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Design Languages >> Verilog-AMS >> How to get a Gaussian source using Verilog-AMS
https://designers-guide.org/forum/YaBB.pl?num=1332404760

Message started by ahutianyi on Mar 22^nd, 2012, 1:25am

Title: How to get a Gaussian source using Verilog-AMS
Post by ahutianyi on Mar 22^nd, 2012, 1:25am

Hi,guys
I'm modeling a ADC.However,I meet a problem when to model a random source.I need a 255 outputs Gaussian source,and I find it difficult to realize that using "$rdist_normal(seed,mean,deviation)". :'(
Is there anybody who can help me?
Thanks very much!

Title: Re: How to get a Gaussian source using Verilog-AMS
Post by ahutianyi on Mar 23^rd, 2012, 12:56am

ahutianyi wrote on Mar 22^nd, 2012, 1:25am:

Hi,guys
I'm modeling a block.However,I meet a problem when to model a random source.I need a 255 outputs Gaussian source,and I find it difficult to realize that using "$rdist_normal(seed,mean,deviation)". :'(
Is there anybody who can help me?
Thanks very much!

Title: Re: How to get a Gaussian source using Verilog-AMS
Post by ywguo on Mar 23^rd, 2012, 7:09am

Hi,

What do you mean when saying 255 outputs Gaussian source? What do you get using your code?

Is it correct for the code
V(offset[i]) <+ V(result[i]);
result is defined as real. I don't know what the compiler/simulator do with the above statement.

Yawei

Title: Re: How to get a Gaussian source using Verilog-AMS
Post by Geoffrey_Coram on Mar 26^th, 2012, 10:46am

I'm sure he meant

V(offset[i]) <+ result[i];

Title: Re: How to get a Gaussian source using Verilog-AMS
Post by Geoffrey_Coram on Mar 26^th, 2012, 10:52am

But I think you need two integers, one for the loop index and a second for the seed; as it is,
V(offset[1]) = $rdist_normal(1, mean, dev)

That is, the call to $rdist_normal that sets output[1] is always made with the seed=1, so it will get the same value for each and every timepoint.

Title: Re: How to get a Gaussian source using Verilog-AMS
Post by ahutianyi on Mar 27^th, 2012, 5:01am

I meant that I want to get a series of random sources.All the sources follow the Gaussian distribution.I found the sytax error---V(offset[i])<+V(result[i]).However,I can't realize the resources yet.Is there anybody can help me?

Title: Re: How to get a Gaussian source using Verilog-AMS
Post by Geoffrey_Coram on Mar 27^th, 2012, 11:07am

We can't help you if we don't understand what you are trying to do.

Are you sure you want a new $rdist value for *every* timepoint?

Perhaps you want to use a clock input, or a timer event, to signal when to generate new random values.

integer i, myseed;
genvar j;
@(initial_step)
myseed = 0;

@(timer(0,1u)) begin
for (i=1; i <=256; i++) begin
result[i] = $rdist_normal(myseed, mean, dev);
end
end

for (j=1; j <=256; j++) begin
V(offset[j]) <+ transition(result[j], 0, 1n, 1n);
end

Title: Re: How to get a Gaussian source using Verilog-AMS
Post by ahutianyi on Mar 27^th, 2012, 11:47pm

Thanks a lot.I'm sure I want to realize a series of Gaussian voltages,and the voltages are stable.I use these voltages as the sources of the latter blocks. :)

Title: Re: How to get a Gaussian source using Verilog-AMS
Post by Geoffrey_Coram on Mar 28^th, 2012, 4:53am

Oh, if the voltages are stable (ie, don't change in time, but are picked randomly at time zero), then

integer i, myseed;
genvar j;
@(initial_step) begin
myseed = 0;
for (i=1; i <=256; i++) begin
result[i] = $rdist_normal(myseed, mean, dev);
end
end

for (j=1; j <=256; j++) begin
V(offset[j]) <+ result[j];
end