US3946328A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Functionally tunable active filter
Assignee: Nortel Networks Ltd
•
Filing: 1975-01-27
•
Granted: 1976-03-23
•
Expires: 1995-01-27
Abstract
Abstract A family of RC active filters in which band-pass, low-pass notch, high-pass notch, band-stop and all-pass second order sections may be realized. The filters provide unidirectional functional tuning of the four basic parameters ω o , Q o , ω z and Q z through resistive trimming.
Inventors
- 👤 Stalin A. Boctor
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 03:34
CPC Classifications
H; H03; H03H; H03H11/00; H03H11/02; H03H11/04; H03H11/12; H03H11/126
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
170 words
An RC functionally tunable active filter comprising: input, output and common terminals; a differential amplifier having inverting and noninverting inputs, and an output connected to the output terminal; a first capacitor and a first resistor serially connected between the input terminal and the inverting input of the differential amplifier; a second capacitor connected between the inverting input and the output of the differential amplifier; a second resistor connected between the junction of the first capacitor and resistor, and the common terminal; a third resistor connected between said junction and the output of the differential amplifier; and conductive means connected between the noninverting input of the differential amplifier and the common terminal; the differential amplifier, resistors, capacitors and conductive means coacting such that variations in resistance of the first and/or third resistors affect the pole resonant frequency ω o , and variations in resistance of the second resistor affect the pole quality factor Q o but not ω o , thereby enabling a unidirectional sequence of functional tuning of the filter.
Claim 2
Dependent Claim
170 words
An RC functionally tunable active filter comprising: input, output and common terminals; a differential amplifier having inverting and noninverting inputs, and an output connected to the output terminal; a first capacitor and a first resistor serially connected between the input terminal and the inverting input of the differential amplifier; a second capacitor connected between the inverting input and the output of the differential amplifier; a second resistor connected between the junction of the first capacitor and resistor, and the common terminal; a third resistor connected between said junction and the output of the differential amplifier; and conductive means connected between the noninverting input of the differential amplifier and the common terminal; the differential amplifier, resistors, capacitors and conductive means coacting such that variations in resistance of the first and/or third resistors affect the pole resonant frequency ω o , and variations in resistance of the second resistor affect the pole quality factor Q o but not ω o , thereby enabling a unidirectional sequence of functional tuning of the filter.
Claim 3
Dependent Claim
44 words
An RC functionally tunable active filter as defined in claim 1 in which the conductive means is a direct connection between the noninverting input of the differential amplifier and the common terminal; and the differential amplifier, resistors and capacitors coact as a band-pass filter.
Claim 4
Dependent Claim
145 words
An RC functionally tunable active filter as defined in claim 1 in which: the conductive means comprises a fourth resistor connected between the noninverting input of the differential amplifier and the common terminal; and which additionally comprises: a fifth resistor connected between the noninverting input of the differential amplifier and the input terminal; and a sixth resistor connected between the inverting input of the differential amplifier and the common terminal; the differential amplifier, resistors and capacitors coacting as a low-pass notch filter such that variations in resistance of the sixth resistor affect the zero resonant frequency ω z but not ω o and Q o , and variations in resistance of the fourth and/or fifth resistors affect the zero quality factor Q z but not ω o , ω z and Q o , thereby enabling a unidirectional sequence of functional tuning of the filter.
Claim 5
Dependent Claim
159 words
An RC functionally tunable active filter as defined in claim 1 in which: the conductive means comprises a fourth resistor connected between the noninverting input of the differential amplifier and the common terminal; and which additionally comprises: a fifth resistor connected between the noninverting input of the differential amplifier and the input terminal; and a sixth resistor and a third capacitor connected in shunt between the inverting input of the differential amplifier and the common terminal; the differential amplifier, resistors and capacitors coacting as either a high-pass notch filter, a band-stop filter or an all-pass filter such that variations in resistance of the sixth resistor affect the zero resonant frequency ω z but not ω o and Q o , and variations in resistance of the fourth and/or fifth resistors affect the zero quality factor Q z but not ω o , ω z and Q o , thereby enabling a unidirectional sequence of functional tuning of the filter.
Claim 6
Dependent Claim
182 words
An RC functionally tunable active filter comprising: input, output and common terminals; a differential amplifier having inverting and noninverting inputs, and an output connected to the output terminal of the filter; a first capacitor and a first resistor serially connected between the input terminal and the inverting input of the differential amplifier; a second capacitor connected between the inverting input and the output of the differential amplifier; a second resistor connected between the junction of the first capacitor and resistor, and the common terminal; a third resistor connected between said junction and the output of the differential amplifier; and the noninverting input of the differential amplifier being connected to the common terminal; the differential amplifier, resistors and capacitors coacting such that variations of the resistance of the first and/or third resistors affect the pole resonant frequency ω o , and variations in resistance of the second resistor affect the pole quality factor Q o but not ω o ; and the values of the resistors and capacitors are such that: ω z = 0, whereby the filter functions as a band-pass filter.
Claim 7
Dependent Claim
182 words
An RC functionally tunable active filter comprising: input, output and common terminals; a differential amplifier having inverting and noninverting inputs, and an output connected to the output terminal of the filter; a first capacitor and a first resistor serially connected between the input terminal and the inverting input of the differential amplifier; a second capacitor connected between the inverting input and the output of the differential amplifier; a second resistor connected between the junction of the first capacitor and resistor, and the common terminal; a third resistor connected between said junction and the output of the differential amplifier; and the noninverting input of the differential amplifier being connected to the common terminal; the differential amplifier, resistors and capacitors coacting such that variations of the resistance of the first and/or third resistors affect the pole resonant frequency ω o , and variations in resistance of the second resistor affect the pole quality factor Q o but not ω o ; and the values of the resistors and capacitors are such that: ω z = 0, whereby the filter functions as a band-pass filter.
Claim 8
Dependent Claim
274 words
An RC functionally tunable active filter comprising: input, output and common terminals; a differential amplifier having inverting and noninverting inputs, and an output connected to the output terminal of the filter; a first capacitor and a first resistor serially connected between the input terminal and the inverting input of the differential amplifier; a second capacitor connected between the inverting input and the output of the dfferential amplifier; a second resistor connected between the junction of the first capacitor and resistor, and the common terminal; a third resistor connected between said junction and the output of the differential amplifier; a fourth resistor connected between the noninverting input of the differential amplifier and the common terminal; a fifth resistor connected between the input terminal and the noninverting input of the differential amplifier; and a sixth resistor connected between the inverting input of the differential amplifier and the common terminal; the differential amplifier, resistors and capacitors coacting such that variations in the resistance of the first and/or third resistors affect the pole resonant frequency ω o , variations in resistance of the second resistor affect the pole quality factor Q o but not ω o , variations in resistance of the sixth resistor affect the zero resonant frequency ω z but not ω o and Q o , and variations in resistance of the fourth and/or fifth resistors affect the zero quality factor Q z but not ω o , ω z and Q o ; and the values of the resistors and capacitors are such that: ω z > ω o , and Q z = ∞, whereby the filter functions as a low-pass notch filter.
Claim 9
Dependent Claim
274 words
An RC functionally tunable active filter comprising: input, output and common terminals; a differential amplifier having inverting and noninverting inputs, and an output connected to the output terminal of the filter; a first capacitor and a first resistor serially connected between the input terminal and the inverting input of the differential amplifier; a second capacitor connected between the inverting input and the output of the dfferential amplifier; a second resistor connected between the junction of the first capacitor and resistor, and the common terminal; a third resistor connected between said junction and the output of the differential amplifier; a fourth resistor connected between the noninverting input of the differential amplifier and the common terminal; a fifth resistor connected between the input terminal and the noninverting input of the differential amplifier; and a sixth resistor connected between the inverting input of the differential amplifier and the common terminal; the differential amplifier, resistors and capacitors coacting such that variations in the resistance of the first and/or third resistors affect the pole resonant frequency ω o , variations in resistance of the second resistor affect the pole quality factor Q o but not ω o , variations in resistance of the sixth resistor affect the zero resonant frequency ω z but not ω o and Q o , and variations in resistance of the fourth and/or fifth resistors affect the zero quality factor Q z but not ω o , ω z and Q o ; and the values of the resistors and capacitors are such that: ω z > ω o , and Q z = ∞, whereby the filter functions as a low-pass notch filter.
Claim 10
Dependent Claim
249 words
An RC functionally tunable active filter comprising: input, output and common terminals; a differential amplifier having inverting and noninverting inputs, and an output connected to the output terminal of the filter; a first capacitor and a first resistor serially connected between the input terminal and the inverting input of the differential amplifier; a second capacitor connected between the inverting input and the output of the differential amplifier; a second resistor connected between the junction of the first capacitor and resistor, and the common terminal; a third resistor connected between said junction and the output of the differential amplifier; a fourth resistor connected between the noninverting input of the differential amplifier and the common terminal; a fifth resistor connected between the input terminal and the noninverting input of the differential amplifier; and a sixth resistor and a third capacitor connected in shunt between the inverting input of the differential amplifier and the common terminal; the differential amplifier, resistors and capacitors coacting such that variations in the resistance of the first and/or third resistors affect the pole resonant frequency ω o , variations in resistance of the second resistor affect the pole quality factor Q o but not ω o , variations in resistance of the sixth resistor affect the zero resonant frequency ω z but not ω o and Q o , and variations in resistance of the fourth and/or fifth resistors affect the zero quality factor Q z but not ω o , ω z and Q o .
Claim 11
Dependent Claim
249 words
An RC functionally tunable active filter comprising: input, output and common terminals; a differential amplifier having inverting and noninverting inputs, and an output connected to the output terminal of the filter; a first capacitor and a first resistor serially connected between the input terminal and the inverting input of the differential amplifier; a second capacitor connected between the inverting input and the output of the differential amplifier; a second resistor connected between the junction of the first capacitor and resistor, and the common terminal; a third resistor connected between said junction and the output of the differential amplifier; a fourth resistor connected between the noninverting input of the differential amplifier and the common terminal; a fifth resistor connected between the input terminal and the noninverting input of the differential amplifier; and a sixth resistor and a third capacitor connected in shunt between the inverting input of the differential amplifier and the common terminal; the differential amplifier, resistors and capacitors coacting such that variations in the resistance of the first and/or third resistors affect the pole resonant frequency ω o , variations in resistance of the second resistor affect the pole quality factor Q o but not ω o , variations in resistance of the sixth resistor affect the zero resonant frequency ω z but not ω o and Q o , and variations in resistance of the fourth and/or fifth resistors affect the zero quality factor Q z but not ω o , ω z and Q o .
Claim 12
Dependent Claim
43 words
An RC functionally tunable active filter as defined in claim 7 in which the values of the resistors and capacitors are such that: ω z < ω o , and Q z = ∞, whereby the filter functions as a high-pass notch filter.
Claim 13
Dependent Claim
44 words
An RC functionally tunable active filter as defined in claim 7 in which: the values of the resistors and capacitors are such that: ω z = ω o , and Q z = -Q o , whereby the filter functions as an all-pass filter.
Claim 14
Dependent Claim
42 words
An RC functionally tunable active filter as defined in claim 7 in which the values of the resistors and capacitors are such that: ω z = ω o , and Q z = ∞, whereby the filter functions as a band-stop filter.
References Cited (Backward Citations)
US3838351A
Cited
US3805178A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-03-23 | 1979-09-22 | 1980-03-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-03-23 | 1983-09-22 | 1984-03-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-03-23 | 1987-09-22 | 1988-03-23 | $7700.00 | Window Closed / Lapsed |