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Simple Frequency Scaler and Phase Shifter

Discussion in 'Electronic Design' started by [email protected], May 16, 2007.

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  1. Guest

    I am working on a little hobby project over the summer, and I need
    some sort of non-integer Frequency Scaler (or Counter) and a Phase
    Shifter. Unfortunately I don't know of any easy way to do what I need
    to do, and could use some general advice to figure out the best way to
    handle it.

    The input signal would likely be less than 500hz, either Square-wave
    or Sine-wave (I can easily generate either). I am looking for the
    ability to scale the input signal over the full scale of Plus or Minus
    ~10%, and would like to be able to phase shift the signal a full 180
    degrees in either direction. The output signal can also be either
    Square-wave or Sine-Wave. The key feature I'm looking for here is
    stability: I don't really care how accurate or linear the circuit res
    ponce is, but ideally I want the output signal to be as stable as

    For the Frequency Scaler I have been looking at a Frequency-To-Voltage
    Converter, Voltage adder, Voltage-To-Frequency Converter
    configuration. Unfortunate all of the converters I've been looking at
    don't seem to be very happy at such low frequencies. There is also the
    problem of maintaining calibration between the two converters.

    The Phase Shifter has proven to be significantly more difficult. The
    only idea I've managed to come up with so far is to feed a square-wave
    input signal into an integrator, then trigger a new square-wave off
    the triangle-wave that comes out of the integrator. While I think this
    should work, there has got to be a better way.

    I would greatly appreciate any ideas or suggestions.


  2. D from BC

    D from BC Guest

    I barely remember the crappy digital phase shifter I made 10 years
    I used two 555 timers and a dual pot.
    D from BC
  3. Phil Allison

    Phil Allison Guest


    ** Sun stroked Groper Alert !

    ** The +/-10% frequency variation can be done with a "digital pitch
    shifter" - buy one at any music shop that sells electric guitars and
    accessories. Or pick one up on Ebay, of course.

    Once the pitch of a signal has been shifted this way - no phase
    relationship with the original is left.

    ......... Phil
  4. MooseFET

    MooseFET Guest

    One way to do it is to have sin() and cos() outputs on your generator
    and two pots to give each a gain from -1.0 to +1.0

    Do you need to add a frequency or multiply the frequency by some

    Imagine the pots of the above suggestion were varied so that the phase
    was constantly advanced with time. This would give the adding of a
    frequency. A couple more sin() and cos() signals driving a multiplier
    or fader circuit would do it.

    You can also use a PLL like the HC4046 to multiply the signal way up
    in frequency and then divide it down by a slightly different factor.

    The other solution is the classic "use a PIC" sort of answer. A PIC
    can measure the period of a signal on its input and make one with a
    different period on its output.
  5. MooseFET

    MooseFET Guest

    In -+-/\/\---+----/\/\----
    ! ! !
    ! --!-\ !
    ! POT ! >------+---- Out
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