Help on IP3 simulation in cadence

[David2004]

iip3 simulation in cadence

Normally I can get IP3 from PSS or PSS/PAC simulation in IC4.46, QPSS or QPSS/QPAC simulation in IC5.0. When I designed LNA before I can easily get a clear 3:1 slope. But when I use cadence to run the IP3 simulation over one single device, I can not get the same 3:1 slope no matter how I changed the tolerance parameters. I did not use matching network in my simulation as in LNA design, only for the device itself. Anybody met the similar problem before on IP3 simulation? Any suggestions? Thanks!

 

[dsjomo]

iip3 cadence

Did you set the small-signal power level (or amplitude level) of PAC?? It's located in PORT instance's characteristic menu.

You said you did not get a 3:1 relation, so what kind of the curve did you see??

 

[David2004]

lna iip3 simulation

Yes, I already set PAC magnitude(dBm).

Not a smooth curve, the slope is less than 3:1.

 

[dsjomo]

ip3 simulation + cadence + qpss

Maybe you can try a lower power level. For example, set input power level to -40 dbm if the estimated IIP3 = -10 dbm.

 

[David2004]

ip3 simulation slope

I already tried that, still did not work.