calculating of IIP3 for Receiver chain

  1. nmw
    I am using Receiver chain consists of LNA,N-path filter,Gm,Mixer and TIA stage.
    I need to calculate the cascaded IIP3 with above stages.I have filter in TIA stage to reject the interference tones.

    Now I am giving two interferes with 2.8MHz and 5.6MHz offset from the carrier.These signals passed through LNA and amplifies ,generated IM3 components at 2f1-f2 and 2f2-f1.
    These four signals mixed with Lo and down converted to IF.IM3 component fall on DC and 2.8MHz and 5.6MHz signal passed to Filter.Filter will attenuate the two interferes as per requirement.

    I observed in simulation tools are taking interfere level at output and IM3 components amplitude taking IM3 level.using these two values tools are calculating IIP3 = 1/2(3Iinterferer-Pimd).

    But Interferes level after attenuating filter,it is very IIP3 value also coming as low.
    Is any formula to calculate exact cascaded IIP3 with filter role off?if yes,please help on this topic.
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