Finding P-1db and P-3dB in ADS

Hello,
I want to find p1dB and P3dB in ADS for my LNA. Should I plot Pout and Pin in a figure and plot a straight line to find deviation? If I should do that, to see Pout and Pin I should use harmonic balance and a source in the input of the circuit? Cannot I use s-parameters simulation? Please help.

Yes, use Pout vs Pin with a variable power source at the input.
Use harmonic balance, and not linear S-parameter simulation, from the moment that those already measured the scattering parameters at specific input levels.

thank you vfone.
As you see my circuit in the figure, it is based on S-parameters and I do not have model of the transistor. So, I think I cannot use harmonic balance?!
Is there no other way to find P1db or P3db? For example by Power Gain which is available with S-Parameters simulation by this equation:
G=pwr_gain(S, Zs, Zl, Zref)

Sorry f_t, but it's not possible from a set of LINEAR parameters, you need some kind of a nonlinear model to simulate P1dB and so on.

I highly appreciate, johnjoe,

My professor has said that I have to find the amount of two LC filters to adjust P3dB at 0.7 GHz and 0.5GHz with center frequency 0.6Ghz for the circuit attached before. Now, because I cannot obtain P3dB (all parameters are linear), I can not obtain amounts of two filters. Is it true?

If you don't have the nonlinear model of the active device you cannot find any compression points, and also cannot find the values of the passive LC components in this matter.

You explain your problem with wrong definitions...
P3dB or P1dB definitions are different than you're looking for.These are nonlinear compression points and there is no relation between your problem and them..

You're looking for 3dB (1dB) bandpass filter "cut-off" frequencies.In order to do that, you should simply do a s-parameter simulation and then do what you want
Don't involve with nonlinear simulations..

Bigboss,
Thanks.
But, how should I find 3dB (1dB) bandpass filter "cut-off" frequencies by using S-parameters?

So as I understood, you want to design a lc-bandpass filter with center freq. 0.6 ghz and bandwidth(-3db) 0.2 ghz? Just have a look in a book about filter calculation, it's not so complicate. Or use ADS, it has a filter design tool, consider the manual and a simple standard filter is designed in 5 min. If you continue to design, you should also take some impedance matching into account.

It worked. It was a misconception about two similar names. P3dB for filter and P3dB for nonlinear amplifiers.

Thanks

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