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Simulators >> Circuit Simulators >> A Problem in LNA simulation
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Message started by lxie on Nov 25^th, 2005, 2:17am

Title: A Problem in LNA simulation
Post by lxie on Nov 25^th, 2005, 2:17am

　　Hi ,
I wanted to use spectre analysis a LNA's voltage gain , but the file spectre.out display 4 subintervals and each one simulated from 0 second to 1.04167ns (because my LNA's fundamental is 960MHz ) ,is anything wrong with this result? Could anybody help me?

Thanks
lxie

Title: Re: A Problem in LNA simulation
Post by sheldon on Nov 25^th, 2005, 2:52am

Ixie,

Could you provide a little more information? For example
your transient statement?

Best Regards,

Sheldon

Title: Re: A Problem in LNA simulation
Post by lxie on Nov 25^th, 2005, 5:18am

In the file of spectre.out we can see this :the first line "Periodic Steady-State Analysis 'pss': fund =960MHz" the second line : "'pss' : time = (0 s -> 1.04167 ns) ,then is the simulation time .And this process repeat 4 times. is it means the circuit not
convergent?

Thank you.
lxie

Title: Re: A Problem in LNA simulation
Post by sheldon on Nov 25^th, 2005, 3:34pm

Ixie,

You are performing a Periodic Steady-State analysis, PSS.
This analysis finds the steady state response of a circuit
over the user defined periood. In your case, the period
is 1/960MHz, or 1.04167ns. A PSS analysis is looking for
the steady-state response. SpectreRF iterates using the
Shooting Newton algorithm to find the circuit's steady-state
response to the periodic input. Please look in the SpectreRF
Theory of Operation for more details.

There is only one solution. The algorithm first makes an
estimate of the steady-state using transient analysis and
then iterates to refine the estimate. In your case three
iterations were required. If you look at the end of the
run there is a report on how close the algorithm is to
converging.

If the algorithm is not converging it will require many
iterations. So it sounds like PSS is working correctly and
PSS is converging. Can you plot the PSS results?

Best Regards,

Sheloon

Title: Re: A Problem in LNA simulation
Post by lxie on Nov 26^th, 2005, 3:31am

You are right , I had checked it .

thanks very much .

Best Regards,

lxie