Patent US3674927A successfully refreshed from Google Patents.
US3674927A
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Video shading modulator with paraphase control signals applied respectively to variable impedance devices in series and in parallel with the video signal path
Assignee: General Electric Co
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Filing: 1971-03-16
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Granted: 1972-07-04
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Expires: 1991-03-16
Abstract
Abstract To correct for degrading optical and pickup tube effects, amplitude of a video signal is varied by a shading signal. The shading signal is furnished to the input of a phase splitter and the resulting signals of opposite phase are furnished to respective gates of a pair of closely matched, variable impedance devices, such as field effect transistors, one such device being connected in series with the video signal path and the other such device being connected in shunt with the video signal path. By using matched field effect transistors as the variable impedance devices, their quiescent output resistances are substantially identical and the circuit, therefore, exhibits symmetry.
Inventors
- 👤 Thomas M Jordan Jr
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 23:44
CPC Classifications
H; H04; H04N; H04N23/00; H04N23/80; H04N23/81
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
121 words
A video signal shading modulator comprising: first and second controllable output resistance devices, said first device being connected in series with circuitry transmitting a video signal and said second device being connected in parallel with said circuitry transmitting said video signal; and shading signal generating circuitry producing first and second output signals of similar waveform but opposite polarity, said shading signal generating circuitry being coupled to a control input of said first and second controllable output resistance devices, respectively, so that said first output signal controls output resistance of said first device and said second output signal controls output resistance of said second device such that output resistance of said first device varies inversely with output resistance of said second device.
Claim 2
Dependent Claim
121 words
A video signal shading modulator comprising: first and second controllable output resistance devices, said first device being connected in series with circuitry transmitting a video signal and said second device being connected in parallel with said circuitry transmitting said video signal; and shading signal generating circuitry producing first and second output signals of similar waveform but opposite polarity, said shading signal generating circuitry being coupled to a control input of said first and second controllable output resistance devices, respectively, so that said first output signal controls output resistance of said first device and said second output signal controls output resistance of said second device such that output resistance of said first device varies inversely with output resistance of said second device.
Claim 3
Dependent Claim
92 words
The video signal shading modulator of claim 1 wherein said first and second controllable output resistance devices each comprises a field effect transistor having source, drain and gate electrodes, said source electrodes being connected to each other, said gate electrode of said first field effect transistor receiving said first output signal from said shading signal generating circuitry, said gate electrode of said second field effect transistor receiving said second output signal from said shading signal generating circuitry, and said drain electrode of said first field effect transistor receiving the unmodulated video signal.
Claim 4
Dependent Claim
27 words
The video signal shading modulator of claim 2 wherein said first and second field effect transistor are formed in common on a single crystal of semiconductor material.
Claim 5
Dependent Claim
51 words
The video signal shading modulator of claim 1 wherein said shading signal generating circuitry comprises signal generator means for producing repetitive signals of controllable waveform shape and phase splitter circuitry coupled to said signal generator means for producing the inverse of said controllable waveform shape produced by said signal generator means.
Claim 6
Dependent Claim
78 words
The video signal shading modulator of claim 4 wherein said signal generator means comprises horizontal rate sawtooth and parabola waveform generators and vertical rate sawtooth and parabola waveform generators, selector means coupled to each of said waveform generators, respectively, for selectively controlling polarity and amplitude of each of said horizontal rate and vertical rate waveforms, respectively, and summation means coupled to each of said selector means for algebraically combining the signals produced by each of said selector means.
Claim 7
Dependent Claim
93 words
The video signal shading modulator of claim 5 wherein each of said first and second controllable output resistance devices comprises a field effect transistor having source, drain and gate electrodes, said source electrodes being connected to each other, said gate electrode of said first field effect transistor receiving said first output signal from said shading signal generating circuit, said gate electrode of said second field effect transistor receiving said second output signal from said shading signal generating circuitry, and said drain eLectrode of said first field effect transistor receiving the unmodulated video signal.
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) | 1975-07-04 | 1976-01-03 | 1976-07-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-07-04 | 1980-01-03 | 1980-07-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-07-04 | 1984-01-03 | 1984-07-04 | $7700.00 | Window Closed / Lapsed |