US4918718A
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Quadrature amplitude modulation with line synchronization pulse for video telephone
Assignee: Mitsubishi Electronics America Inc
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Filing: 1988-06-28
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Granted: 1990-04-17
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Expires: 2008-06-28
Abstract
Abstract The present invention assigns amplitudes of sine wave cycles in a data packet on I and Q channels of a QAM signal to color, gray or luminance values. Overlapping sine wave cycles on the I and Q channels in the data packet are assigned to the same or neighboring pixels. A synchronizing signal is sent at the beginning of each transmission of a packet. The synchronizing signal is a plurality of cycles at a maximum amplitude on the I and Q channels. The synchronizing signal serves two functions simultaneously. First, it is used to indicate the beginning of a new packet. Second, the phase of the synchronizing signal is used to initialize the demodulator phase detecting circuitry.
Inventors
- 👤 Lawrence D. Emmons
- 👤 Gary Fletcher, Jr.
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 23:24
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/46; H04N1/64; H04N1/646; H04N7/00; H04N7/14; H04N7/141; H04N7/147
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
115 words
A method for transmitting data corresponding to pixels in a video image over a telephone line using quadrature amplitude modulation (QAM) with in-phase (I) and quadrature (Q) channels, comprising the steps of; assigning adjacent amplitudes of sine waves in a data packet on said I and Q channels to adjacent color, gray or luminance values; assigning overlapping sine wave cycles on said I and Q channels in said data packet to the same or neighboring pixels; transmitting a synchronizing signal at the beginning of each transmission of a data packet, said synchronizing signal being a plurality of cycles on said I and Q channels; and initializing a demodulator to the phase of said synchronizing signal.
Claim 2
Independent Claim
115 words
A method for transmitting data corresponding to pixels in a video image over a telephone line using quadrature amplitude modulation (QAM) with in-phase (I) and quadrature (Q) channels, comprising the steps of; assigning adjacent amplitudes of sine waves in a data packet on said I and Q channels to adjacent color, gray or luminance values; assigning overlapping sine wave cycles on said I and Q channels in said data packet to the same or neighboring pixels; transmitting a synchronizing signal at the beginning of each transmission of a data packet, said synchronizing signal being a plurality of cycles on said I and Q channels; and initializing a demodulator to the phase of said synchronizing signal.
Claim 3
Dependent Claim
33 words
The method of claim 1 wherein said synchronizing signal is at a maximum amplitude, and further comprising the steps of calibrating a demodulator amplitude detector to said maximum amplitude of said synchronizing signal.
Claim 4
Dependent Claim
38 words
The method of claim 1 wherein said adjacent amplitudes are assigned to adjacent shades of gray, with black and darker shades of gray having a first phase and white and lighter shades of gray having a second phase.
Claim 5
Dependent Claim
84 words
The method of claim 1 wherein color information is transmitted, with luminance data being transmitted first, followed by color difference data, said luminance data for the pixels in a first line being transmitted sequentially on the I or Q channel, with the luminance data for the pixels on a second adjacent line being transmitted sequentially on the other channel, followed by average color difference data from lines 1 and 2 being transmitted sequentially on I and Q channels for said first and second lines.
Claim 6
Dependent Claim
23 words
The method of claim 4 wherein a greater number of cycles are assigned to said luminance data than to said color difference data.
Claim 7
Dependent Claim
17 words
The method of claim 1 wherein every nth synchronizing signal indicates the beginning of a new line.
Claim 8
Independent Claim
121 words
A system for transmitting data corresponding to pixels in a video image over a telephone line using quadrature amplitude modulation (QAM) with in-phase (I) and quadrature (Q) channels, comprising: means for assigning adjacent amplitudes of sine waves in a data field on said I and Q channels to adjacent color, gray or luminance values; means for assigning overlapping sine wave cycles on said I and Q channels in said data field to the same or neighboring pixels; means for transmitting a synchronizing signal at the beginning of each transmission of a QAM data packet, said synchronizing signal being a plurality of cycles on said I and Q channels; and means for initializing a demodulator to the phase of said synchronizing signal.
Claim 9
Independent Claim
121 words
A system for transmitting data corresponding to pixels in a video image over a telephone line using quadrature amplitude modulation (QAM) with in-phase (I) and quadrature (Q) channels, comprising: means for assigning adjacent amplitudes of sine waves in a data field on said I and Q channels to adjacent color, gray or luminance values; means for assigning overlapping sine wave cycles on said I and Q channels in said data field to the same or neighboring pixels; means for transmitting a synchronizing signal at the beginning of each transmission of a QAM data packet, said synchronizing signal being a plurality of cycles on said I and Q channels; and means for initializing a demodulator to the phase of said synchronizing signal.
Claim 10
Dependent Claim
32 words
The system of claim 7 wherein said synchronizing signal is at a maximum amplitude and further comprising means for calibrating a demodulator amplitude detector to said maximum amplitude of said synchronizing signal.
Claim 11
Dependent Claim
50 words
The system of claim 7 further comprising: means for transmitting a carrier frequency initialization signal; means for determining an average center frequency from a received carrier frequency initialization signal; and a microprocessor for detecting said carrier frequency initialization signal and enabling said means for determining only during said initialization signal.
Claim 12
Dependent Claim
35 words
The system of claim 7 wherein said means for initializing comprises a phase lock loop (PLL) and further comprising a microprocessor for detecting said synchronizing signals and enabling said PLL only during said synchronizing signals.
Claim 13
Dependent Claim
29 words
The system of claim 7 wherein said means for assigning adjacent amplitudes comprises a memory look-up table and said means for assigning overlapping sine wave cycles comprises a microprocessor.
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) | 1993-04-16 | 1993-10-16 | 1994-04-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-04-16 | 1997-10-16 | 1998-04-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-04-16 | 2001-10-16 | 2002-04-17 | $7700.00 | Window Closed / Lapsed |