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

时间:04-05 整理:3721RD 点击:
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?

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..

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.

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.

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

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