Phase Change

Discussion in 'The Projects Forum' started by roybalcombe, Jan 17, 2010.

  1. roybalcombe

    Thread Starter New Member

    Jan 17, 2010
    5
    0
    I am trying to build a sine wave generator with a frequency adjustment and amplitude adjustment then once set I want to progressively change the phase. I can find a circuit for the first part but how can I change the phase of a sine wave generator progressively through 360 degrees?
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    You will have to add more explanation to your need to change the phase. Phase relative to what? The oscillator must operate with a fixed phase relationship, or it will stop oscillating.
     
  3. roybalcombe

    Thread Starter New Member

    Jan 17, 2010
    5
    0
    Progressively advance or retard the phase to get match with base frequency on the scope
     
  4. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
    1,222
    Is that all, or is it part of some application.?
     
  5. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
    1,222
    It is a technology named phase-locked loop or phase lock loop (PLL). I have never used it. But you may Google the term.
     
  6. roybalcombe

    Thread Starter New Member

    Jan 17, 2010
    5
    0
    The application is to find the phase of a natural oscillation where the frequency and amplitude can be determined but the phase cannot. By progressively changing the frequency the point of cancellation will indicate 180 out of phase.
     
  7. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
    1,222
    It is a design element named allpass filter. It may do some of what you want. Use Google for more info
     
  8. roybalcombe

    Thread Starter New Member

    Jan 17, 2010
    5
    0
    Yes that looks like a good lead. Thanks
     
  9. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    A few decades ago, I did this for a color background generator for broadcast television. One thing that made it easy was that the design only had to work on the NTSC color frequency 3.59MHz. The circuit was basically an analog computer that solved the trigonometric equation sin(ωt +θ) = Cos(ωt)Sin(θ) + Sin(ωt)Cos(θ). I generated Sin(θ) and Cos(θ) from a sin-cosine potentiometer and I designed a circuit that created the 3.59MHz and the same frequency shifted by 90 degrees. I then fed these signals into a couple of four-quadrant analog multiplier ICs and then summed the outputs from the two mulitpliers to produce the final result. It worked very well.

    hgmjr
     
  10. kubeek

    AAC Fanatic!

    Sep 20, 2005
    4,670
    804
    As beenthere said, phase relative to what? Do you mean to create an oscillator with two outputs, where one is shifted by some phase from the other?

    Isn´t that what trigger and trigger delay is for?
     
  11. atferrari

    AAC Fanatic!

    Jan 6, 2004
    2,651
    766
    The post suggests that the OP would hardly know what are these.
     
  12. roybalcombe

    Thread Starter New Member

    Jan 17, 2010
    5
    0
    Using the scope would only be to test that the circuit can change frequency, amplitude and then progressively change the phasing. In the application in the medical field it would only be the patient that could know when the phase was 180 out of phase by the cancellation response. The phase cannot be detected directly.
     
  13. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
    1,222
    Can you elaborate more on what you are trying to do. What kind of medical application is this.
     
  14. kubeek

    AAC Fanatic!

    Sep 20, 2005
    4,670
    804
    Let me ask once again, out of phase with what? To be able to talk about phase, you need to have TWO signals. So what is the second one?

    Unless you are able to explain us what youre actually trying to do, there is little point discussing it any further.
     
Loading...