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Delaying a signal 180 or 90 degrees

  1. Oct 30, 2015 #1


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    Gold Member

    How can I delay a sinusodial signal (voltage) 90 or 180 degrees?

    I have been thinking of a capacitor or an inductor in parallel with the voltage source but these components do not impact the phaseshift of the voltage but the current.

    Can anyone help me please?

    I know that there are other solutions to simple sinusodial signals like just inverting the signal but I am searching for a more complex solution.

    Sorry for my bad English.
  2. jcsd
  3. Oct 30, 2015 #2


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    Science Advisor

    The digital answer: Run the signal through an A/D converter, determine the period, do a digital delay, run it through a D/A converter.
  4. Nov 2, 2015 #3


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    Staff: Mentor

    That is correct: adding a capacitive load to a voltage source cannot affect the amplitude or phase of that source, with an ideal source.

    Filters are circuits which cause their output to be changed in both phase and amplitude, relative to their input. You could connect in series a few low-pass RC filter sections to get a combined delay of up to 180° at a given frequency. As a rule of thumb, work on 45° lag for each RC section. A consequence of this form of passive filter is that it attenuates the amplitude at the same time as providing a delay. Of course, different frequencies will undergo different delays, with any given circuit.

    There are filters which deliver a phase shift with almost no change in amplitude over a wide band; these can get complicated and to perform the feat demand precision components.
  5. Nov 2, 2015 #4


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    Science Advisor

    For example: https://en.wikipedia.org/wiki/All-pass_filter.
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