US3793593A
Expired / Lapsed
US
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Frequency selective network
Assignee: Westinghouse Electric Corp
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Filing: 1971-08-18
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Granted: 1974-02-19
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Expires: 1991-08-18
Abstract
Abstract A frequency selective network employing negative and positive feedback in conjunction with an inductorless bandpass or reject filter to provide a stable bandpass or reject characteristic. Sole adjustment of the negative feedback gain varies the center frequency of the filter over a wide frequency range without appreciably affecting the bandwidth. An all electronic frequency selective network is achieved by providing a voltage controlled variable gain stage as the means of adjusting the feedback gain.
Inventors
- 👤 P Kennedy
- 👤 G Sziklai
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 15:30
CPC Classifications
H; H03; H03H; H03H11/00; H03H11/02; H03H11/04; H03H11/12; H03H11/1295
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
116 words
A tunable frequency selective network operative with a signal input, comprising: an amplifier responsive to said signal input for providing an output; first and second negative feedback means responsive to said output of said amplifier, said first negative feedback means providing a constant gain feedback voltage and said second negative feedback means including means to vary the feedback gain providing a second negative feedback voltage adjustable relative to said first negative feedback voltage; and filter means responsive to said first and second negative feedback voltages so that the center frequency of said filter means varies as said second negative feedback voltage is varied and for providing an input to said amplifier completing the negative feedback path.
Claim 2
Dependent Claim
116 words
A tunable frequency selective network operative with a signal input, comprising: an amplifier responsive to said signal input for providing an output; first and second negative feedback means responsive to said output of said amplifier, said first negative feedback means providing a constant gain feedback voltage and said second negative feedback means including means to vary the feedback gain providing a second negative feedback voltage adjustable relative to said first negative feedback voltage; and filter means responsive to said first and second negative feedback voltages so that the center frequency of said filter means varies as said second negative feedback voltage is varied and for providing an input to said amplifier completing the negative feedback path.
Claim 3
Dependent Claim
31 words
A tunable frequency selective network as recited in claim 1, wherein: said signal input is a current source having a high output impedance so that selectivity of said network is enhanced.
Claim 4
Dependent Claim
58 words
A tunable selective frequency network as recited in claim 1, wherein: said means to vary the feedback gain of said second feedback means includes a transistor for providing an output to said filter means and a potentiometer connected to the input of said transistor so that said output of said transistor is varied by adjustment of said potentiometer.
Claim 5
Dependent Claim
62 words
A tunable selective frequency network as recited in claim 1, wherein: said means to vary the feedback of said second feedback means includes a transistor for providing an output and a voltage controlled variable gain stage connected to the input of said transistor so that said output of said transistor is varied by adjustment of the gain of said variable gain stage.
Claim 6
Dependent Claim
68 words
A tunable frequency selective network as recited in claim 1, wherein; said filter means comprises a first branch including a pair of series capacitors and a resistor connecting the junction of said pair of capacitors to said output of said amplifier, a second branch including a pair of series resistors and a capacitor connecting the junction of said pair of resistors also to said output of said amplifier.
Claim 7
Dependent Claim
62 words
A tunable selective frequency network as recited in claim 5, wherein: said output of said first negative feedback means is applied to said first branch; and said output of said second negative feedback means is applied to said second branch so that bandwidth and amplitude response at resonance of said tunable selective frequency network remain constant as the center frequency is varied.
Claim 8
Dependent Claim
59 words
A tunable selective frequeNcy network as recited in claim 5, wherein: said output of said first negative feedback means is applied to said second branch; and said output of said second negative feedback means is applied to said first branch so that d.c. bias of said amplifier remains constant during adjustment of center frequency of said frequency selective network.
Claim 9
Dependent Claim
25 words
A tunable frequency selective network as recited in claim 5, wherein: said network further includes a first output taken at said output of said amplifier.
Claim 10
Dependent Claim
44 words
A tunable frequency selective network as recited in claim 5, wherein: said filter means further includes a second output at said junction of said capacitors of said first branch for developing a utilization signal having a frequency bandpass characteristic represented by the transfer function:
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) | 1977-02-18 | 1977-08-20 | 1978-02-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-02-18 | 1981-08-20 | 1982-02-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-02-18 | 1985-08-20 | 1986-02-19 | $7700.00 | Window Closed / Lapsed |