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 spectrum function in OCEAN 

Last post Tue, Aug 27 2013 9:13 PM by Andrew Beckett. 2 replies.
Started by ksnf3000 13 Aug 2013 06:01 AM. Topic has 2 replies and 385 views
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  • Tue, Aug 13 2013 6:01 AM

    • ksnf3000
    • Not Ranked
    • Joined on Tue, Oct 30 2012
    • Posts 13
    • Points 200
    spectrum function in OCEAN Reply

    Hi All,

    I am trying to calculate the Effective no.of bits,SINAD,SNR etc. for a delta-sigma ADC. As per the OCEAN reference document on page 427  for the function "spectrum" , it shows that these parameters are calculated using the DFT of any given input signal. 

    However,when I am using the below expression its showing that evaluation of the expression has failed. 

    spectrum (dft(VT("/net028") 0 1e-06 4096 "Rectangular" 1 "default") 4096 500K 1 2G "Rectangular" nil "sinad")

    Please provide your insights on this and what could be the possible solution for this.

    FYI: I calculated the DFT separately and used the spectrum function which gave me an erroneous result( I assume!!) 

    Regards,

    Kashif 

    • Post Points: 5
  • Tue, Aug 27 2013 1:52 AM

    • ksnf3000
    • Not Ranked
    • Joined on Tue, Oct 30 2012
    • Posts 13
    • Points 200
    Issue in "spectrum" function of Cadence Reply

     Hi All,

    While calculating the SNR,ENOB using the "spectrum" function in calculator,I seem to be getting rather erroneous results. As seen in the attachment, I am getting "-1.9 bits" as my resolution and the SNR/SFDR is 0!!  I really don't understand this why.

    I have followed the below steps for the above results

    Sent the transient output data to calculator. This is my input signal to the spectrum function.

    32768 is the number of bins I desire to use

    800K is the bin size. My transient simulation time was 1.25u

    1 is the starting FFT frquency

    13.1072G is the end FFT frequency.  // I had also performed a dft of the same signal from which I obtained the input & output signal       frequencies.

    Please let me know what is the problem. Is this an issue with Cadence or in the manner in which the computation is being done?

    Thanks!

    Kashif

     


    • Post Points: 20
  • Tue, Aug 27 2013 9:13 PM

    Re: Issue in "spectrum" function of Cadence Reply

    Kashif,

    It's hard to debug without seeing the input data. Please contact customer support.

    Kind Regards,

    Andrew.

    • Post Points: 5
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Started by ksnf3000 at 13 Aug 2013 06:01 AM. Topic has 2 replies.