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Direct conversion receiver with wide band analog frequency conversion front end and digital demodulating and selecting back end

  • US 6,334,051 B1
  • Filed: 03/04/1999
  • Issued: 12/25/2001
  • Est. Priority Date: 03/04/1998
  • Status: Expired due to Term
First Claim
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1. A receiver adaptable to a plurality of radio communication systems comprising:

  • a radio-frequency signal reception unit which collectively receives radio-frequency signals on a plurality of channels each of which is modulated with data;

    a quadrature demodulator which multiplies each of the radio-frequency signals by a first local signal to produce a first baseband signal, and multiplies each of the radio-frequency signals by a second local signal having a π

    /2-phase differs from the first local signal to produce a second baseband signal having a π

    /2-phase differs from the first baseband signal;

    a first low-pass filter which outputs a first low-frequency component signal from the first baseband signal;

    a second low-pass filter which outputs a second low-frequency component signal from the second baseband signal;

    a quadrature modulator which multiplies the first low-frequency component signal by a third local signal to produce a first intermediate-frequency signal, multiplies the second low-frequency component signal by a fourth local signal having a π

    /2-phase differs from the third local signal to produce a second intermediate-frequency signal, and combines the first intermediate-frequency signal and the second intermediate-frequency signal into an output signal;

    an A/D converter which converts the outputs signal into a digital signal;

    a digital downconverter which multiplies the digital signal by a first clock signal to produce a first digital baseband signal, multiplies the digital signal by a second clock signal having a π

    /2-phase differs from the first clock signal to produce a second digital baseband signal having a π

    /2-phase differs from the first baseband signal and selects a signal on at least one channel from the first digital baseband signal, selects a signal on at least one channel from the second digital baseband signal;

    a digital signal processing unit which processes the first digital baseband signal and second digital baseband signal to recover the data.

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