exor output

Discussion in 'General Electronics Chat' started by matbymay, Aug 16, 2009.

  1. matbymay

    Thread Starter Member

    Jul 14, 2009
    27
    0
    hi everbody

    consider i have two 100khz waves and there is phase differences between them. i would like to measure phase differences using exor. but how can i get voltage or analog value from output of exor.

    thank you
     
  2. eblc1388

    Senior Member

    Nov 28, 2008
    1,542
    102
    The output of the XOR would be a variable duty cycle pulse depending upon the phase difference. You fed this into a simple RC filer and get back a DC voltage proportional to the pulse width.

    The actual values of R and C time constant depends on how fast the two signal phases are moving.
     
  3. bertus

    Administrator

    Apr 5, 2008
    15,647
    2,346
    Hello,

    Take a look at the CD4046 PLL IC.
    (see datasheet).
    That has two types of phase comparators in it.

    Greetings,
    Bertus
     
  4. matbymay

    Thread Starter Member

    Jul 14, 2009
    27
    0
    thank you bertus

    i have cd4046 pll it is ok actually i havent tried yet. but i need diffenrence technics to get gc value. yes low pass filter is good idea and output of exor data cycle app. 10 -100 usn. so what do you think that time too much to give reasonable dc value ?
     
  5. matbymay

    Thread Starter Member

    Jul 14, 2009
    27
    0
    thank you eblc1388
    any different ideas?
     
  6. bertus

    Administrator

    Apr 5, 2008
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    2,346
    Hello,

    Sorry but what is the gc value?
    The 4046 has two phase comparators.
    An EXOR and a kind of charge-pump.
    How fast is the phase of the 100 kHz changing?

    Greetings,
    Bertus
     
  7. matbymay

    Thread Starter Member

    Jul 14, 2009
    27
    0
    how fast? you mean phase differences or delay time i didnt get. could you explain please
    sorry it would be dc value
    thank you
     
  8. matbymay

    Thread Starter Member

    Jul 14, 2009
    27
    0
    dc value or analog value ac maybe it shold be analog which is easy to get from output of exor of course it is digital but how can i convert to digital to analog. digital analog converter maybe you can suggest me ?
     
  9. bertus

    Administrator

    Apr 5, 2008
    15,647
    2,346
    Hello,

    Did you have a look at table 4 of the datasheet?

    [​IMG]

    It shows the difference between the two comparators and use of RC filters.
    The RC filter is needed to convert the phase info to DC.

    Greetings,
    Bertus
     
  10. matbymay

    Thread Starter Member

    Jul 14, 2009
    27
    0
    so should i look at frequency capture range and loop filter component selection on table 4?
    another question is that i will connected inputs which are measured and power for IC. do i need to connect vco or something like that? i just want to use exor.

    thank you
     
  11. bertus

    Administrator

    Apr 5, 2008
    15,647
    2,346
    Hello,

    If you just want the XOR function, you can also take a CD4030.
    That contains 4 XOR's.

    Greetings,
    Bertus
     
  12. matbymay

    Thread Starter Member

    Jul 14, 2009
    27
    0
    thanks bertus you r very helpfull
    so i can use c4030 ic for measure phase diff. and with low pass filter( with time constant ) i will get analog value

    do you know any other technics to measure phase differences ?
     
  13. bertus

    Administrator

    Apr 5, 2008
    15,647
    2,346
    Hello,

    If you know the repetition time, in your case 1 / 100 kHz = 10 μS, there is the following method.
    Start a counter with the up going signal from 1 and stop it with the upgoing signal from 2.
    The time difference will be a measure of the phase difference.
    The higher the frequqncy of the counter the more precize you can measure the phase.
    If you take a frequency for the counter that is 360 times higher than the frequency of the phse signals the counter will give an anwer in degrees.

    Greetings,
    Bertus
     
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