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freq_meter component in ahdlLib

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Dear all,
 
I'm using freq_meter component from ahdlLib to calculate instantaneous frequency of an oscillator. While doing Spectre simulation, I'm getting the error as
 
==========================================================
Error found by spectre at time = 20.6089 ns during transient analysis `tran'.
    Signal FF(FREQ_OUT) = 2.18688 GHz exceeds the blowup limit for the quantity
       `FF' which is (1 GHz). It is likely that the circuit is unstable. If
       you really want signals this large, set the `blowup' parameter of this
       quantity to a larger value.
==========================================================
 
Please let me know how to resolve this issue.


Originally posted in cdnusers.org by vj
Parents

  • Take a copy of the freq_meter model, and change the section at the top which creates a nature Frequency to the following:

    nature Frequency
    abstol = 1;
    access = FF;
    blowup = 1e12;
    units = "Hz";
    endnature

    The default blowup is 1G, which is a little small if you're measuring frequencies around 1GHz. Note I also increased abstol, since the accuracy requirements shouldn't be so tight if you have GHz signals. Even 1 might be a bit small (normal practice is to set abstol to a millionth of a typical signal level).

    Regards,

    Andrew.


    Originally posted in cdnusers.org by adbeckett
Reply

  • Take a copy of the freq_meter model, and change the section at the top which creates a nature Frequency to the following:

    nature Frequency
    abstol = 1;
    access = FF;
    blowup = 1e12;
    units = "Hz";
    endnature

    The default blowup is 1G, which is a little small if you're measuring frequencies around 1GHz. Note I also increased abstol, since the accuracy requirements shouldn't be so tight if you have GHz signals. Even 1 might be a bit small (normal practice is to set abstol to a millionth of a typical signal level).

    Regards,

    Andrew.


    Originally posted in cdnusers.org by adbeckett
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