U.S. patents available from 1976 to present.
U.S. patent applications available from 2005 to present.

Quadrature amplitude modulation with line synchronization pulse for video telephone

Patent 4918718 Issued on April 17, 1990. Estimated Expiration Date: Icon_subject June 28, 2008. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.

Patent References

3517117

Logarithmic color matrix for a digital television receiver
Patent #: 4544945
Issued on: 10/01/1985
Inventor: Lewis, Jr. ,   et al.

Data compression apparatus and method for encoding and decoding multi-line signals
Patent #: 4562467
Issued on: 12/31/1985
Inventor: Bradley

Video-optimized modulator-demodulator with adjacent modulating amplitudes matched to adjacent pixel gray values
Patent #: 4739413
Issued on: 04/19/1988
Inventor: Meyer

Suppressed double-sideband communication system Patent #: 4780884
Issued on: 10/25/1988
Inventor: Karabinis

Inventors

Assignee

Application

No. 212549 filed on 06/28/1988

US Classes:

348/14.12, Transmission control (e.g., resolution or quality)358/469, Carrier wave modulation375/261, Quadrature amplitude modulation379/93.31Protocol

Examiners

Primary: Ng, Jin F.
Assistant: Chan, Wing F.

Attorney, Agent or Firm

International Classes

H04M 011/00
H04L 027/20
H04L 027/22

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.

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