Ghost removing system for use in television receiver
AssigneeMatsushita Electric Industrial Co., Ltd.
InventorNamio Yamaguti
Life of this patent
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Abstract
Ghost phenomenon on a screen of a television receiver is removed by supplying an intermediate frequency video signal including a desired signal and a ghost signal to a pair of parallel circuits, each including a synchronous or multiplication detection circuit. The detection axis or reference phase of the first detection circuit differs from the second detection axis or reference phase by an amount equal to the phase difference between the desired signal and the ghost signal. Either the detected video signal in one of the parallel circuits or the intermediate frequency signal applied to one of the parallel circuits is delayed an amount equal to the delay time between the desired signal and ghost signal, and the signals from both circuits are combined in a suitable ratio to cancel the ghost signal.
Claims18
A method for removing a ghost wave received together with a desired wave in a television receiver, comprising the steps of
- synchronously detecting a video intermediate frequency signal in the television receiver at a first reference phase to provide a first composite video output;
- synchronously detecting the video intermediate frequency signal at a second reference phase, which differs from said first reference phase by an angle corresponding to a phase difference between the ghost wave and the desired wave, to provide a second composite video output;
- delaying at least one of said video intermediate frequency signal, said first composite video, and said second composite video, an amount to cause said ghost wave in one of said composite video outputs to be in time coincidence with the desired wave in the other of said composite video outputs, and
- combining said composite video outputs after said delay in a suitable ratio to cause said time coincident ghost wave in one of said composite video outputs and desired wave in the other of said composite video outputs to cancel each other.
In a television receiver, apparatus for removing the ghost wave received together with the desired wave, said television receiver being of the type which converts the received signals into a video intermediate frequency signal, the apparatus for removing comprising,
- a. first means for synchronously detecting, at a first reference phase, said video intermediate frequency signal to provide a first composite video output signal,
- b. second means for synchronously detecting, at a second variable reference phase said video intermediate frequency signal to provide a second composite video output signal,
- c. variable delay means for adjustably, variably delaying at least one of said video intermediate frequency signals before application to said second means, said first video composite output signal, and said second video composite output signal to thereby adjust the relative times of said ghost and desired waves in said first and second composite video output signals, and
- d. means for combining said composite video output signals in a controllable ratio, whereby adjustments of said variable phase, said variable delay and said controllable ratio may be selected for removing said ghost wave.
Dependencies are inferred from the claim text.