Error in VCO post layout Simulation..

[s.b.biradar]

hi,
I am getting the results In VCO prelayout simulation,but in post layout simulatiuon following errors are coming....

ERROR (SPCRTRF-15050): V(net5,net7) is too small to reliably detect the period of the oscillator.Perhaps nodes with insignificant signal levels were chosen, or perhaps the oscillator was never properly started.

Analysis `sweeppss-000_pss' was terminated prematurely due to an error.

Error found by spectre during Sweep analysis `sweeppss'.
ERROR (SPCRTRF-15024): The pnoise analysis was skipped because a PSS analysis must be run first.


Can anyone tell me how to resolve it...
Thank You..

 

[oermens]

did you put initial condition on your oscillator node? try to tighten your tolerances.

 

[saro_k_82]

You will also have to provide sufficient tstab before pss.

 

[s.b.biradar]

did you put initial condition on your oscillator node? try to tighten your tolerances.

hi,
i have given the conditions:
In PSS:
Beat frequency: 2GHz
Number of harmonics :2
errorpreset:Conservative
tstab:450ns
In Pnoise:
sweep type:Relative,
Relative harmonic:1,
sidebands:7,
noise type:sources.

Do i need to set any other options.Plz guide me..

 

[saro_k_82]

The settings look fine to me. Did you run a tran simulation to see the circuit oscillate? If it oscillates properly in a tran simulation, it is not normal to see this warning in pss. Set some initial conditions to help the oscillator startup quickly.

 

[s.b.biradar]

The settings look fine to me. Did you run a tran simulation to see the circuit oscillate? If it oscillates properly in a tran simulation, it is not normal to see this warning in pss. Set some initial conditions to help the oscillator startup quickly.

thank you..
I am getting the oscillation in prelayout simulation and post-layout simulation with "C" extraction only. But if i simulate post-layout with both "R"&"C" extraction then its unable to oscillate.
Can you please guide me how to solve this problem...

 

[oermens]

what type of oscillator are you simulating/extracting? is your bias current correct in postlayout? did you try wider traces?