--- In LTspice@..., "gm4dij <brian.howie@b...>"
<brian.howie@b...> wrote:
--- In LTspice@..., Panama Mike <panamatex@y...> wrote:
You might be able to use the rand() function
to get what you're looking for. Check the
example ./LTC/SwCADIII/examples/Educational/PLL.asc
There it is used to generate a random bit stream
by boolean comparison to 0.5.
--Mike
--- "ingodettmann
<ingod@y...>"
<ingod@y...> wrote:
Hi everbody,
does anyone know, how I can add a noise source in a
transient
simulation (if it is possible at all)?
I tried to modell a noise source with a behavioral
voltage source
but i didn't work.
rand and white on their own are no use -these are rectangular
random
variables.
Use a behavioural voltage source with V for example
V=SQRT(-2*LN(white(time*1.07G)+0.5))*COS(2*PI*(white
((time*0.93G+0.5)))
This is the Box-Mueller algorithm for Gaussian Noise. You need two
independent random variables. The factors 1.07 and 0.93 is an
attempt
to do this. You will need to alter these, and the time step to get
what you want. You also may need to scale to get the correct rms
value in your noise bandwidth.
It's not perfect.
Hello Brian,
thanks for the formula. I googled and found this reference.
I couldn't resist to test it immediately in LTSPICE.
I have got some extremely high peaks(30V) at 47us, 48us and 84us
with the setting ".tran 0 100000n 0 0.5n".
So the formula needs a little change to avoid extreme values at
log(0).
The original formula:
V=SQRT(-2*LN(white(time*1.07G)+0.5))*COS(2*PI*(white(time*0.93G+0.5)))
My slightly modified formula for LTSpice:
V=SQRT(-2*LN(0.999997*white(time*1.07e9) +0.50001))*COS(2*PI*white
(time*0.93e9+0.5))
This B-source doesn't have the above mentioned "defects".
Best Regards
Helmut
