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Wide band zero if quadrature demodulator using a intermediate frequency and a single local oscillator

  • US 5,761,615 A
  • Filed: 05/31/1995
  • Issued: 06/02/1998
  • Est. Priority Date: 05/31/1995
  • Status: Expired due to Term
First Claim
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1. A low power zero-IF selective call receiver, comprising:

  • a local oscillator that generates an injection signal at a first frequency (fLO);

    a first mixer coupled to the local oscillator for converting a received carrier signal of a second frequency (fC) to an intermediate signal of a third frequency (fIF) in response to the injection signal at the first frequency (fLO), where the third frequency (fIF) associated with the intermediate signal is one of a sum or a difference of the first (fLO) and second (fC) frequencies;

    a digital phase shifter/divider coupled to the local oscillator and to the first mixer, the digital phase shifter/divider generating a pair of quadrature phase related injection signals at the third frequency (fIF) which is the first frequency (fLO) divided by an integer greater than 1;

    a pair of second mixers coupled to the digital phase shifter/divider and the first mixer, the pair of second mixers converting an in phase component of the intermediate signal to an in phase baseband signal and a quadrature component of the intermediate signal to a quadrature baseband signal in response to an in phase and quadrature component of the pair of quadrature phase related injection signals, respectively.

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