Frequency Mixer: 2 Inputs

Discussion in 'The Projects Forum' started by mauromj, Apr 2, 2014.

  1. mauromj

    Thread Starter New Member

    Oct 13, 2010
    3
    0
    Good evening all,

    I am working on a project that requires the mixing of 2 separate AC signals. I have done a lot of research and have not found any helpful information on how I can "add" these frequencies to produce a new frequency. For example, if I have an input1 of 5khz, and an input 2 of 1khz, I would (ideally) like an output of 6khz. I am not sure if this is possible or not. Even if this new output was not the sum, but simply the difference, multiplication, ect, I would be happy. Can someone please help as soon as possible?!

    Thanks!
     
  2. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,515
    1,246
    What you are describing is a mixer, or balanced mixer, or doubly balanced mixer. There are old circuits and new chips that do this, although usually it is done at radio frequencies. Do a search for "balanced mixer schematic" as a start.

    http://en.wikipedia.org/wiki/Frequency_mixer

    ak
     
  3. vk6zgo

    Active Member

    Jul 21, 2012
    677
    85
    Google for "double balanced mixers".
    These devices will give you quite a lot of cancellation of the input signals,but as 5kHz is quite close to 6kHz,you may still have a bit
    of a battle trying to suppress the unwanted signal.
     
  4. mauromj

    Thread Starter New Member

    Oct 13, 2010
    3
    0
    Ok thank you! I will do some research on a double balanced mixer. I have some requirements however. I will need to build one of these, instead of using a premade chip. I have op amps, fets, bjt's that I will need implement. Hopefully I can find some info out there using these. If any of you find any good information, I would appreciate the help. Thanks
     
  5. w2aew

    Member

    Jan 3, 2012
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    64
  6. MrChips

    Moderator

    Oct 2, 2009
    12,414
    3,353
    You need a multiply circuit. A transconductance amplifier or even a simple FET can do it.
     
  7. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
    1,222
    What you want to do is one of the core components in any lock-in amplifier. Here are some links
    https://cpm.uncc.edu/sites/cpm.uncc.edu/files/media/tn1000.pdf
    (note the appendix in this one)
    https://cpm.uncc.edu/sites/cpm.uncc.edu/files/media/tn1001.pdf
    https://cpm.uncc.edu/sites/cpm.uncc.edu/files/media/tn1002.pdf
    https://cpm.uncc.edu/sites/cpm.uncc.edu/files/media/tn1003.pdf
    There are many ways to do this. In your frequency range you can even use an analog multiplier IC. If you choose to use an analog approach. You should know that these most often do not work very well, then one of the input signals are very small compered to the other signal. What and why do you want to do this
     
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