Patent US3609567A successfully refreshed from Google Patents.
US3609567A
Expired / Lapsed
US
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Rc networks and amplifiers employing the same
Assignee: National Aeronautics and Space Administration
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Filing: 1970-04-17
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Granted: 1971-09-28
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Expires: 1990-04-17
Abstract
Abstract The active filter circuit of the present invention comprises a passive RC network and a DC voltage or operational amplifier. The resistive and capacitive elements of the passive RC network determine the location of a pair of complex conjugate zeros along the j omega axis. Connected to the RC network in shunt are a load resistor and a load capacitor. A feedback network interconnects the output of the voltage amplifier with the passive RC network. By regulating the value of the load resistor and the value of the load capacitor jointly or severally, the location of a pair of complex conjugate poles produced by the active filter can be adjusted separately and independently from the zeros. In addition thereto, the regulation of the gain of the DC voltage or operational amplifier or the changing of the feedback voltage of the DC voltage or operational amplifier adjusts independently the location of the pair of complex conjugate poles relative to the zeros. When a plurality of active filter circuits are connected in cascade, a frequency-selective amplifier is formed with the DC voltage or operational amplifiers serving additionally as isolation devices between successive active filter circuits. It is to be observed that each active filter circuit produces real frequency zeros of transmission at any desired frequency independently of the location of complex poles with respect to the zeros.
Inventors
- 👤 William J Kerwin
- 👤 Lawrence P Huelsman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 09:14
CPC Classifications
H; H03; H03F; H03F3/00; H03F3/45; H03F3/45071; H03H; H03H11/00; H03H11/02; H03H11/04; H03H11/12; H03H11/126
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
109 words
A second-order active RC filter with a transfer function permitting the poles to be positioned independently of the zeros comprising an inductanceless impedance, a passive RC network having an input for receiving signals to be filtered and an output connected to said impedance, a noninverting voltage amplifier for amplifying the voltage across said impedance, said amplifier having an output, a feedback path connected between said amplifier output and said RC network, said zeros of said filter being on the j omega axis of the p-plane, the magnitude of said impedance and the gain of said amplifier determining the placement of said poles independently of the locatiOn of said zeros.
Claim 2
Dependent Claim
109 words
A second-order active RC filter with a transfer function permitting the poles to be positioned independently of the zeros comprising an inductanceless impedance, a passive RC network having an input for receiving signals to be filtered and an output connected to said impedance, a noninverting voltage amplifier for amplifying the voltage across said impedance, said amplifier having an output, a feedback path connected between said amplifier output and said RC network, said zeros of said filter being on the j omega axis of the p-plane, the magnitude of said impedance and the gain of said amplifier determining the placement of said poles independently of the locatiOn of said zeros.
Claim 3
Dependent Claim
28 words
Apparatus as defined in claim 1 wherein the radial distance of said poles from the origin of said p-plane is a function of said magnitude of said impedance.
Claim 4
Dependent Claim
28 words
Apparatus as defined in claim 1 wherein the angular position of said poles with respect to the origin of said p-plane is a function of said amplifier gain.
Claim 5
Dependent Claim
39 words
Apparatus as defined in claim 1 wherein the passive RC network comprises first and second T-networks, said first network having two capacitive arms and a resistive leg, and said second T-network having two resistive arms and a capacitive leg.
Claim 6
Dependent Claim
131 words
A second-order active RC filter with a transfer function permitting the poles to be positioned independently of the zeros comprising first and second input terminals, first and second output terminals, said second input terminal being connected to said second output terminal, a noninverting voltage amplifier having an input and an output, said amplifier output being connected to said first output terminal, a four-terminal passive RC network, said terminals of said network being connected to said first input terminal, said second input terminal, said amplifier input, and said amplifier output, respectively, an inductanceless impedance connected between said amplifier input and said second output terminal, the magnitude of said impedance and the gain of said amplifier determining the placement of said poles of transmission independently of the location of the zeros of transmission.
Claim 7
Dependent Claim
131 words
A second-order active RC filter with a transfer function permitting the poles to be positioned independently of the zeros comprising first and second input terminals, first and second output terminals, said second input terminal being connected to said second output terminal, a noninverting voltage amplifier having an input and an output, said amplifier output being connected to said first output terminal, a four-terminal passive RC network, said terminals of said network being connected to said first input terminal, said second input terminal, said amplifier input, and said amplifier output, respectively, an inductanceless impedance connected between said amplifier input and said second output terminal, the magnitude of said impedance and the gain of said amplifier determining the placement of said poles of transmission independently of the location of the zeros of transmission.
Claim 8
Dependent Claim
25 words
Apparatus as defined in claim 5 wherein said passive RC network has a given rejection frequency and the overall transfer function of said filter is
Claim 9
Dependent Claim
136 words
A second-order active RC network with a transfer function permitting the poles to be positioned independently of the zeros comprising first and second input terminals, first and second output terminals, said second input terminal being connected to said second output terminal, a noninverting voltage amplifier having an input and an output, said amplifier output being connected to said first output terminal, a first three-terminal T-network comprised of resistors and capacitors, said three terminals being connected to said first input terminal, said second input terminal and said amplifier input, respectively, a second three-terminal T-network comprised of resistors and capacitors, said three terminals of said second T-network being connected to said first input terminal, said amplifier input terminal and said amplifier output terminal, respectively, and an inductanceless impedance connected between said amplifier input and said second output terminal.
Claim 10
Dependent Claim
136 words
A second-order active RC network with a transfer function permitting the poles to be positioned independently of the zeros comprising first and second input terminals, first and second output terminals, said second input terminal being connected to said second output terminal, a noninverting voltage amplifier having an input and an output, said amplifier output being connected to said first output terminal, a first three-terminal T-network comprised of resistors and capacitors, said three terminals being connected to said first input terminal, said second input terminal and said amplifier input, respectively, a second three-terminal T-network comprised of resistors and capacitors, said three terminals of said second T-network being connected to said first input terminal, said amplifier input terminal and said amplifier output terminal, respectively, and an inductanceless impedance connected between said amplifier input and said second output terminal.
Claim 11
Dependent Claim
30 words
Apparatus as defined in claim 7 wherein said first T-network has two resistive arms and a capacitive leg, and said second T-network has two capacitive arms and a resistive leg.
Claim 12
Dependent Claim
30 words
Apparatus as defined in claim 7 wherein said first T-network has two capacitive arms and a resistive leg, and said second T-network has two resistive arms and a capacitive leg.
Claim 13
Dependent Claim
158 words
A second-order active RC filter with a transfer function enabling the poles of transmission to be located in the left-half of the p-plane independently of the zeros of transmission comprising first and second input terminals, a noninverting voltage amplifier having an input and an output, first and second output terminals, said output of said amplifier being connected to said first output terminal, said second input terminal being connected to said second output terminal, first and second resistors connected in series between said first input terminal and said amplifier input, first and second capacitors connected in series with each other and connected in shunt with said first and second resistors, a third capacitor connected between said node of said first and second resistors and said second input terminal, a third resistor connected between said amplifier output and the node of said first and second capacitors, and an inductanceless impedance connected between said amplifier Input and said second output terminal.
Claim 14
Dependent Claim
158 words
A second-order active RC filter with a transfer function enabling the poles of transmission to be located in the left-half of the p-plane independently of the zeros of transmission comprising first and second input terminals, a noninverting voltage amplifier having an input and an output, first and second output terminals, said output of said amplifier being connected to said first output terminal, said second input terminal being connected to said second output terminal, first and second resistors connected in series between said first input terminal and said amplifier input, first and second capacitors connected in series with each other and connected in shunt with said first and second resistors, a third capacitor connected between said node of said first and second resistors and said second input terminal, a third resistor connected between said amplifier output and the node of said first and second capacitors, and an inductanceless impedance connected between said amplifier Input and said second output terminal.
Claim 15
Dependent Claim
34 words
An active RC filter as defined in claim 10 wherein the magnitude of said impedance and the gain of said amplifier determines the placement of said poles independently of the location of said poles.
Claim 16
Dependent Claim
31 words
An active RC filter as defined in claim 11 wherein the radial distance of said poles from the origin of the p-plane is a function of said magnitude of said impedance.
Claim 17
Dependent Claim
31 words
An active RC filter as defined in claim 11 wherein the angular position of the poles with respect to the origin of the p-plane is a function of said amplifier gain.
Claim 18
Dependent Claim
29 words
An active RC filter as defined in claim 10 wherein each of said resistors is replaced with a capacitor, and each of said capacitors is replaced with a resistor.
Claim 19
Dependent Claim
34 words
An active RC filter as defined in claim 14 wherein the magnitude of said impedance and the gain of said amplifier determines the placement of said poles independently of the location of said poles.
Claim 20
Dependent Claim
31 words
An active RC filter as defined in claim 15 wherein the radial distance of said poles from the origin of the p-plane is a function of said magnitude of said impedance.
Claim 21
Dependent Claim
31 words
An active RC filter as defined in claim 15 wherein the angular position of the poles with respect to the origin of the p-plane is a function of said amplifier gain.
Claim 22
Dependent Claim
130 words
An active RC filter comprising first and second input terminals, a noninverting amplifier having an input and an output, first and second resistors connected in series between said first input terminal and said amplifier input, a first capacitor connected between said first and second resistors and said second input terminal, second and third capacitors connected in series between said first input terminal and said amplifier input, first and second output terminals, said first output terminal being connected to said amplifier output, said second input terminal being in common with said second output terminal, a third resistor being connected between said second and third capacitors and said amplifier output, a fourth resistor connected between said amplifier input and said second output terminal, said resistors and amplifiers having the following normalized values:
Claim 23
Dependent Claim
130 words
An active RC filter comprising first and second input terminals, a noninverting amplifier having an input and an output, first and second resistors connected in series between said first input terminal and said amplifier input, a first capacitor connected between said first and second resistors and said second input terminal, second and third capacitors connected in series between said first input terminal and said amplifier input, first and second output terminals, said first output terminal being connected to said amplifier output, said second input terminal being in common with said second output terminal, a third resistor being connected between said second and third capacitors and said amplifier output, a fourth resistor connected between said amplifier input and said second output terminal, said resistors and amplifiers having the following normalized values:
Claim 24
Dependent Claim
143 words
An active RC filter comprising a noninverting amplifier having an input and an output, a first and second input terminal, first and second resistors connected in series between said first input terminal and said amplifier input, a first capacitor connected between said node of said first and second resistors and said second input terminal, second and third capacitors connected in series and jointly connected in shunt with said first and second resistors, first and second output terminals, said amplifier output being connected to said first output terminal, said second input terminal being in common with said second output terminal, a third resistor being connected between said junction of said second and third capacitors and said output of said amplifier, a fourth capacitor connected between said input of said amplifier and said second output terminal, said resistors and capacitors having the following normalized values:
Claim 25
Dependent Claim
143 words
An active RC filter comprising a noninverting amplifier having an input and an output, a first and second input terminal, first and second resistors connected in series between said first input terminal and said amplifier input, a first capacitor connected between said node of said first and second resistors and said second input terminal, second and third capacitors connected in series and jointly connected in shunt with said first and second resistors, first and second output terminals, said amplifier output being connected to said first output terminal, said second input terminal being in common with said second output terminal, a third resistor being connected between said junction of said second and third capacitors and said output of said amplifier, a fourth capacitor connected between said input of said amplifier and said second output terminal, said resistors and capacitors having the following normalized values:
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-09-27 | 1975-03-29 | 1975-09-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-09-27 | 1979-03-29 | 1979-09-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-09-27 | 1983-03-29 | 1983-09-28 | $7700.00 | Window Closed / Lapsed |