Patent US3773979A successfully refreshed from Google Patents.
US3773979A
Expired / Lapsed
US
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Multiplexed video and subcarrier microwave communications system
Assignee: Digital Communications Inc
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Filing: 1972-03-30
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Granted: 1973-11-20
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Expires: 1992-03-30
Abstract
Abstract A microwave communications system propagates video information and a high grade wide band subcarrier channel notwithstanding substantial differential phase and differential gain (system nonlinearities) exhibited by the microwave transmitter. The supplementary information is quantized (if not already digital in form), and is employed to differentially modulate (in discrete increments given by multiples of pi /2) the phase of a quadraphase carrier, i.e., in a non-return to zero mode of operation. At the receiver, the modulated subcarrier spectrum is recovered by filtering, and the subcarrier information recovered by comparing the subcarrier phase difference between consecutive time slots. Since the absolute amplitude of differential phase varies slowly at the transmitter vis-a-vis the subcarrier modulation frequency (substantially 15.734 kHz versus several hundred thousand Hz, or several megacycles), error-free subcarrier demodulation may be effected even in systems exhibiting large differential phase variations.
Inventors
- 👤 D Kirk
- 👤 M Paolini
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 03:41
CPC Classifications
H; H04; H04N; H04N7/00; H04N7/08; H04N7/081; H04J; H04J9/00
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
167 words
In combination in multiplexed communications apparatus, transmitter means for radiating a modulated main carrier, said main carrier modulating spectrum comprising a base band signal and a subcarrier channel, said transmitter including a modulator characterized by significant phase non-linearities when operated over a substantial part of its operating range, means for supplying said base band signal to said modulator for operating said modulator over said substantial part of its operating range, and means for supplying said subcarrier channel signal to said modulator, said subcarrier signal being substantially smaller in amplitude than said base band signal, said subcarrier channel supplying means comprising means for generating plural distinct subcarrier phases, digital intelligence supplying means, controlled gating means for gating a selected one of said subcarrier phases to said modulator, means for storing information identifying the subcarrier phase supplied to said modulator, and arithmetic means responsive to the stored contents of said storing means and to the digital intelligence supplied by said supplying means for selectively controlling said controlled gating means.
Claim 2
Dependent Claim
167 words
In combination in multiplexed communications apparatus, transmitter means for radiating a modulated main carrier, said main carrier modulating spectrum comprising a base band signal and a subcarrier channel, said transmitter including a modulator characterized by significant phase non-linearities when operated over a substantial part of its operating range, means for supplying said base band signal to said modulator for operating said modulator over said substantial part of its operating range, and means for supplying said subcarrier channel signal to said modulator, said subcarrier signal being substantially smaller in amplitude than said base band signal, said subcarrier channel supplying means comprising means for generating plural distinct subcarrier phases, digital intelligence supplying means, controlled gating means for gating a selected one of said subcarrier phases to said modulator, means for storing information identifying the subcarrier phase supplied to said modulator, and arithmetic means responsive to the stored contents of said storing means and to the digital intelligence supplied by said supplying means for selectively controlling said controlled gating means.
Claim 3
Dependent Claim
41 words
In combination as in claim 1 wherein said transmitter further comprises a clock, a digital counter cycled by said clock, logic decoding means connected to said counter, and means responsive to said digital decoding means for selectively modulating said subcarrier channel.
Claim 4
Dependent Claim
26 words
A combination as in claim 1 wherein said transmitter digital intelligence supplying means includes time division multiplexing means for supplying digital information to said arithmetic means.
Claim 5
Dependent Claim
24 words
A combination as in claim 1, wherein said plural subcarrier phase supplying means supplies four distinct subcarrier phases each separated by 90 electrical degrees.
Claim 6
Dependent Claim
49 words
A combination as in claim 1 further comprising receiver means, said receiver means comprising filter means for separating said video and said subcarrier signals, and subcarrier phase demodulator means, said demodulator means including means for determining the difference in phase of the received subcarrier during consecutive periods of time.
Claim 7
Dependent Claim
41 words
A combination as in claim 5 wherein said subcarrier demodulator means comprises delay means, phase splitter means, and plural Exclusive OR logic means each receiving the output of said delay means and a different phase supplied by said phase splitter means.
Claim 8
Dependent Claim
43 words
A combination as in claim 6 further comprising plural signal averaging means each connected to the output of a different one of said Exclusive OR logic means, and means for determining which of said plural signal averaging means exhibits the largest output potential.
Claim 9
Dependent Claim
62 words
A combination as in claim 5 wherein said transmitter digital intelligence supplying means comprises plural signal sources and time division multiplexing means for sequentially connecting a measure of the signals supplied by said signal sources to said arithmetic means, and wherein said receiver includes time division demultiplexing means for separating recovering said signals supplied by said plural signal sources at said transmitter.
Claim 10
Dependent Claim
35 words
A combination as in claim 8 further comprising clock means at said transmitter, saId receiver including phase locked loop means for producing an output wave of like frequency as that supplied by said clock means.
Claim 11
Dependent Claim
36 words
A combination as in claim 9 wherein said transmitter includes counter means cycled by said clock means, and said phase locked loop includes counter means of a capacity corresponding to that of said transmitter counter means.
Claim 12
Dependent Claim
44 words
A combination as in claim 10 wherein said transmitter further comprisis means responsive to a reference state of said transmitter counter means for amplitude modulating said subcarrier signal, and wherein said receiver includes amplitude modulation detector means for signalling said phase locked loop means.
Claim 13
Dependent Claim
148 words
In combination in multiplex microwave communication apparatus, a microwave frequency modulator, said modulator being characterized by significant phase non-linearities when deviated over a substantial portion of its transfer characteristic, means for supplying a microwave main carrier frequency deviating modulating potential to said modulator, said microwave deviating potential comprising a relatively large amplitude base band video signal which operates said modulator over said substantial portion of its transfer characteristic, said modulating potential supplied by said supplying means also including a differential phase modulated subcarrier, said modulated subcarrier being substantially higher in frequency than said base band video signal and being substantially smaller in amplitude than said video signal, means for supplying said video signal to said modulator deviating potential supplying means, and means for supplying said differential phase modulated subcarrier to said modulator deviating potential supplying means, said modulated subcarrier supplying means comprising digital differential subcarrier phase modulating means.
Claim 14
Dependent Claim
148 words
In combination in multiplex microwave communication apparatus, a microwave frequency modulator, said modulator being characterized by significant phase non-linearities when deviated over a substantial portion of its transfer characteristic, means for supplying a microwave main carrier frequency deviating modulating potential to said modulator, said microwave deviating potential comprising a relatively large amplitude base band video signal which operates said modulator over said substantial portion of its transfer characteristic, said modulating potential supplied by said supplying means also including a differential phase modulated subcarrier, said modulated subcarrier being substantially higher in frequency than said base band video signal and being substantially smaller in amplitude than said video signal, means for supplying said video signal to said modulator deviating potential supplying means, and means for supplying said differential phase modulated subcarrier to said modulator deviating potential supplying means, said modulated subcarrier supplying means comprising digital differential subcarrier phase modulating means.
Claim 15
Dependent Claim
93 words
A combination as in claim 12 wherein said differential phase subcarrier modulating means comprises means for producing plural subcarrier signals of like frequency but which differ in phase, controlled gate means for selectively gating one of said subcarrier phases to said modulator deviating potential supplying means, digital information supplying means, and arithmetic unit means for selectively enabling said controlled gating means responsive to the incoming digital information supplied by said source thereof and further responsive to digital information representative of the instantaneous carrier phase gated to said main carrier deviating potential supplying means.
Claim 16
Dependent Claim
32 words
A combination as in claim 13 wherein said digital information supplying means comprises at least one analog signal source, analog-to-digital converting means, and means for converting parallel digital signals to serial form.
Claim 17
Dependent Claim
45 words
A combination as in claim 13 wherein said digital information supplying means comprises plural signal sources, time division multiplexing means for sampling said signal sources means for converting said analog signals to digital form, and means for serially supplying digital information to said arithmetic means.
Claim 18
Dependent Claim
39 words
A combination as in claim 13 wherein said digital information supplying means supplies two synchronous serial binary wave trains, and wherein said plural phase subcarrier producing means comprises means for producing four subcarrier phases separated by pi /2 radians.
Claim 19
Dependent Claim
62 words
A combination as in claim 12 further comprising receiver means for receiving the modulated main microwave carrier, receiver means including means for separating said base band video and said modulated subcarrier signals, and means for demodulating said modulated subcarrier, said demodulating means comprising means responsive to the difference in phase of said subcarrier during consecutive time periods for signalling the modulating intelligence.
Claim 20
Dependent Claim
40 words
A combination as in claim 17 wherein said modulated subcarrier demodulating means comprises Exclusive OR means for comparing plural phase versions of the modulated subcarrier during one time period with the phase of the carrier during an Adjacent time period.
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) | 1976-11-19 | 1977-05-21 | 1977-11-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-11-19 | 1981-05-21 | 1981-11-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-11-19 | 1985-05-21 | 1985-11-20 | $7700.00 | Window Closed / Lapsed |