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RF Mixers

Discussion in 'Electronic Basics' started by Don, Jul 22, 2003.

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  1. Don

    Don Guest

    Does anyone know of a web page that describes the purpose and
    operation of RF mixers? Best I have been able to tell that given two
    frequencies, a mixer generates the sum and difference.


  2. A E

    A E Guest

    Yes, that's right. Check here for some more fun:
    and scroll down some.
  3. dB

    dB Guest

  4. There was an article in Circuit Cellar 2-3 months ago...
    You can also find a good application note on
    (describing more the parameters of mixers)


    Robert Lacoste - ALCIOM : The mixed signals experts
  5. Precious Pup

    Precious Pup Guest

    Others have some pointers. Try Synergy Microwave too. They have some app notes.

    Mixers, RF or otherwise, are schematically represented by an X. *The X literally means multiplication*. That
    is, multiplication in the time domain (or convolution in the frequency domain).

    For example, you have 2 sinusoids applied to the two "input" ports of a mixer (for some passive mixers I's and
    O's are interchangable).

    x1(t) = cos(w1·t)
    x2(t) = cos(w2·t)

    So the mixer literally does:

    mixer_out = x1(t)·x2(t) = cos(w1·t)·cos(w2·t)

    and by trig identity, we then have

    x1(t)·x2(t) = 0.5·cos([w1-w2]·t) + 0.5·cos([w1+w2]·t)

    So there you see the mathematical result explaining "sum and difference" frequencies. There is usually a
    little more to it on account of the fact that RF mixers often have one of the ports "overdriven" or run in the
    "switch mode" (the "LO" port). See the links.
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