It's pretty simple--the probability density of the sum of two uncorrelated variables (e.g. sines of incommensurate frequency) is the convolution of the two individual densities. So the nasty peaks at the ends get smoothed off.
He's just grouchy because he doesn't get any meat in his soup. ;)
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510
hobbs at electrooptical dot net
http://electrooptical.net
I added the s/h to fake the DAC clock and tried a triangle, under the assumption that my FPGA guy could make a triangle more easily than a pair of sines (which would probably just be a huge lookup table.) It was awful.
Two sines with the s/h aren't bad.
How do you get LT Spice to make bandlimited Gaussian noise? I could try that, too.
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510
hobbs at electrooptical dot net
http://electrooptical.net
Of course that doesn't work in transient simulations. I'd probably do a Box-Mueller noise generator followed by a BPF, but that would take some figuring out.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510
hobbs at electrooptical dot net
http://electrooptical.net
I'd love to see that. I haven't got around to learning how to drive Matlab or its clones. Maybe try more than two uncorrelated sines?
I tried adding a histogram block (swept window comparator and lowpass filter) but it ran really slow, and I put that aside for now. That would be a cool intrinsic for LT Spice. Or I guess I could export a waveform and sic a PowerBasic program on it. The other thing I'd like to have is a time-domain Gaussian noise generator. Anybody want to write one? $100? Lunch at Zuni?
it was an attempt at a Box?Muller transform, two of them to get it symmet ric and some hacks on time to get some random numbers, I'm not sure how well it works I'm not sure I understand the Time variable in ltspice
Two values at a time--it uses polar coordinates. Google "Box-Mueller". (Numerical Recipes has a good discussion.)
You can do a lot of that stuff by creative use of Boolean operators. (Old versions of Mathcad had a lot of the same limitations, so I'm pretty used to it.) I recently upgraded to the 2001i edition.
[Mathsoft claims that it doesn't run on Win 7, but it actually runs fine if you copy the installation from XP and run the registry tool they supply (regtool.exe). Same with Wine. It just doesn't install there.]
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510
hobbs at electrooptical dot net
http://electrooptical.net
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