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Definition of Cut-off Frequency & How to use it correctly

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According to the FAQ " Calculating Impedance in SPECCTRAQuest " the following is stated for when cutoff frequency in simulation preference is set to non-zero values: " The field solver usually provides the frequency dependent RLGC parameters up to 50GHz to cover the asymptotic behavior of those parameters. "

I would like to know how is this 50GHz boundary is being defined and how is this related to the non-zero value that you key into the cutoff frequency menu.

Is this cutoff frequency has anything to do with the rise/fall time of a signal and is this value has any relationship with the one that Howard Johnson has defined in his MAGIC book ( the knee frequency )?

For example, if I have a signal that has an edge rate of 100ps ( 10/90% ) so what will be the cutoff frequency that I should key-in in order to make sure the loss calculated in the field solver will cover the bandwidth of this signal?

Thanks very much.

Michael Chan


Originally posted in cdnusers.org by kingseiko
Parents

  • "Yet, this is not good news for those who are doing postlayout simulation with all the traces involved, would not this be time consuming? It must be...."
    Clearly, I am talking about the case when the simulator goes to 50Ghz and ignoring the set frequency.
    From my experience, and if it is the case( I have Not witnessed what Donald is describing)
    Cadence Folks are quick into issuing a PCR and correcting the issue.



    Originally posted in cdnusers.org by elie
Reply

  • "Yet, this is not good news for those who are doing postlayout simulation with all the traces involved, would not this be time consuming? It must be...."
    Clearly, I am talking about the case when the simulator goes to 50Ghz and ignoring the set frequency.
    From my experience, and if it is the case( I have Not witnessed what Donald is describing)
    Cadence Folks are quick into issuing a PCR and correcting the issue.



    Originally posted in cdnusers.org by elie
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