Montecarlo analysis - RF Cafe Forums

 Post subject: Montecarlo analysis

Posted: Sun Nov 02, 2008 10:19 pm 

My question is on Montecarlo and Worst case analysis. I know one can use a commercial CAD simulator to run montecarlo simulations on a design if one knows the tolerances of parts used. But vendors of active devices typically don't provide statistical models for their devices. What sort of tolerance levels (of model parameters) does one assume for the active device?

I have looked up the literature for publications on this topic and I have'nt found much. Any help on this issue would be much appreciated.

 Post subject:

Posted: Thu Nov 06, 2008 5:51 pm 

Hello Seth,

You raise here an interesting question. It is true that manufacturers of active devices don't provide the tolearnces. These tolerances would be the deviations of the device intrinsic parameters like intrinsic capacitances, inductances, equivalent noise sources etc, which are very hard to model and which are process-dependant.

Basically the S-parmaeters of an active RF device are being extracted from the non-linear model provided by the manufacturer. A deviation from the S-paramaters e.g. lot to lot or temperature dependant will be dervided by a deviation in the device internal parmeters. For a given device, a given X% deviation in S21 (gain), is caused by a given Y% deviation in several intrinsic paramaters of the non-linear model. You can ask the device's manufacturer what is for example the expected deviation in S21 from lot to lot, and according to that to change the parameters of the model, which mostly affect the device's gain, by this to get an idea about the estimateded tolerances of the device's parametrs.

Hope this helps!

 Post subject: Re: Montecarlo analysis

Posted: Sun Mar 22, 2009 6:17 am 

Thanks IR for your help.

 Post subject: Re: Montecarlo analysis

Posted: Sun Mar 22, 2009 6:50 am 

By the way, I have seen in the last days that in some Mixed-Signal simulators which are capable to analyze Spice models, there is a possibility of Monte-Carlo analysis with paramater sweep. I was not aware to the recent developments in this area, but more and more manufacturers are providing now Macromodels Spice models for their IC's (like DC-DC converters, broadband amplifier) and also transistor. If I compare it to 2-3 years ago, these models and simulation capabilities were not available then.

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Best regards,

- IR