Problem with ADS simulation on LNA

Hi guys!
Got a problem here.
My simulation result for S11 is ~-0.1dB, but S22 seems normal with -18dB. The gain is nice too, 20dB.
But in actual, the demoboard shows that S11 should get ~ -8dB.
What's wrong with my simulation? It's just a simple S-Param simulation and the Ids seems okay.
Oh ya, I'm measure in 2.5GHz.

Have you simulated your board in Momentum ?The difference might come from this..

I'm measure in around 2.5GHz.
Do you think microstrip line has major effect on my S11?

Check if the LNA bias current is the same as in the S-parameters file used in the simulation.

Also for better accuracy, the simulation shall contain all the parasitics of the components and S-parameters of each passive component. For example SRF of C and L could dramatically affect a high frequency simulation.

0.1dB vs 8dB is a big different....please check & verify the input side connection...there should be a significant mistakes (i.e...open, short)

Hi vfone,
The bias current is the same as what I get in actual board. If components is a matter, why I can get S22, S21, S12 but not S11?

PS:
Hi rfreak,
If the input side got mistakes, I won't get 20dB gain, right?

I agree, if you have a short or open at the input, the gain (or S21) will be low.
But S11 could be different from the simulation when other S-parameters are relative OK, and the reason could be real-life parasitics, losess, or resonances of components, which may not be taken in consideration by the simulation.
Also sometimes the reason could be a bad S-parameters model released by the manufacturer.

I'm using components from the same manufacturer. If you say got parasitics or losses problem, why it didn't affect S22?
Sorry, I'm still no idea what happening here...

PS:
Guys! I know what's the problem. It's just because of my common source MOSFET problem.
Thanks for help!

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