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Design Languages >> Verilog-AMS >> How to creat a VCO model with jitter in VerilogA
https://designers-guide.org/forum/YaBB.pl?num=1155647976

Message started by semitao on Aug 15^th, 2006, 6:19am

Title: How to creat a VCO model with jitter in VerilogA
Post by semitao on Aug 15^th, 2006, 6:19am

Hello! :)
I just read the Modeling Jitter in PLL-based Frequency Synthesizers by Ken Kundert. In this paper, there is a VCO model that includes accumulating jitter. But this model generates square waves, I want a VCO model generates sine waves. How can I modify this model to generate sine waves?

Best regards!

Title: Re: How to creat a VCO model with jitter in Verilo
Post by Ken Kundert on Aug 15^th, 2006, 8:32am

In the VCO model given in the paper replace the last line of the model,

Code:

V(out) <+ transition(n ? Vhi : Vlo, 0, tt);

with one that computes a sine wave based on the phase variable already present in the model.

Code:

V(out) <+ ampl*cos(phase);

-Ken

Title: Re: How to creat a VCO model with jitter in Verilo
Post by semitao on Aug 15^th, 2006, 5:44pm

Thanks, Ken.
I have tried this statement. When I used a 1V voltage as the input signal, the output of VCO is very strange. I don't know the reason.

Best regards!

Title: Re: How to creat a VCO model with jitter in Verilo
Post by Ken Kundert on Aug 15^th, 2006, 6:19pm

try putting a boundstep() function to assure that the simulator takes a reasonable time step. The boundstep should be no more than 0.1T.

-Ken

Title: Re: How to creat a VCO model with jitter in Verilo
Post by semitao on Aug 15^th, 2006, 7:01pm

Thanks, Ken.
I have tried your method, and VCO works. Thank you!

Best regards!

Title: Re: How to creat a VCO model with jitter in Verilo
Post by semitao on Aug 15^th, 2006, 7:07pm

By the way, why the model doesn't need the bound_step statement, when the VCO outputs the square waves.

Best regards!

Title: Re: How to creat a VCO model with jitter in Verilo
Post by Ken Kundert on Aug 16^th, 2006, 12:02am

The transition statement forces time points at the corners of the waveform.

Title: Re: How to creat a VCO model with jitter in Verilo
Post by semitao on Aug 16^th, 2006, 12:34am

Thank you! ;)