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Simulators >> RF Simulators >> strange problem ahout IIP3
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Message started by augjan on Jul 1^st, 2007, 6:50pm

Title: strange problem ahout IIP3
Post by augjan on Jul 1^st, 2007, 6:50pm

When I simulated IIP3 of a Double-balanced CMOS Mixer, I find the slope is not 3 but about 2.35, so selecting different input amplitude to extrapolate, the IIP3 result is different. Why dose this instance occur? When meeting this problem, how can I simulate IIP3?
I set amp_RF=-60dBm and amp_LO=0dBm,but the result was still strange which can be seen in the picture. I think the input amplitudes is small enough, isn't it?

Title: Re: strange problem ahout IIP3
Post by didac on Jul 1^st, 2007, 11:05pm

Hi,
I think the range of extrapolation points that give a best result in this case is something between -50 and -30 dBm, in this range I expect a little drift in the final value(<1dB).

Title: Re: strange problem ahout IIP3
Post by gavi on Aug 14^th, 2007, 8:24am

Hi,

The simulation result is affected very much, for small signal levels, by tolerance options.
You can rerun the simulation by choosing reltol 0,0001, vastol 1e-6 and iabstol 1e-12.
You have to choose ep to a value only when the slope is close to 3.

Best regards,
Gavi