Quadrature amplitude modulation with line synchronization pulse for
video telephone
    4.
    发明授权
    Quadrature amplitude modulation with line synchronization pulse for video telephone 失效
    视频电话线路同步脉冲的正交幅度调制

    公开(公告)号:US4918718A

    公开(公告)日:1990-04-17

    申请号:US212549

    申请日:1988-06-28

    CPC classification number: H04N1/646 H04N7/147

    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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