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Zero IF receiver employing, in quadrature related signal paths, amplifiers having substantially sinh.sup.-1 transfer characteristics

  • US 5,159,710 A
  • Filed: 10/25/1991
  • Issued: 10/27/1992
  • Est. Priority Date: 06/17/1988
  • Status: Expired due to Fees
First Claim
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1. A zero IF receiver comprising an input terminal for an input signal having a frequency proximate a center frequency, means coupled to the input terminal for down-converting said input signal in frequency relative to said center frequency to produce down-converted in-phase and quadrature-phase signals, first and second amplifiers fed by said down-converting means and having a substantially sin h-1 transfer characteristic, the in-phase and quadrature-phase signals produced by said down-converting means being applied to said first and second amplifiers, respectively, which produce first and second output signals corresponding substantially to the logarithm of the in-phase and quadrature-phase signals, and demodulating means, said demodulating means comprising means for determining an indication of amplitude of the input signal by selecting, as an estimate of the amplitude of the input signal within 3 db of the correct value, that one of the first and second output signals having the larger signal absolute value and means for deriving an indication of phase angle of the input signal from the difference between the first and second output signals.

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