Patent ID: 6512555
Filing Date: 2003-01-28
Classification: H03D,H04B,H04L,H04N

Abstract:
Apparatus for reproducing data transmitted by amplitude-modulation of a carrier by multi-level symbol code sequences, said apparatus comprising:a tuner, for selecting said carrier amplitude-modulated by multi-level symbol code sequences and converting the frequencies thereof to generate a final intermediate-frequency signal, said tuner including a local oscillator for supplying local oscillations used in converting the frequencies of said carrier amplitude-modulated by multi-level symbol code sequences, said local oscillations being of a frequency and phase that is controlled in response to an automatic-frequency-and-phase-control signal applied to said local oscillator; a sample clock generator for generating sample clock signals; an analog-to-digital converter for digitizing samples of said final intermediate-frequency signal taken in response to said sample clock signals, thereby to generate samples of a digitized final intermediate-frequency signal; digital synchrodyning circuitry responsive to said digitized final intermediate-frequency signal for generating a digital in-phase baseband signal and a digital quadrature-phase baseband signal, by synchrodyning said digitized final intermediate-frequency signal to baseband; circuitry for generating a lowpass filter response to said digital quadrature-phase baseband signal, which said lowpass filter response is applied to said local oscillator as said automatic frequency and phase control signal, thereby completing a feedback loop that adjusts said local oscillations for causing said digital in-phase baseband signal to be descriptive of transmitted multi-level symbol code; and symbol decoding circuitry, responsive to said multi-level symbol code sequences as reproduced in said digital in-phase baseband signal, for reproducing the transmitted data.