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How to measure phase difference of 2 signals using IQ demodulator

  1. Sep 13, 2011 #1
    for one section of my project, i need to know the phase difference between two signal.
    they are both 40MHz, but out of phase by a certain angle.

    i have a AD8333 board from Analog Devices,
    it is a dual I/Q demodulator consist of double-balanced gilbert cell mixers.

    The board has 2 RF inputs, a LO input, and 4 output (I1, I2, Q1, Q2).

    I have an oscilloscope to display the results.

    according to wikipedia http://en.wikipedia.org/wiki/Phase_detector#Analog_phase_detector
    there is a way to measure the phase difference using IQ demoludator.

    in this post, https://www.physicsforums.com/showthread.php?t=336619
    f95toli mentioned that:
    the magnitude is just given by the norm (sqrt(I^2+Q^2)) and the phase by the phase angle (arctan I/Q)

    So is this method bellow correct?
    to get the phase difference of both my RF signal,
    i put one the signal into RF input1, and the second signal into the LO,
    then i display both the I1, and Q1 in the oscilloscope, and get an get the peak to peak magniture for both the I1 and Q1, then calculate arctan I1/Q1, to get the phase difference?
  2. jcsd
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