Multiple QAM digital television signal decoder
First Claim
Patent Images
1. In a system for processing a television signal, digital signal processing apparatus comprising:
- input means for receiving a multiple carrier composite QAM signal conveying data occupying given locations in a grid-like constellation;
signal conditioning means, including adaptive equalizer means, responsive to said composite signal for providing a conditioned composite signal at an output, said equalizer means including a single equalizing device having a wideband response encompassing more than one of said carriers and defined by one set of coefficients for equalizing said more than one carriers without separating said more than one carriers from the spectrum of said composite signal prior to equalization;
means for deriving an error signal representing a condition of said QAM signal; and
means for coupling said error signal to said signal conditioning means.
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Abstract
In a video signal processing system, a single adaptive passband equalizer is used to process a composite Quadrature Amplitude Modulated (QAM) signal encoded with high priority (HP) and standard priority (SP) components. The equalizer output is phase corrected by a de-rotator, and filtered to separate the HP and SP components. Error signals respectively representing HP and SP phase errors are developed. One of the error signals controls the operation of the de-rotator. Both error signals are used to generate updated coefficients for the adaptive equalizer. Afterwards the HP and SP components are decoded and combined.
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Citations
14 Claims
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1. In a system for processing a television signal, digital signal processing apparatus comprising:
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input means for receiving a multiple carrier composite QAM signal conveying data occupying given locations in a grid-like constellation; signal conditioning means, including adaptive equalizer means, responsive to said composite signal for providing a conditioned composite signal at an output, said equalizer means including a single equalizing device having a wideband response encompassing more than one of said carriers and defined by one set of coefficients for equalizing said more than one carriers without separating said more than one carriers from the spectrum of said composite signal prior to equalization; means for deriving an error signal representing a condition of said QAM signal; and means for coupling said error signal to said signal conditioning means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. In a system for processing a television signal, digital signal processing apparatus comprising:
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input means for receiving a composite multiple carrier QAM signal conveying data symbols occupying given locations in a grid-like constellation, said multiple carrier composite signal comprising a first carrier modulated by a first component, and a second carrier modulated by a second component; signal conditioning means including (a) adaptive equalizer means exhibiting non-time-multiplexed operation and responsive to said composite signal for providing an equalized composite signal at an output, said equalizer means including a single equalizing device having a response encompassing said first and second modulated carriers for equalizing said first and second modulated carriers without separating said first and second modulated carriers from the spectrum of said composite signal prior to equalization; and
(b) de-rotator means for maintaining a desired orientation of said constellation;means for separating said first component and said second component of a conditioned composite signal from said conditioning means; first means responsive to separated symbols associated with said first component for producing corresponding output symbols at a respective predetermined coordinates; first detector means for producing a first error signal representing an offset between coordinates of respectively corresponding input and output symbols of said first means; second means responsive to separated symbols associated with said second component for producing corresponding output symbols at respective predetermined coordinates; second detector means for producing a second error signal representing an offset between coordinates of respectively corresponding input and output symbols of said second means;
whereinsaid adaptive equalizer means is responsive to said first and second error signals; and said de-rotator means is responsive to one of said first and second error signals.
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13. In a system for processing a television signal, digital signal processing apparatus comprising:
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input means for receiving a multiple carrier composite PAM signal; signal conditioning means, including adaptive equalizer means, responsive to said composite signal for providing a conditioned composite signal at an output, said equalizer means including a single equalizing device having a wideband response encompassing more than one of said carriers and defined by one set of coefficients for equalizing said more than one carriers without separating said more than one carriers from the spectrum of said composite signal prior to equalization; means for deriving an error signal representing a condition of said PAM signal; and means for coupling said error signal to said signal conditioning means.
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14. In a system for processing a television signal, digital signal processing apparatus comprising:
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input means for receiving a composite multiple carrier PAM signal, said multiple carrier composite signal comprising a first carrier modulated by a first component, and a second carrier modulated by a second component; signal conditioning means including adaptive equalizer means exhibiting non-time-multiplexed operation and responsive to said composite signal for providing an equalized composite signal at an output, said equalizer means including a single equalizing device having a response encompassing said first and second modulated carriers for equalizing said first and second modulated carriers without separating said first and second modulated carriers from the spectrum of said composite signal prior to equalization; means for separating said first component and said second component of a conditioned composite signal from said conditioning means; first means responsive to separated data associated with said first component for producing corresponding output data; first detector means for producing a first error signal representing an offset between respectively corresponding input and output data of said first means; second means responsive to separated data associated with said second component for producing corresponding output data; second detector means for producing a second error signal representing an offset between respectively corresponding input and output data of said second means;
whereinsaid adaptive equalizer means is responsive to said first and second error signals.
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Specification