Split carry wave

Discussion in 'Wireless & RF Design' started by phongkem, Mar 17, 2015.

  1. phongkem

    Thread Starter New Member

    Nov 19, 2011
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    0
    Hello everybody,
    I'm trying to get carry wave from signal in the picture. It's 2 different frequency sin signals mixed together. Could you please give me some advice.
    Thanks and best regards.
     
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Looks like you have the sum of two sines?

    177.jpg
     
  3. alfacliff

    Well-Known Member

    Dec 13, 2013
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    it looks like you are viewing a on air signal from a digital tv station. it takes more than just a few bandpass filters to seperate out the individual signals on the carrier.
     
  4. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    at 10ms per div????
     
  5. alfacliff

    Well-Known Member

    Dec 13, 2013
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    what does the vertical deflection setting have to do with it? if you check the frequency, 56.70, thats channel 2 tv chanel.the horizontal rate is low enough that it shows the individual data chanels on the tv chanel. if you had a spectrum analyzer, the signal would look like a haystack, lots of carriers, each with data. not too sure what the horizontal low frequency componant is, might be hum.
     
  6. vk6zgo

    Active Member

    Jul 21, 2012
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    I think you may have found one of the limitations of an inexpensive DSO.
    It looks a lot like "aliasing"to me.
    If you look at a higher frequency signal at a very long time/div setting.the DSO will in many cases reduce its sample rate below,or very close to the frequency of the observed signal
     
  7. DickCappels

    Moderator

    Aug 21, 2008
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    You have the two signal sources in series so all you can get is the sum of the two signals. To see the modulated envelope you need to multiply one signal by the other. That can be done many ways.

    A small tweak of your circuit will get you some sort of an envelope (not pretty), if your scope has an FFT function you should be able to see sidebands. You might want to follow the mixer with a high pass filter to remove the baseband signal.
    [​IMG]
     
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