Check my IIP2 simulation method using QPSS + QPAC

[tangqin55]

Good afternoon everybody!
Last night I simulated IIP2 use QPSS+QPAC, In the Direct Plot Plot I choose 2rd, and selected 2nd order Harmonic 1.3999G -1 -1 and 1st order Harmonic 1.4001G 1 -1.The sim parameters :fRF=1.401G fLO=1.4G, the second tone is 1.4011G. so fIF=1MHz.But the waveform was strange. Is this sim method right? Why is IIP2 so small? How to sim IIP2?

 

[noiseless]

Is it IIP2?

it is wrong one. for the nonlinearity simu of downmixer, harmonics are all in the low frequency part

 

[DZC]

Re: Is it IIP2?

I know IM2 signal is located near the LO frequence(fLO±(fRF1-fRF2)) and so it is easily filtered by LPF. In a ZIF receiver, the IM2 influences the output by adding to the output without mixing with RF signal. so I am confused by the importance of IIP2, I think isolation is very critical.

If it's wrong, how to simu IIP2?

 

[noiseless]

Is it IIP2?

you are wrong
it should be fRF1-fRF2, and it will not be filtered out by LPF. it will affect ZIF performance greatly.

 

[hilpp]

Is it IIP2?

yes, you are right the fRF1-fRF2 will present at the IF port without frequency translate.