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IF frequency qu

Discussion in 'Electronic Design' started by thejim, Feb 6, 2006.

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  1. thejim

    thejim Guest

    I know that IF frequency is the difference between the incoming signal
    and the local oscilator frequency in a frequency synthesizer. My
    question is why in a frequency synthesizer we need the IF frequency>
     
  2. For a simple approach, you don't need IF. You
    may be able to generate the RF directly when
    the VCO is able to do so.

    Rene
     
  3. Tim Wescott

    Tim Wescott Guest

    A synthesizer doesn't need an IF ("IF frequency" is redundant -- "IF"
    stands for "Intermediate Frequency").

    Some multi-loop synthesizers have an IF sort of thing, but by no means all.

    What is the context? What raised the question in your mind?
     
  4. Because in a tuner you need to select a particular frequency for
    amplification and detection. You could do this with a very sharp
    variable-frequency bandpass filter, but this is expensive and unstable.
    Instead you use a very sharp FIXED-frequency bandpass filter on the IF.
    This also has the advantage of avoiding feedback from the tuner back to
    it's antenna - the input and output frequencies from the mixer are
    completely different.
     
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