US4348692A
Expired / Lapsed
US
⏱️ 0.0 years remaining
VTR With equalizer
Assignee: Emtec Magnetics GmbH
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Filing: 1980-03-13
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Granted: 1982-09-07
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Expires: 2000-03-13
Abstract
Abstract Equalizer circuitry for a wideband signal recording/playback system, in particular a home video system, comprises a pre-emphasis and a de-emphasis circuit in the recording channel and the playback channel respectively. In an advantageous embodiment, the pre-emphasis and de-emphasis circuits are of the second-order type. In the preferred embodiment of the circuitry, in each of said channels there is provided a circuit for group-delay equalization, preferably an all-pass filter which comprises at least one substantially symmetrical transistor stage provided with a bridge circuit consisting of at least one reactive impedance and ohmic resistance and located between emitter and collector. Practical embodiments of the bridge circuit comprise several series-connected parallel LC sections and one ohmic resistance. Advantageously, conventional filter stages in the channels may be at least partially included in said circuit for group-delay equalization. Conventional delay means provided in color video systems for equalization of the delay between color and video signals can therefore be integrated in said circuit for group-delay equlization.
Inventors
- 👤 Andreas Ilmer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 01:04
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/76; H04N5/91; H04N5/92; H04N5/923; G; G11; G11B; G11B23/00; G11B23/0007; H04N9/00; H04N9/79; H04N9/793; H04N9/7933; H04N9/7936
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
142 words
An arrangement for equalizing a video signal in a system in which the video signal is recorded in frequency modulated form and then played back upon frequency demodulation, wherein, in addition to a pre-emphasis circuit with an emphasizing factor in the recording channel, and similarly in addition to a de-emphasis circuit in the playback channel, a group-delay equalization circuit for the video signal is provided such that in a curve representing the frequency response on the output side of the frequency modulator, overshoot spikes of opposite polarity are simultaneously and substantially symmetrically produced for a black/white transition as well as a white/black transition, of the incoming video signal and such that, in light of the attendant reduction in overshoot, the emphasizing factor is increased until the overshoot limits represented by the maximum and minimum permissible frequencies of the system have been reached.
Claim 2
Dependent Claim
142 words
An arrangement for equalizing a video signal in a system in which the video signal is recorded in frequency modulated form and then played back upon frequency demodulation, wherein, in addition to a pre-emphasis circuit with an emphasizing factor in the recording channel, and similarly in addition to a de-emphasis circuit in the playback channel, a group-delay equalization circuit for the video signal is provided such that in a curve representing the frequency response on the output side of the frequency modulator, overshoot spikes of opposite polarity are simultaneously and substantially symmetrically produced for a black/white transition as well as a white/black transition, of the incoming video signal and such that, in light of the attendant reduction in overshoot, the emphasizing factor is increased until the overshoot limits represented by the maximum and minimum permissible frequencies of the system have been reached.
Claim 3
Dependent Claim
172 words
An arrangement for equalizing a video signal in a system in which the video signal is recorded in frequency modulated form and then played back upon frequency demodulation, wherein, in addition to a pre-emphasis circuit with an emphasizing factor U G in the recording channel, and similarly in addition to a de-emphasis cirucit in the playback channel, a group-delay equalization circuit for the video signal is provided such that in a curve representing the frequency response on the output side of the frequency modulator, overshoot spikes of opposite polarity are simultaneously and substantially symmetrically produced for a black/white transition as well as a white/black transition, of the incoming video signal and that the emphasizing factor U G of the pre-emphasis circuit is increased and follows the equation: U.sub.G =2U-1 where U is the emphasizing factor of the pre-emphasis circuit without supplementation by the group delay equalization circuit and U is determined by the fraction U=(f 2 /f 1 ) of the cut-off frequencies f 2 and f 1 of the pre-emphasis circuit.
Claim 4
Dependent Claim
172 words
An arrangement for equalizing a video signal in a system in which the video signal is recorded in frequency modulated form and then played back upon frequency demodulation, wherein, in addition to a pre-emphasis circuit with an emphasizing factor U G in the recording channel, and similarly in addition to a de-emphasis cirucit in the playback channel, a group-delay equalization circuit for the video signal is provided such that in a curve representing the frequency response on the output side of the frequency modulator, overshoot spikes of opposite polarity are simultaneously and substantially symmetrically produced for a black/white transition as well as a white/black transition, of the incoming video signal and that the emphasizing factor U G of the pre-emphasis circuit is increased and follows the equation: U.sub.G =2U-1 where U is the emphasizing factor of the pre-emphasis circuit without supplementation by the group delay equalization circuit and U is determined by the fraction U=(f 2 /f 1 ) of the cut-off frequencies f 2 and f 1 of the pre-emphasis circuit.
References Cited (Backward Citations)
US3122716A
Cited
US3340367A
Cited
US3518581A
Cited
US3564123A
Cited
US3728475A
Cited
US3800265A
Cited
US3868604A
Cited
US4140983A
Cited
US4071782A
Cited
US4200889A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1985-09-06 | 1986-03-08 | 1986-09-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-09-06 | 1990-03-08 | 1990-09-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-09-06 | 1994-03-08 | 1994-09-07 | $7700.00 | Window Closed / Lapsed |