Patent US3832486A successfully refreshed from Google Patents.
US3832486A
Expired / Lapsed
US
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Modulator clamp circuit
Assignee: Thomas International Corp
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Filing: 1973-03-16
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Granted: 1974-08-27
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Expires: 1993-03-16
Abstract
Abstract A video tape recorder system includes a modulator circuit for modulating an RF carrier with video information derived from scanning a video tape. The modulator circuit is formed by a differential amplifier with a series capacitor-resistor network between a pair of inputs of the differential amplifier to effectively cancel, by means of common mode rejection, an AC portion of the video information. A diode-capacitor network connected with one differential amplifier input reinserts DC into the video information signal, and forms a part of a temperature compensated bias supply for the inputs of the differential amplifier.
Inventors
- 👤 P Wanek
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 22:39
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/38; H04N5/40
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
94 words
A modulator circuit for modulating a carrier signal with a modulating signal, comprising: differential amplifier means having at least a first input, and a second input, carrier input means for coupling the carrier signal to the differential amplifier means, modulating input means for coupling the modulating signal to the first input, and common mode means for deriving from the modulating signal a cancellation signal which is AC coupled to the second input, the differential amplifier means effectively subtracting the cancellation signal from the modulation signal at the first input due to common mode rejection.
Claim 2
Dependent Claim
94 words
A modulator circuit for modulating a carrier signal with a modulating signal, comprising: differential amplifier means having at least a first input, and a second input, carrier input means for coupling the carrier signal to the differential amplifier means, modulating input means for coupling the modulating signal to the first input, and common mode means for deriving from the modulating signal a cancellation signal which is AC coupled to the second input, the differential amplifier means effectively subtracting the cancellation signal from the modulation signal at the first input due to common mode rejection.
Claim 3
Dependent Claim
27 words
The modulator circuit of claim 1 wherein said common mode means comprises capacitor means and resistive means in series between the first input and the second input.
Claim 4
Dependent Claim
33 words
The modulator circuit of claim 1 wherein said modulating input means includes a DC reinsertion network for DC offsetting the modulating signal in proportion to the average DC value of the modulating signal.
Claim 5
Dependent Claim
68 words
The modulator circuit of claim 3 wherein said DC reinsertion network includes DC potential means for establishing a fixed DC level at a potential junction, diode means, capacitor means, means connecting said diode means and said capacitor means in series between said potential junction and a source of said modulating signal, with the connection between the diode means and the capacitor means being coupled to said first input.
Claim 6
Dependent Claim
30 words
The modulator circuit of claim 4 wherein said DC reinsertion network includes resistive means coupled in shunt across said diode means, said resistive means having a substantially high resistance value.
Claim 7
Dependent Claim
55 words
The modulator circuit of claim 4 wherein said DC potential means comprises a plurality of resistors connected in series to form a voltage divider, and capacitor means in shunt with at least one of said plurality of resistors to maintain said potential junction at said fixed DC level regardless of fluctuations in said modulating signal.
Claim 8
Dependent Claim
52 words
The modulator circuit of claim 1 including first bias means for DC coupling a first DC bias to the first input, second bias means for DC coupling a second DC bias to said second input, said first and second bias means having compensating voltage changes for a temperature change in the ciRcuit.
Claim 9
Dependent Claim
103 words
A modulator circuit for amplitude modulating an RF carrier signal with a video signal having a video component and a recurring sync pulse component, comprising: differential amplifier means having input means and output means for the amplitude modulated signal, carrier input means for coupling the RF carrier signal to the input means, and modulating input means for coupling the video signal to the first input means including diode means, capacitor means, and network means connecting said diode means and said capacitor means to produce in the video signal a varying DC offset in proportion to the average DC value of the video signal.
Claim 10
Dependent Claim
103 words
A modulator circuit for amplitude modulating an RF carrier signal with a video signal having a video component and a recurring sync pulse component, comprising: differential amplifier means having input means and output means for the amplitude modulated signal, carrier input means for coupling the RF carrier signal to the input means, and modulating input means for coupling the video signal to the first input means including diode means, capacitor means, and network means connecting said diode means and said capacitor means to produce in the video signal a varying DC offset in proportion to the average DC value of the video signal.
Claim 11
Dependent Claim
65 words
The modulator circuit of claim 8 wherein said modulating input means includes potential means for establishing a fixed potential at a potential junction, said network means connects said diode means and said capacitor means in series between said potential junction and a supply junction carrying the video signal, and means coupling the connection between the diode means and the capacitor means to said input means.
Claim 12
Dependent Claim
45 words
The modulator circuit of claim 9 wherein said modulating input means includes common mode means for deriving from the video signal a cancellation signal which is supplied to said input means, the differential amplifier means effectively subtracting the cancellation signal due to common mode rejection.
Claim 13
Dependent Claim
30 words
The modulator circuit of claim 10 wherein said common mode means includes a capacitor and a resistor in series between a pair of input terminals for said differential amplifier means.
Claim 14
Dependent Claim
55 words
The modulator circuit of claim 9 including a second potential means for establishing a second fixed potential at a second potential junction, and second diode means for connecting said second potential junction to said input means, the potential means having similar components to cause the fixed potentials to track for temperature variations in the circuit.
Claim 15
Dependent Claim
50 words
The modulator circuit of claim 8 wherein said modulating input means includes potentiometer means for varying the magnitude of the video signal which is coupled to the network means, the potentiometer means being adjustable to provide a perdetermined percentage modulation level for the amplitude modulated signal at said output means.
Claim 16
Dependent Claim
64 words
The modulator circuit of claim 8 including first bias means for supplying a first DC bias to said input means, second bias means for supplying a second DC bias to said input means, said first and second DC biases causing the differential amplifier means to produce a negative modulation signal with the sync pulse components producing maximum amplitude modulation of the RF carrier signal.
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) | 1977-08-26 | 1978-02-25 | 1978-08-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-08-26 | 1982-02-25 | 1982-08-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-08-26 | 1986-02-25 | 1986-08-27 | $7700.00 | Window Closed / Lapsed |