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idtmod in wreal VAMS (Read 214 times)
deba
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idtmod in wreal VAMS
Sep 28th, 2018, 2:01am
 
Hi,

I am trying to model the VCO in VAMS wreal. There are no electrical signals only digital and wreal signals.

Is it possible to use idtmod(modulo 2*pi integrator) the same way as used in verilog-A.

Thanks
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Ken Kundert
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Re: idtmod in wreal VAMS
Reply #1 - Sep 30th, 2018, 11:55pm
 
One would not use idtmod to write an event driven VCO. The idtmod operator is implemented in the continuous kernel, which would slow the simulation. It is pretty easy to write a event driven VCO model without it. Just do something like the following:
Code:
module vco (out, in);
parameter real kvco = 1e9;
output out;
input in;
wreal in;
reg out = 0;
real freq, half_period = 100e-12;

always #half_period begin
    freq = kvco * in;
    half_period = 0.5/freq;
    out = ~out;
end
endmodule
 

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deba
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Re: idtmod in wreal VAMS
Reply #2 - Oct 1st, 2018, 12:46am
 
Hi Ken,

Thanks for your reply. I am using a similar approach.  A follow up question.

The same event driven can be used instead of idtmod for modelling VCO. Does modelling the VCO in VAMS electrical idtmod more accurate than the event driven VCO model? Event driven the resolution is limited to 1 fs. Using idtmod what level of resolution can be achieved?

I have to model a very low jitter PLL.(<200 fs).

Thanks
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