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Gradually changing the phase of a signal

  1. Jul 27, 2012 #1
    Hello all.

    I have produced a square wave with a given frequency (period of about 0.5 seconds). I am trying to match the phase of the square wave with a periodic pulse of the same frequency. I can detect when I have acheved the phase difference between them of zero but I need a way to initially match up the phases.

    I was wondering if there is any way that I can let the phase of the square wave slowly drift untill I detect that they are in phase. An on/off signal to start and stop the drift would be ideal so that I could stop it drifting when required and let it drift again if they get out of sync.

    Thanks in advanced
  2. jcsd
  3. Jul 27, 2012 #2


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    Staff: Mentor

    How are you making the square wave now? Can you post the circuit?
  4. Jul 27, 2012 #3
    What you described sounds like a typical phase lock loop!!! You use the VCO to generate the square wave, then mix with the reference pulse and it will to generate the control voltage to control the frequency of the VCO. Look up Phase Lock Loop ( PLL) and see whether that helps.
    Last edited: Jul 27, 2012
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