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Efficient digital frequency division multiplexed signal receiver

  • US 5,058,107 A
  • Filed: 01/05/1989
  • Issued: 10/15/1991
  • Est. Priority Date: 01/05/1989
  • Status: Expired due to Term
First Claim
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1. A frequency division multiplex receiver for isolating a frequency division multiplex channel contained within a predetermined frequency division multiplex (FDM) band, comprising:

  • an RF amplifier;

    an RF bandpass anti-alias filter having a pass-band for passing substantially the entire predetermined FDM band and having a skirt width Ftrans, said passband including frequencies above a sample frequency Fs at which the output of the filter is sampled;

    analog-to-digital conversion means for sampling the analog output of said anti-alias filter to provide an aliased frequency down converted digital version of the received frequency division multiplexed electromagnetic signals within the predetermined frequency division multiplex band, said analog to digital conversion means having a sample rate Fs that is less than the lowest frequency in the predetermined FDM band and is equal to 4NFBW +FL, where FBW is the bandwidth of the predetermined FDM band, N is equal to 1, and FL is the lower band edge of the aliased image resulting from the digital conversion sampling process and is subject to the following limits relative to the skirt width Ftrans of the bandpass anti-alias filter;

    
    
    space="preserve" listing-type="equation">1/2F.sub.trans ≦

    F.sub.L ≦

    1/2F.sub.s -(F.sub.BW +1/2F.sub.trans) whereby the output of the analog to digital conversion means includes a non-distorted aliased image of the predetermined frequency division multiplex band;

    a gain controlled amplifier responsive to the output of said analog to digital conversion mean for controlling the gain of the analog received RF signal provided to said analog to digital conversion means;

    digital complex frequency translation means for frequency translating said aliased frequency down converted digital signal to provide a frequency translated digital signal having the center of the selected channel at zero frequency; and

    means for filtering said translated sampled digital received signal to isolate said selected channel.

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