Patent US4185250A successfully refreshed from Google Patents.
US4185250A
Expired / Lapsed
US
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Voice frequency RC active filter
Assignee: Wescom Switching Inc
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Filing: 1978-05-03
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Granted: 1980-01-22
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Expires: 1998-05-03
Abstract
Abstract A voice-frequency RC-active filter comprising a plurality of resistors and generalized impedance converter networks for synthesizing the frequency response of a preselected LC filter. Each generalized impedance converter network includes a pair of operational amplifiers and a plurality of impedances Z1, Z2, Z3, Z4 and Z5 interconnected with the amplifiers to provide the network with a driving point impedance ##EQU1## in which at least one of the impedances in both the numerator and the denominator of Zi includes a film-type resistor. At least one of the film-type resistors included in the impedances Z1, Z2, Z3, Z4 and Z5 is functionally trimmed to tune the filter. The capacitors in the filter are preferably discrete polycarbonate capacitors with a capacitance tolerance of ±5%, and all having the same value.
Inventors
- 👤 John F. Regan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 13:35
CPC Classifications
H; H03; H03H; H03H11/00; H03H11/02; H03H11/04; H03H11/12; H03H11/0416; H03H11/40
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
105 words
A voice-frequency RC-active filter comprising a plurality of resistors and generalized impedance converter networks for synthesizing the frequency response of a preselected LC filter, each generalized impedance converter network including a pair of operational amplifiers and a plurality of impedances Z1, Z2, Z3, Z4 and Z5 interconnected with said amplifiers to provide the network with a driving point impedance ##EQU5## in which at least one of the impedances in both the numerator and the denominator of Zi includes a film-type resistor, at least one of the film-type resistors included in the impedances Z1, Z2, Z3, Z4 and Z5 being functionally trimmed to tune the filter.
Claim 2
Dependent Claim
105 words
A voice-frequency RC-active filter comprising a plurality of resistors and generalized impedance converter networks for synthesizing the frequency response of a preselected LC filter, each generalized impedance converter network including a pair of operational amplifiers and a plurality of impedances Z1, Z2, Z3, Z4 and Z5 interconnected with said amplifiers to provide the network with a driving point impedance ##EQU5## in which at least one of the impedances in both the numerator and the denominator of Zi includes a film-type resistor, at least one of the film-type resistors included in the impedances Z1, Z2, Z3, Z4 and Z5 being functionally trimmed to tune the filter.
Claim 3
Dependent Claim
25 words
A voice-frequency RC-active filter as set forth in claim 1 wherein said filter includes a plurality of capacitors all of which have the same value.
Claim 4
Dependent Claim
23 words
A voice-frequency RC-active filter as set forth in claim 2 wherein said capacitors are discrete polycarbonate capacitors with a capacitance tolerance of ±5%.
Claim 5
Dependent Claim
24 words
A voice-frequency RC-active filter as set forth in claim 1 which includes a plurality of said generalized impedance converter networks in a ladder network.
Claim 6
Dependent Claim
41 words
A voice-frequency RC-active filter as set forth in claim 1 wherein each generalized impedance converter network comprises a frequency dependent negative resistance network that includes a plurality of capacitors and film-type resistors comprising said impedances Z1, Z2, Z3, Z4 and Z5.
Claim 7
Dependent Claim
48 words
A voice-frequency RC-active filter as set forth in claim 1 wherein each inductor L in said preselected LC filter is represented by a resistor in said RC-active filter, and each capacitor in said preselected LC filter is represented by a generalized impedance converter network in said RC-active filter.
Claim 8
Dependent Claim
78 words
A voice-frequency RC-active filter as set forth in claim 1 wherein at least one capacitor is interconnected with said resistors and generalized impedance converter networks to synthesize the frequency response of a preselected LCR filter, and an operational amplifier is connected to said capacitor with at least one auxiliary film-type resistor for adjusting the gain of said amplifier and thereby adjusting the effective value of said capacitor, said auxiliary film-type resistor being functionally trimmed to tune the filter.
Claim 9
Independent Claim
119 words
A method of producing a voice-frequency RC-active filter to meet a predetermined passband ripple specification, said method comprising: interconnecting a plurality of resistors and generalized impedance converter networks for synthesizing the frequency response of a preselected LC filter, each generalized impedance converting network including a pair of operational amplifiers and a plurality of impedances Z1, Z2, Z3, Z4 and Z5 interconnected with said amplifiers to provide the network with a driving point impedance ##EQU6## in which at least one of the impedances in both the numerator and the denominator of Zi includes a film-type resistor, and tuning said filter by functionally trimming at least one of the film-type resistors included in the impedance Z1, Z2, Z3, Z4 and Z5.
Claim 10
Independent Claim
119 words
A method of producing a voice-frequency RC-active filter to meet a predetermined passband ripple specification, said method comprising: interconnecting a plurality of resistors and generalized impedance converter networks for synthesizing the frequency response of a preselected LC filter, each generalized impedance converting network including a pair of operational amplifiers and a plurality of impedances Z1, Z2, Z3, Z4 and Z5 interconnected with said amplifiers to provide the network with a driving point impedance ##EQU6## in which at least one of the impedances in both the numerator and the denominator of Zi includes a film-type resistor, and tuning said filter by functionally trimming at least one of the film-type resistors included in the impedance Z1, Z2, Z3, Z4 and Z5.
Claim 11
Dependent Claim
82 words
A method of producing a voice-frequency RC-active filter as set forth in claim 8 wherein at least one capacitor is interconnected with said resistors and generalized impedance converter networks to sythesize the frequency response of a preselected LCR filter, an operational amplifier is connected to said capacitor with at least one auxiliary film-type resistor for adjusting the gain of said amplifier and thereby adjusting the effective value of said capacitor, and said auxiliary film-type resistor is functionally trimmed to tune said filter.
References Cited (Backward Citations)
US2983875A
Cited
GB1413722A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1983-01-21 | 1983-07-23 | 1984-01-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-01-21 | 1987-07-23 | 1988-01-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-01-21 | 1991-07-23 | 1992-01-22 | $7700.00 | Window Closed / Lapsed |