need help in this circuit - Zero Bias Schottky Detector

Discussion in 'The Projects Forum' started by harikanaidu, Feb 17, 2016.

  1. harikanaidu

    Thread Starter Member

    Nov 28, 2014
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    rf detetctor.jpg
    Can any one explain how this circuit detects RF signals
     
  2. harikanaidu

    Thread Starter Member

    Nov 28, 2014
    76
    1
    what is exactly the fuction of this circuit?
     
  3. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Looks like it detects by diode rectification of the RF waveform

    Google that term...it is mainly for AM modulation.
     
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Its an AM detection circuit, the diode is a half wave rectifier and the RC filter removes the carrier, so the result is the original modulation audio.
     
  5. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    The word "detect" used here does not mean what you think. It is not determining the presence or absence of a signal. In radio, a detector is a circuit that extracts the modulated signal (audio, video, whatever) from the carrier wave. The schematic shows a basic AM (amplitude modulation) detector.

    ak
     
  6. harikanaidu

    Thread Starter Member

    Nov 28, 2014
    76
    1
    Mobile-Phone-Detector-Circuit-Diagram.jpg
    May i know how this circuit is detecting the mobiles then?
     
  7. crutschow

    Expert

    Mar 14, 2008
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    My company used a similar circuit to detect the level of microwave radiometer signals on an earth orbit weather satellite except it used back (tunnel) diodes, instead of Schottkys, for better sensitivity.
    Basically it generated a slowly varying DC level ( a few hundred Hz) in proportion to the intensity of the black body radiation in the microwave spectrum from earth.
     
  8. harikanaidu

    Thread Starter Member

    Nov 28, 2014
    76
    1
    How it is used to detect the mobile signals
     
  9. Ramussons

    Active Member

    May 3, 2013
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    If there's a RF input, you will get a DC output.

    If you have a good tuned filter at the input, you can detect a transmission over a particular radio spectrum.

    Else, you can get DC even from random RF signals, like a motorbike passing by .....
     
  10. DickCappels

    Moderator

    Aug 21, 2008
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  11. alfacliff

    Well-Known Member

    Dec 13, 2013
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    actually, schotkey diodes have a higher minimum rf voltage for detecion than the older germanium diodes. if you apply a little bias to them, they will detect down to almost zero volts.
     
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