High NF LNA with non ideal inductor for I/P matching

[analog_chip]

I am designing a square law LNA. But when I replace ideal inductors of matching network with non-ideal (Q=14) ones then NF increases by 6dB!!! Can anyone suggest whats happening?

 

[BigBoss]

So does have the "real" inductor value as same as with the ideal one ??
Have you verified it with EM simulation ???If it has, check the sensitivity of your LNA against Q factor of Source Inductor.
But I personally believe that the L value of the real inductor is not same as ideal one..

 

[vfone]

Experimentally was found that high-pass topology for LNA input matching network is less sensitive to the influence of the inductor-Q on the Noise Figure.
If you have the right matching values to get gamma-optimum, there should not be more than 0.5dB degradation of the noise figure when the Q of the inductor varies from ideal to 14.
This happen mainly due to decreasing the gain of the LNA.

 

[analog_chip]

Thanks BigBoss & vfone for replying. Actually its a square law lna+mixer. It uses MOS nonlinearity for downconversion. I guess noise squared is getting folded and spoiling it.

 

[analog_chip]

Hi BigBoss,
Both are ideal inductors but in the second case I added Rs to model Q.