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Questions about VCO simulation using SpectreRF...

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zhangjavier

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cadence vco simulation

I use PSS to simulate VCO. A voltage pulse with amplitude of 0.1V is added to stimuli the circuit and the circuit can oscillate. I just wonder whether this simulation really represent the circuit's performance since 0.1V is large compared to the noise.

And another question is that how to reduce the simulation time? With this method, it takes me a few minutes to finish the simulation.

Any good tutorials about VCO simulation in SpectreRF?

Thanks~~Bow...
 

if you add a stimulus

your loading the osc circuit

so remove it and instead make it self osc using a res and a cap
as it should be

youll always load any oscilator using any type of probe
be in inputs or outputs

you may find your stimulating the wrong point in the circuit
if it take so long to boot the mixed sim engine
 

in PSS simulation
you can set "Beat frequency" near your OSC freq
it will be able to quick finish simulating
 

Thank you guys.

Now I am thinking manye that my oscillator doesn't start up to oscillate at all. It is just a simpel PMOS cross-couple structure on .18um CMOS. The tail current is about 10mA. Isn't this current enough to oscillate?
 

try to check the resistance of ur resonator , and design the negative gm of the cross coupled pair , to be 2 to three times of the resistence of he resonator

, and try to make the VDD as a step


khouly
 

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