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Modulate noise w/ LPF

Discussion in 'Electronic Design' started by Stuart Kendall, May 21, 2007.

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  1. I would like to modulate continuous white noise with an audio
    sinewave, by modulating the low pass cut-off of an in series active
    filter.

    Can anyone please advise me regarding the best practice for this? \

    The type of fliter most suited, how to feed the modulation signal,
    etc.

    Many thanks,

    Stuart Kendall
     
  2. Robert Baer

    Robert Baer Guest

    One *cannot* "modulate" with a linear device, period.
     
  3. D from BC

    D from BC Guest

    Voltage controlled LP filter??
    ssssssssswwwwwwwwwwWWWWWWWWW :)

    My guesses...
    switched capacitor filter IC
    program a PC sound card?
    music store effects rack/box
    ADC's, DAC and a DSP chip.
    Op amp active filter with opto conductors
    A capacitor,photoresister and a LED

    D from BC
     
  4. MooseFET

    MooseFET Guest

    Resistances that are near ground voltage and/or transconductances are
    the easiest to electronically control. If your control was digital,
    I'd suggest a DAC be used. There are some chips that do a multiply
    function.

    How good of a filter do you need this to be? How wide of a range does
    it need to be able to vary over?
     
  5. Tom Bruhns

    Tom Bruhns Guest

    What, exactly, is your definition of "modulate"? If not "modulate,"
    what WOULD you call what the OP wants to do? It seems to me that what
    he wants to do meets a reasonable definition of modulate: to change a
    characteristic of one signal under the control of another signal.
    He's suggesting to change the spectral content and the total energy of
    one signal, in response to another signal. Modulation. Period.

    Perhaps a filter with a signal input and a cutoff-frequency input is
    not a linear device...

    Cheers,
    Tom
     
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