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Receiving circuit for demodulating an angle modulated signal

  • US 5,260,671 A
  • Filed: 05/15/1992
  • Issued: 11/09/1993
  • Est. Priority Date: 05/17/1991
  • Status: Expired due to Fees
First Claim
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1. A receiving circuit for receiving a suppressed carrier input signal, comprising:

  • coherent detecting means for coherently detecting said suppressed carrier input signal;

    voltage controlled oscillating means for oscillating to said coherent detecting means as a recovered carrier;

    phase error detecting means for detecting a phase error signal between said suppressed carrier input signal and said recovered carrier, wherein said voltage controlled oscillating means is controlled by said phase error signal;

    synchronous state detecting means for detecting whether a carrier recovery phase locked loop circuit is in synchronous or asynchronous states, said carrier recovery phase locked loop including said coherent detecting means, said voltage controlled oscillating means and said phase error detecting means; and

    controlling means for controlling said voltage controlled oscillating means depending on a low-frequency component level of said phase error signal, so that an operating point of said carrier recovery phase locked loop circuit moves toward the center when an output of said synchronous state detecting means indicates that said carrier recovery phase locked loop is in the asynchronous state.

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