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PSS analysis: using variable for beat frequency

frasheed

Hello,

I have a ring oscillator design and I am running PSS and pnoise analysis using ADE L. For calculating the phase noise and jitter I want the PSS beat frequency to be calculated from my oscillator output i.e. I don't want to manually enter any numerical value for beat frequency. I tried to calculate the frequency by running transient simulation and then adding that variable in beat frequency option in pss analysis but it gives me error that it is not valid variable or expression. Can anyone give me hint how to this ? I am using ADE 6.1.6.500.10

Thanks

Parents

  • When simulating an oscillator in PSS, you need to check the box labelled "oscillator" and then tell it where the output of the oscillator is (this should be the nodes where the fundamental can be found - so if you have an oscillator followed by a divider, it should be the output of the divider).

    You have to give an estimate of the oscillation frequency to give the simulator a clue, but it doesn't have to be very accurate. PSS will solve for the actual oscillation frequency and so there is no need to be terribly accurate here - the chances are that you wouldn't have been able to enter it accurately enough anyway.

    So there is no need to try to calculate it yourself, unless you're trying to come up with a better estimate - but calculating it from a transient simulation is pretty pointless. It would only be if you have a very wide range of frequencies and can estimate it from one of the variables (e.g. a control word) for the design that it would be worthwhile.

    Note: Do not use the "oscillator" mode unless it is a free running oscillator. I've seen people use this when they have a driven circuit and they can't be bothered to work out the beat frequency. Well, this will mean that the simulator is trying to solve an unknown which is not unknown, and will lead to an ill-conditioned matrix and probably convergence difficulties...

    Regards,

    Andrew.

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  • When simulating an oscillator in PSS, you need to check the box labelled "oscillator" and then tell it where the output of the oscillator is (this should be the nodes where the fundamental can be found - so if you have an oscillator followed by a divider, it should be the output of the divider).

    You have to give an estimate of the oscillation frequency to give the simulator a clue, but it doesn't have to be very accurate. PSS will solve for the actual oscillation frequency and so there is no need to be terribly accurate here - the chances are that you wouldn't have been able to enter it accurately enough anyway.

    So there is no need to try to calculate it yourself, unless you're trying to come up with a better estimate - but calculating it from a transient simulation is pretty pointless. It would only be if you have a very wide range of frequencies and can estimate it from one of the variables (e.g. a control word) for the design that it would be worthwhile.

    Note: Do not use the "oscillator" mode unless it is a free running oscillator. I've seen people use this when they have a driven circuit and they can't be bothered to work out the beat frequency. Well, this will mean that the simulator is trying to solve an unknown which is not unknown, and will lead to an ill-conditioned matrix and probably convergence difficulties...

    Regards,

    Andrew.

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