Demodulation( Envelope Detector)

Discussion in 'General Electronics Chat' started by vincent19-mas, May 23, 2013.

  1. vincent19-mas

    Thread Starter Member

    Dec 27, 2012
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  2. Dodgydave

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    Jun 22, 2012
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    The germanium diode half wave rectifies the incoming signal, and the capacitor/resistor filter out the rf and smooth out the recovered signal.
     
  3. vincent19-mas

    Thread Starter Member

    Dec 27, 2012
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    Ay detail explanation about all these ?

    Thanks !
     
  4. crutschow

    Expert

    Mar 14, 2008
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    The AM modulation produces an RF waveform that varies in amplitude in response to the amplitude. The diode rectifies the RF to produce a half-wave of the RF which has an average value equal to the modulation signal. The RC filter removes the RF, leaving the signal that originally modulated the radio wave.
     
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  5. vincent19-mas

    Thread Starter Member

    Dec 27, 2012
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    Hey guys, normally what will the questions been asked for the modulating and demoudlting circuit ?

    I am so confused now..LOL
     
  6. crutschow

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    So this is homework for a quiz?
     
  7. vincent19-mas

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    Dec 27, 2012
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    Nope.. This is like a presentation :) I need some help in this :(

    Appreciate your help

    Thanks !
     
  8. crutschow

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  9. vincent19-mas

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    Dec 27, 2012
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    Yes, so I wonder what would the instructor ask probably :)
     
  10. crutschow

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    Likely questions to determine if you understand the basic of AM modulation and demodulation. Do you?
     
  11. vincent19-mas

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    Dec 27, 2012
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    Not really fully understand yet ..Sigh.
     
  12. crutschow

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    If you have specific questions, perhaps we can help.
     
  13. vincent19-mas

    Thread Starter Member

    Dec 27, 2012
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    how the resistor and capacitor discharge and change ?

    I am not really understand fully yet about functions of every components in envelope detector. :(

    Thanks :)
     
  14. crutschow

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    If you don't understand the operation of resistors and capacitors then we are really starting at the beginning.

    Try reading this and this.
     
  15. vincent19-mas

    Thread Starter Member

    Dec 27, 2012
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    HAHAHA, well, I know the basic function of both components. Just that I am not so sure how it works in this circuit . How/ when it discharge and charge ?

    Thanks
     
  16. bertus

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    Apr 5, 2008
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  17. vincent19-mas

    Thread Starter Member

    Dec 27, 2012
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    Wow, that pretty good pdf. Anyway, what does it means by distortion ? It might be asked by instructor. I may say the facts that if RC is not correct, distortion will occrus. But well how is it ?

    Thanks :)
     
  18. vincent19-mas

    Thread Starter Member

    Dec 27, 2012
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    Hey, based on the picture, what does it means by creating a baseband signal ?

    I dont get it. I understand that baseband filter is a filter that will not filter a specific range of frequency.

    Thanks :)
     
  19. vincent19-mas

    Thread Starter Member

    Dec 27, 2012
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  20. crutschow

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    The function of a low pass filter is to pass low frequencies and attenuate frequencies above the filter's corner frequency.

    In this case the LP filter is used to attenuate the RF frequency but pass the modulation frequency.

    Note that a standard op amp will not work very well as a filter here because of the op amps limited frequency response. An active filter requires the op amp to have significant gain at the RF frequency and a standard op amp doesn't. Better to use just a passive RC LP filter.
     
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