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PLL confusion

Discussion in 'Electronic Basics' started by jim, Nov 12, 2004.

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  1. peterken

    peterken Guest

    that's the idea yes, amplitude is on the vertical axis and phase is on the
    horizontal axis
    we're only comparing the horizontal axis, and (almost) ignoring the vertical
    unless to "select" a reference point

    the phase of a single signal has to do with the 360deg (2*pi rad) between
    two instances of a repetitive cycle
    whatever the amplitude, the 360deg is a given constant for every cycle of
    this signal
    whatever the time is to go through the full 360deg doesn't matter too, so
    ignore the aspect "time" too (disconnect "time" from "phase" for a moment in
    your mind)

    now, given the initial 5Hz and 10Hz of this thread, starting from a specific
    coinciding point of two signals (assume zero crossing) one can start
    counting the completed cycles as 360deg for every signal
    the 5Hz sig will have done 360deg after 1 cycle, whilst the 10Hz will be at
    720deg (= two cycles) at the finishing point of this first 5Hz cycle
    thus the phase difference of both signals will always increment, no matter
    how long you look at them (*unless* you take a new reference point and start
    counting from scratch but that's a new measurment)
    an integral part of a pll is a phase comparator (usually phase detector
    combined with an integrator) giving the "measure" for the phase difference
    to be able to adjust a vco which is another part of a pll
  2. jim

    jim Guest

    Got it now very grateful, all jim

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