signals addition

Discussion in 'General Electronics Chat' started by joni, Dec 5, 2009.

  1. joni

    Thread Starter Member

    Oct 4, 2009
    39
    0
    what is mixer diode ?
    who it work ?
     
  2. S_lannan

    Active Member

    Jun 20, 2007
    247
    2
  3. joni

    Thread Starter Member

    Oct 4, 2009
    39
    0
    This link is first appear in google when you search after "mixer diode"
    This is the first thing that I do
    I search after other information about mixer diode
    Or I will glad if anybody here know what is mixer diode
    Will write in short what is it?
     
  4. S_lannan

    Active Member

    Jun 20, 2007
    247
    2
    A mixer diode is not really any majorly specific type of diode. It is really called that because it is used in a mixing circuit.

    Here is a link that explains a bit about mixers
    http://en.wikipedia.org/wiki/Frequency_mixer

    To perform the frequency mixing function you need a non linear device, a very simple and cheap non linear device is a diode.

    I have done a few simulations with two sources, a 1MHz signal and a 50KHz signal. The circuit achieves amplitude modulation with the 1MHz carrier and 50KHz intelligence signal.

    I mix them together through linear and non linear networks and display the output on a spectrum analyser.

    The first image is the output of the linear circuit without the mixing diode. The two original frequences are the only ones on the analyser.

    The second image shows the output of the non linear circuit with the mixing diode in the circuit.
    Here you can see two new frequencies on the spectrum analyser
    950KHz and 1050KHz.

    The third circuit uses a tank for selectivity of frequencies, only the side bands and carrier pass. The baseband signal is no longer present.


    This may / may not have helped. You do need to understand a bit of RF theory to understand these circuits / devices.
     
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