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    How can I obtain selectivity plot of frequency divider?

    When seeing papers regarding frequency dividers, I noticed that authors usually use sensitivity plot as in the attachment to show the frequency selectivity as in the bellow figure.

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    And I wanna use this plot to design frequency divider of which selectivity for my target frequency is good.

    Please let me know the way they plot it and how to simulate it in simulation step.

    Thank you

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    Re: How can I obtain selectivity plot of frequency divider?

    General speaking, the Frequency Dividers have Signal Level Threshold so that the Divider will either oscillate @ its own natural frequency or its' outputs become zero under this threshold level.
    Regarding to those definitions, the divider sensitivity is a metric of this phenomena.I mean, the divider will not divide the signal anymore OR it will oscillate..
    This the sensitivity figure of merit..
    It's possible to see in even simulations.



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  3. #3
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    Re: How can I obtain selectivity plot of frequency divider?

    Thank you for your reply BigBoss.

    As you know, in the vicinity of natural frequency in the sensitivity plot I attached frequency divider will operate with low input power (amplitude).
    So, I wanna get that plot in simulation to check the sensitivity and lower power dissipation.

    Actually, I just want to know how to plot that plot in simulation and it is why I posted my post.
    Please let me know the way to plot sensitivity plot if you know.



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  4. #4
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    Re: How can I obtain selectivity plot of frequency divider?

    You can simulate such divider by varying the input amplitude @ each frequency so you can observe the output amplitude in HB analysis.
    When the output amplitude drops down to certain level ( under for instance 0.5V or less ) you note this point the repeat this simulation in the band of interest by certain steps.
    It's very difficult to see the oscillation due to low input amplitude but a well set-up transient simulation may help you.



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