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Qpsk demodulator

  • US 4,769,816 A
  • Filed: 11/08/1985
  • Issued: 09/06/1988
  • Est. Priority Date: 11/08/1985
  • Status: Expired due to Fees
First Claim
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1. In a communication system wherein time-multiplexed phase shift keyed (PSK) signals at a radio frequency from a single transmitting station are received at each one of a plurality of spatially separated receiving stations, such transmitted signals having a preamble portion followed by a data bearing portion, each one of the plurality of spatially separated receiving stations having a receiver, each one of such receivers having an improved demodulator adapted to demodulate the preamble and data portion of the received PSK signals and to synchronize to the preamble portion of the received PSK signals, each one of such improved demodulators comprising:

  • means for demodulating the received PSK signals to baseband PSK signals;

    sampling means for sampling the received PSK signals at a sampling rate at least the same as the symbol rate of the received PSK signals;

    indicator means, responsive to the sampled baseband PSK signals, for generating a correlation signal proportional to the degree of correlation between the amplitude of the baseband PSK signals and a predetermined optimal amplitude;

    first clock means for generating dither clock pulses, the dither clock pulses applied to the sampling means to vary the sampling rate; and

    correction means, responsive to the correlation signal and the dither clock pulses, for generating an error signal for application to the sampling means to vary the sampling rate until variations in the correlation signal are minimized.

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