introduce jitter in cadence PLEASE HELP

Discussion in 'General Electronics Chat' started by farid82, Jan 18, 2012.

  1. farid82

    Thread Starter New Member

    Jan 15, 2012
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    0
    Hi folks,

    for a project I*m working I need a jittery square wave pulse to apply to input!
    anyone know how to produce such a signal in cadence tool??

    I'd be appreciated for any hint

    regards
    farid
     
  2. PaulEE

    Member

    Dec 23, 2011
    423
    32
    Define jittery
     
  3. Brownout

    Well-Known Member

    Jan 10, 2012
    2,375
    998
    Which Cadence tool? What type of design entry?
     
  4. farid82

    Thread Starter New Member

    Jan 15, 2012
    8
    0
    Dear PaulEE

    By jitter I mean random variation in rising edge of the pulse, I attached a photo of signal which I need

    regards
    Farid
     
  5. farid82

    Thread Starter New Member

    Jan 15, 2012
    8
    0
    Dear Brownout,
    you're right maybe I was not clear enough,

    I working with cadence spectre ,and I have access to "ahdlLib" and "analoglib" libraries,

    at the input of my design , I just need a square wave pulse with variation in rising edge of the signal .and I don't know how to produce it

    I attached a photo a signal which I need to produce.
    as u can see I need a pulse which rising edge of it start earlier or later than expected ,and its random, I mean some time the rising edge is as expected ,butt some time it starts a bit earlier or later.(which is called jiiter)

    regards
    farid
     
  6. farid82

    Thread Starter New Member

    Jan 15, 2012
    8
    0

    I attached a photo a signal which I need to produce.
    as u can see I need a pulse which rising edge of it start earlier or later than expected ,and its random, I mean some time the rising edge is as expected ,butt some time it starts a bit earlier or later.(which is called jiiter)

    regards,
    farid
     
  7. Brownout

    Well-Known Member

    Jan 10, 2012
    2,375
    998
    Hi farid,

    I dont' know anything about AHDL, but I've used verilog to do this before. Here is some code I copied from another discussion, to show how it was done.

    The important part is in the last line. A function "$random" is added to the clock half-period to achieve the jitter. You might look into the AHDL documentation and see if there is a random function. I'll just bet there is. Let me know if you have any questions about the code.

    Source: http://www.edaboard.com/thread100284.html
     
  8. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Use an ideal opamp or comparator.

    Feed one input a sawtooth wave; one that rises to a maximum value and then suddenly drops; this will establish your base frequency.
    Feed the other input a sine or triangle wave that is a different frequency from the sawtooth wave.
     
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