different amounts of resonance.
Inventors
- 👤 Alan R Pearlman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 23:13
CPC Classifications
H; H03; H03H; H03H11/00; H03H11/02; H03H11/04; H03H11/12; H03H11/1291; H03F; H03F3/00; H03F3/45; H03F3/45071; H03G; H03G5/00
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
119 words
An active low-pass filter having a selectable cutoff frequency and providing a controllable resonance peak in the vicinity thereof, comprising A. n low-pass series-connected filter sections, each having an input and an output and characterized by a cutoff frequency selected by a control current applied thereto, each contributing a phrase shaft of 180/n degrees at resonance, B. a current source responsive to control input applied thereto to provide a substantially identical control current to each filter section for selecting the cutoff frequency thereof, in accordance with said control input, and C. a resistor interconnecting the output of a last of said filter with the input of a first thereof and adjustable to vary the resonance peak of the filter.
Claim 2
Dependent Claim
119 words
An active low-pass filter having a selectable cutoff frequency and providing a controllable resonance peak in the vicinity thereof, comprising A. n low-pass series-connected filter sections, each having an input and an output and characterized by a cutoff frequency selected by a control current applied thereto, each contributing a phrase shaft of 180/n degrees at resonance, B. a current source responsive to control input applied thereto to provide a substantially identical control current to each filter section for selecting the cutoff frequency thereof, in accordance with said control input, and C. a resistor interconnecting the output of a last of said filter with the input of a first thereof and adjustable to vary the resonance peak of the filter.
Claim 3
Dependent Claim
11 words
A filter according to claim 1 in which n equals 4.
Claim 4
Dependent Claim
18 words
A filter according to claim 2 which includes a plurality of resistors interconnecting corresponding pairs of filter sections.
Claim 5
Dependent Claim
23 words
A filter according to claim 2 in which each filter section comprises an integrator and a variable conductance means forming a part thereof.
Claim 6
Dependent Claim
31 words
A filter according to claim 2 which includes a voltage to current converter for converting a control voltage to a corresponding current for supplying the control input to said current source.
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) | 1978-12-01 | 1979-06-02 | 1979-12-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-12-01 | 1983-06-02 | 1983-12-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-12-01 | 1987-06-02 | 1987-12-02 | $7700.00 | Window Closed / Lapsed |