US3721755A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Color television encoder modulator
Assignee: Telemation Inc
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Filing: 1971-03-29
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Granted: 1973-03-20
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Expires: 1991-03-29
Abstract
Abstract A balanced modulator circuit for use in television cameras to impress color information on the chrominance subcarrier wherein the video input is phase-split and the resulting signals are fed through respective bootstrap emitter-followers, the outputs of these emitter-followers are chopped by respective field effect transistors gated by respective 3.58MHz clock signals which are 180* out of phase and a third field effect transistor, operated in a saturation mode wherein 10 ma. forward current is drawn, is connected across the outputs of the emitter-followers and gated by clamp source pulses to clamp the emitter-follower outputs at zero reference.
Inventors
- 👤 P Craig
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 02:47
CPC Classifications
H; H03; H03C; H03C1/00; H03C1/52; H03C1/54; H03C1/542; H04; H04N; H04N9/00; H04N9/64; H04N9/65
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
241 words
A balanced modulator circuit comprising: a phase splitter for receiving a video input and producing two output signals having equal magnitudes but opposite polarities; a pair of bootstrap emitter-followers each connected To receive a respective one of said outputs from said phase splitter; a clamping circuit formed by a clamping field effect transistor, having a capacitor coupling the drain electrode of said clamping transistor to the output of one of said emitterfollowers and having the source electrode of said clamping transistor connected to the output of the other of said emitter-followers, and a source of clamping pulses connected to supply the gate electrode of said clamping transistor; a chopper circuit formed by a pair of chopping field effect transistors having the source electrode of one of said chopping transistors connected to the drain electrode of said clamping transistor and having the source electrode of the other of said chopping transistors connected to the source electrode of said clamping transistor while the drain electrodes of said chopping transistors are connected together to provide a chopper output; and a clock source generating two square wave signals at 3.58MHz, one of said signals having 0* phase and the other of said signals having 180* phase, and connected to apply said one of said signals to the gate electrode of said one of said chopping transistors and to apply the other of said signals to the gate electrode of said other of said chopping transistors.
Claim 2
Dependent Claim
241 words
A balanced modulator circuit comprising: a phase splitter for receiving a video input and producing two output signals having equal magnitudes but opposite polarities; a pair of bootstrap emitter-followers each connected To receive a respective one of said outputs from said phase splitter; a clamping circuit formed by a clamping field effect transistor, having a capacitor coupling the drain electrode of said clamping transistor to the output of one of said emitterfollowers and having the source electrode of said clamping transistor connected to the output of the other of said emitter-followers, and a source of clamping pulses connected to supply the gate electrode of said clamping transistor; a chopper circuit formed by a pair of chopping field effect transistors having the source electrode of one of said chopping transistors connected to the drain electrode of said clamping transistor and having the source electrode of the other of said chopping transistors connected to the source electrode of said clamping transistor while the drain electrodes of said chopping transistors are connected together to provide a chopper output; and a clock source generating two square wave signals at 3.58MHz, one of said signals having 0* phase and the other of said signals having 180* phase, and connected to apply said one of said signals to the gate electrode of said one of said chopping transistors and to apply the other of said signals to the gate electrode of said other of said chopping transistors.
Claim 3
Dependent Claim
17 words
The device of claim 1 further comprising: a double cascode emitter-follower connected to receive said chopper output.
Claim 4
Dependent Claim
18 words
The device of claim 1 wherein: each said transistor is a depletion type junction field effect transistor chopper.
Claim 5
Independent Claim
90 words
The method of double balanced modulation to impress color information on the chrominance signal of a color television camera, said method comprising the steps of: phase splitting the video input to provide two phases of video signals having equal magnitudes and opposite polarities; clamping said two video signals when the value of said video input is zero to prevent subcarrier output; and field effect chopping said two video signals at a predetermined rate when said video input has a value other than zero to provide a color modulated subcarrier output.
Claim 6
Independent Claim
90 words
The method of double balanced modulation to impress color information on the chrominance signal of a color television camera, said method comprising the steps of: phase splitting the video input to provide two phases of video signals having equal magnitudes and opposite polarities; clamping said two video signals when the value of said video input is zero to prevent subcarrier output; and field effect chopping said two video signals at a predetermined rate when said video input has a value other than zero to provide a color modulated subcarrier output.
Claim 7
Dependent Claim
11 words
The method of claim 4 wherein: said predetermined rate is 3.58MHz.
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) | 1976-03-19 | 1976-09-18 | 1977-03-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-03-19 | 1980-09-18 | 1981-03-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-03-19 | 1984-09-18 | 1985-03-20 | $7700.00 | Window Closed / Lapsed |