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Demodulator for multiphase PSK or multilevel QAM signals

  • US 4,620,159 A
  • Filed: 08/27/1985
  • Issued: 10/28/1986
  • Est. Priority Date: 08/27/1984
  • Status: Expired due to Term
First Claim
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1. A demodulation device comprising:

  • phase detector means for demodulating a multiphase PSK carrier wave or a multilevel QAM wave into a baseband signal;

    A/D converter means for sampling the output signal of said phase detector means in response to a timing signal and converting it to digital signals;

    means responsive to said digital signals from said A/D converter means for supplying a carrier wave to said phase detector means;

    timing synchronizing means for generating a timing signal representing a timing of sampling of said A/D converter means, and timing synchronizing means having a timing signal generator, a phase of which is controlled by a predetermined phase control signal, which generates the timing signal, and which includes a low-pass filter and a voltage controlled oscillator adapted to receive the output from said filter and to provide an output in at least a loop with a loop parameter, a polarity identification circuit for receiving a first predetermined signal among said digital signals from said A/D converter means, identifying a polarity of a differential coefficient of the baseband signal at a sampling point of said A/D converter means and generating a polarity identification signal, and logic circuit means for receiving and processing according to a predetermined logic the polarity identification signal from said polarity identification circuit and a second predetermined signal among said digital signals from said A/D converter means and generating and supplying to said timing signal generator a phase control signal representing a deviation of an actual sampling point of the baseband signal from an optimal sampling point; and

    carrier asynchronism detecting means for detecting an asynchronism state of said carrier wave supplying means and supplying to said timing synchronizing means a signal which controls said loop parameter of said timing synchronizing means.

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