AWGN in Cadence?

Hello!

Anyone have a way to add additive white Gaussian noise to nodes in a
Virtuoso schematic and can be simulated in Affirma/Spectre/Analog Artist?

Thanks,
-Jason

 

Jason,
There are multiple ways of doing this,
If the simulator is spectre

1. Using verilog-A noise functions
2. Adding a white noise current source
3. Adding a white noise voltage source

I beleive i saw the above sometime before @ source link, i am not able
to recollect it now, seach sourcelink for details

If you use spectre-Rf as your simulator, you could do a PNoise nalysis
by adding sources of noise on the nodes(port components?)

 

Partha,

Thanks for your reply. I'm not too familiar with Verilog, but I managed to
modify the Cadence Verilog-A noise_src module to make the random number
generator gaussian. However, this requires me to add a noise source in
series with all the nodes to which I want to add noise. Is there a better
way to do this? For example, is there an operator other than "<+" in
Verilog that will simply provide an additive voltage source to an existing
node?

In addition, does the following Verilog-A module accurately (realistically)
model AWGN if put in series with an existing node?

`include "discipline.h"
`include "constants.h"

module noise_src(vout,ref);
output vout;
input ref;
electrical vout,ref;
parameter real amp = 0.2 from [0:inf);
parameter real att = 10 from [0:inf);
integer seed;

analog begin
@ (initial_step) begin
seed=23;
end

V(vout,ref) <+ amp * $dist_normal(seed,0,1)/att;
$display ("seed is %d",seed);
end

endmodule

Thanks,
-Jason

 

Jason,

I am also not so familiar with verilog-A , but I believe there is a
ready-made function white_noise

The way I would do it is with a resistor and a VCVS, because I find it
more readable to have everything in the schematic rather than in
verilog-A code, when practical.