Patent US3975699A successfully refreshed from Google Patents.
US3975699A
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Linear roll-off filter network
Assignee: United States Department of the Air Force
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Filing: 1975-06-19
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Granted: 1976-08-17
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Expires: 1995-06-19
Abstract
Abstract A linear filter network to provide improved distortion characteristics of a demodulated FM signal by direct synthesis of the linear amplitude transfer characteristic.
Inventors
- 👤 James B. Van Anda
- 👤 James S. Tyson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 21:46
CPC Classifications
H; H03; H03H; H03H11/00; H03H11/02; H03H11/04; H03H11/12; H03H11/1213; H04; H04N; H04N5/00; H04N5/76; H04N5/91
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
160 words
A linear filter network with a linearly decreasing amplitude versus frequency characteristic and a concurrent linear phase response comprised of a phase splitter receiving an input FM signal and providing in response thereto two output signals of equal amplitude, the first having a 90° phase and the second zero degrees, an amplifier driver receiving said first output signal, a differentiator amplifier, a variable capacitor interconnecting said driver amplifier and said differentiator amplifier, the gain of said differentiator amplifier being set by the adjustment of said variable capacitor thereby selecting a preselected null frequency of said linear filter network, means to delay said second output signal a predetermined time exactly equal to the propagation delay of said driver amplifier and differentiator amplifier in combination so as to restore the phase relationship of said two output signals, and means to vectorally sum the delayed signal and the differentiated signal to provide a resultant signal having a linear function with respect to frequency.
Claim 2
Dependent Claim
160 words
A linear filter network with a linearly decreasing amplitude versus frequency characteristic and a concurrent linear phase response comprised of a phase splitter receiving an input FM signal and providing in response thereto two output signals of equal amplitude, the first having a 90° phase and the second zero degrees, an amplifier driver receiving said first output signal, a differentiator amplifier, a variable capacitor interconnecting said driver amplifier and said differentiator amplifier, the gain of said differentiator amplifier being set by the adjustment of said variable capacitor thereby selecting a preselected null frequency of said linear filter network, means to delay said second output signal a predetermined time exactly equal to the propagation delay of said driver amplifier and differentiator amplifier in combination so as to restore the phase relationship of said two output signals, and means to vectorally sum the delayed signal and the differentiated signal to provide a resultant signal having a linear function with respect to frequency.
Claim 3
Dependent Claim
21 words
A linear filter network as described in claim 1 wherein said means to sum vectorally is comprised of a hybrid coupler.
Claim 4
Dependent Claim
32 words
A linear filter network as described in claim 2 further including an emitter follower having unity gain and connected to the input of said hybrid quadrature splitter operating as a driver therefor.
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) | 1979-08-17 | 1980-02-16 | 1980-08-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-08-17 | 1984-02-16 | 1984-08-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-08-17 | 1988-02-16 | 1988-08-17 | $7700.00 | Window Closed / Lapsed |