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problem with spectreRF

abouzied

I have the following question:

If I do iip3 simulation for an LNA and after choosing the output, the iip3 is -3dBm for example.

If I choose the net of the input as the output for iip3 calculation, it will be -3dBm(ideally it should be infinity), Why does this happen ?

I use PSS followed by PAC for simulation.

thanks in advance,

Mohamed Abouzied

Parents
  • Andrew Beckett

    Mohamed,

    I have examples where starting from -50dBm is fine - it depends on the circuit, and simulation setup. 

    Tightening tolerances by a factor of 1000 is probably not sensible - that might actually make things worse.

    As I suggested earlier, you should contact customer support - it's very hard to know what you're actually doing without seeing it. In the case of the app note, it doesn't matter that the curve is inaccurate at -50dBm because the IP3 is being measured at  -40dBm. However, the results look pretty poorly controlled in that app note - so that's why I suggested you look at something more recent.

    So please contact customer support.

    Andrew.

Reply
  • Andrew Beckett

    Mohamed,

    I have examples where starting from -50dBm is fine - it depends on the circuit, and simulation setup. 

    Tightening tolerances by a factor of 1000 is probably not sensible - that might actually make things worse.

    As I suggested earlier, you should contact customer support - it's very hard to know what you're actually doing without seeing it. In the case of the app note, it doesn't matter that the curve is inaccurate at -50dBm because the IP3 is being measured at  -40dBm. However, the results look pretty poorly controlled in that app note - so that's why I suggested you look at something more recent.

    So please contact customer support.

    Andrew.

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