what is a LOG sweep ?

Discussion in 'Math' started by andrewmm, Feb 25, 2011.

  1. andrewmm

    Thread Starter Member

    Feb 25, 2011
    29
    6
    Hi

    A real simple question that has puzzled me too long.

    In terms of a phase accumulator.

    a constant frequency out Fout , is a constant phase increment,

    New phase = old phase + phase constant


    For a linear up sweep of Fout

    new Phase = old phase + ( phase constant * N)

    where N is an integer, increases by 1 on each iteration


    So for a log sweep ?

    new phase = old phase + ( ??? )



    so what do I put in for ???
     
  2. someonesdad

    Senior Member

    Jul 7, 2009
    1,585
    141
    I can't speak authoritatively within the context you've given, but "log sweep" generally means that the logarithm of the parameter changes linearly.
     
  3. Georacer

    Moderator

    Nov 25, 2009
    5,142
    1,266
    So instead of increasing by 1 in every iteration, N' will be
    N'=e*N.
    Sounds reasonable.
     
  4. andrewmm

    Thread Starter Member

    Feb 25, 2011
    29
    6
    Thanks

    can i turn the question around ?

    If for instance I have a plot of a 'log sweep',
    how could I 'prove' that it is a log sweep ?
    how could I prove the parameters of the 'plot' ?
    like ( start freq , stop freq, sweep 'speed' )

    for a sweep down, would it be like constant number of cycles per octive ? or decade or something ?

    My current best bet is to generate a plot algorithmically, then compare the points !
     
  5. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,777
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  6. andrewmm

    Thread Starter Member

    Feb 25, 2011
    29
    6
    would you consider a plot as sufficient,
     
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