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Noise simulation in Complex filter

Cadence recommends following way to do the noise simulation in Complex filters: -

According to principle of superposition noise can be calculated as follows:
1. Calculate output noise (V**2/Hz) when only portI is active:
- at Iout: Ioutn_I(f);
- at Qout: Qoutn_I(f).
2. Now calculate output noise (V**2/Hz) when only portQ is active:
- at Iout: Ioutn_Q(f);
- at Qout: Qoutn_Qf).

Now you can calculate the total otput noise (V**2/Hz) at both outputs:
Ioutn(f) = Ioutn_I(f) + Ioutn_Q(f);
Qoutn(f) = Qoutn_I(f) + Qoutn_Q(f);
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The complex BPF is made of 2 LPFs. Both of them have gain = 0dB. Also Gain is 0dB for complex out to complex input.
Now I see that input referred noise is double that of output referred noise even though gain is 0dB . I don't know why this is happening. Please help.
Thanks
Megh

Tawna over 15 years ago

Hi Megh,
You don't say what type of noise analysis you are running.... Is this ac noise, spectreRF pnoise, etc. ?

For a summary of existing noise documentation, you may want to take a look at:

Summary of existing documentation on various RF related noise analyses
http://support.cadence.com/wps/mypoc/cos?uri=deeplinkmin:ViewSolution;solutionNumber=11585972

(I suspect that you may be referring to COS Solution 11162588 . You may want to consider filing a Service Request so that a Support AE can assist you in greater detail.)
best regards,
Tawna
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Megh over 15 years ago

Hello Tawna,
Thanks for replying. I am performing AC Noise analysis.
Please let me know what do you think on the stated problem.
I will file an SR on this.
Thanks
Meghraj
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