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Synchrodyning of VSB and QAM final I-F signals supplied by separate converters in a QAM/VSB digital TV receiver

  • US 6,104,763 A
  • Filed: 01/13/1999
  • Issued: 08/15/2000
  • Est. Priority Date: 02/20/1998
  • Status: Expired due to Fees
First Claim
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1. A radio receiver for receiving a selected digital television signal, irrespective of whether it is a quadrature-amplitude-modulation (QAM) or a vestigial-sideband (VSB) digital television signal, said radio receiver comprising:

  • front-end circuitry for selecting said selected digital television signal and converting it with amplification to at least a first amplified penultimate intermediate-frequency signal;

    a first frequency converter for converting to a first final intermediate-frequency signal said first amplified penultimate intermediate-frequency signal, said first frequency converter includinga first controlled oscillator the frequency and phase of its oscillations controlled by a first automatic-frequency-and-phase-control signal;

    a first analog-to-digital converter for digitizing said first final intermediate-frequency signal to generate a digitized first final intermediate-frequency signal;

    circuitry for synchrodyning any QAM digital television signal in said digitized first final intermediate-frequency signal to baseband, thus to generate a first in-phase baseband signal and a first quadrature-phase baseband signal;

    circuitry for synchrodyning any VSB digital television signal in a digitized second final intermediate-frequency signal to baseband, thus to generate a second in-phase baseband signal and a second quadrature-phase baseband signal;

    first automatic-frequency-and-phase-control circuitry for generating said first automatic-frequency-and-phase-control signal responsive to said first in-phase baseband signal and said first quadrature-phase baseband signal, said first automatic-frequency-and-phase-control signal being responsive neither to said second in-phase baseband signal nor to said second quadrature-phase baseband signal;

    a second frequency converter for converting to a second final intermediate-frequency signal a second amplified penultimate intermediate-frequency signal supplied from said front-end circuitry, said second frequency converter includinga second controlled oscillator the frequency and phase of its oscillations controlled by a second automatic-frequency-and-phase-control signal;

    a second analog-to-digital converter for digitizing said second final intermediate-frequency signal to generate a digitized second final intermediate-frequency signal;

    second automatic-frequency-and-phase-control circuitry for generating said second automatic-frequency-and-phase-control signal responsive to said second quadrature-phase baseband signal, said second automatic-frequency-and-phase-control signal being responsive neither to said first in-phase baseband signal nor to said first quadrature-phase baseband signal.

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