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AM digital demodulator

  • US 4,857,859 A
  • Filed: 06/17/1988
  • Issued: 08/15/1989
  • Est. Priority Date: 06/18/1987
  • Status: Expired due to Term
First Claim
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1. An AM demodulator of a digital signal processing type wherein an analog AM signal is converted to a digital AM signal, the digital AM signal is squared and a one sample-delayed version of the digital AM signal is squared, these squared signals are added, and the square root of the resulting sum of the squared signals is extracted as an AM demodulated signal, comprising:

  • a level detector for detecting the level of a sum signal representing the sum of the squared signals;

    an upward bit shifter for bit shifting upwardly the sum signal on the basis of the output from the level detector to correct the level of the sum signal;

    a polynomial calculator for approximately extracting the square root of the level corrected sum signal; and

    a downward bit shifter for bit shifting downwardly the output signal from the polynomial calculator to correct the level of the just mentioned output signal.

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