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Modeling >> Behavioral Models >> Transient flicker noise model in Verilog-A
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Message started by zjuyifeng on Jul 31^st, 2007, 2:06am

Title: Transient flicker noise model in Verilog-A
Post by zjuyifeng on Jul 31^st, 2007, 2:06am

Does anyone have experience in modeling flicker noise in Verilog-A for use in transient simulations?
I hace to model it .
My simulator is Spectre.
Any ideas would be greatly appreciated.

Thanks !

Title: Re: Transient flicker noise model in Verilog-A
Post by Geoffrey_Coram on Jul 31^st, 2007, 9:46am

Verilog-A has a flicker_noise function.

Spectre knows how to do flicker noise for built-in devices for transient noise.

Hence, I would expect that Spectre could also "do the right thing" for flicker_noise() in a Verilog-A model for transient noise. Otherwise, it's a real nuisance to try to generate time-domain samples of a flicker noise process. I think there are a couple papers on IEEEXplore.

Title: Re: Transient flicker noise model in Verilog-A
Post by zjuyifeng on Jul 31^st, 2007, 5:40pm

But I still don't understand what you mean.

flicker_noise() can only be valid in AC simulation. It is not work in transient simulaiton

Please help me more!!!

Thanks

Title: Re: Transient flicker noise model in Verilog-A
Post by Ken Kundert on Jul 31^st, 2007, 6:37pm

Conceptually you would create a Verilog-A current source model that produced a gaussian white sequence at a fixed rate, and feed that into a fracpole with a slope of -0.5. The resulting voltage would have 1/f distribution.

-Ken

Title: Re: Transient flicker noise model in Verilog-A
Post by Geoffrey_Coram on Aug 1^st, 2007, 5:09am

zjuyifeng wrote on Jul 31^st, 2007, 5:40pm:

flicker_noise() can only be valid in AC simulation. It is not work in transient simulaiton

That's not actually true -- it doesn't work in a standard Spice transient analysis, but standard Spice doesn't know anything about transient noise. The Verilog-AMS LRM should probably have something to say about this. But my point is: flicker_noise() *does* work in transient noise analysis; try an example and see what you get!

Code:

// mynoi.va
module mynoi(a,b);
inout a,b;
electrical a,b;
analog
I(a,b) <+ V(a,b) + flicker_noise(1000, 1, "flicker");
endmodule

Put this in a netlist with a current source driving it, run a transient noise analysis.

Title: Re: Transient flicker noise model in Verilog-A
Post by zjuyifeng on Aug 1^st, 2007, 8:23pm

Thanks for your help.

I had access to the fracpole model.

But when simulated, a error came out.

" PF0 is an instance of an undefined model fracpole "

Can you help me ?

Thanks

Title: Re: Transient flicker noise model in Verilog-A
Post by Geoffrey_Coram on Aug 2^nd, 2007, 5:55am

Are you using a current version of Spectre?

Title: Re: Transient flicker noise model in Verilog-A
Post by zjuyifeng on Aug 2^nd, 2007, 6:24am

a current version of Spectre?

The spectre using is the voltage version ? How to set the spectre for the current version?

Thanks

Title: Re: Transient flicker noise model in Verilog-A
Post by Ken Kundert on Aug 2^nd, 2007, 10:59am

The question is "Are you using a recent version of Spectre?". Both the fracpole and Geoffrey's suggestion require a relatively recent version of Spectre.

To test to see if Spectre supports fracpoles, type "spectre -h fracpole" into a unix command line.

-Ken

Title: Re: Transient flicker noise model in Verilog-A
Post by zjuyifeng on Aug 2^nd, 2007, 10:46pm

warning from spectre
fracpole : no such component

It's a bad nows for me!!

Title: Re: Transient flicker noise model in Verilog-A
Post by Geoffrey_Coram on Aug 6^th, 2007, 6:24am

Did you try flicker_noise() in a time domain noise simulation? Of course, time domain noise is also a somewhat recent addition to Spectre, and maybe they didn't get the Verilog-A flicker noise implemented in the first go-round, but it does work for me in my version of Spectre (which also has fracpole ...).