In my last thread I asked about using op amps and low-pass filters to produce subsonic noise from a noise generator. Now I'm thinking about a different way to attack this problem.
Maybe it's time to go into the digital domain. My thought is this: use my same simple noise source (reverse-biased transistor junction), but immediately digitize the noise, probably with a simple squaring circuit (infinite-gain op amp stage).
Then, what if I just "stretch" the signal, by simply copying it over a longer time base? The diagram below should explain this:
**broken link removed**
First question is how to do this? Obviously, this would most easily be done by a microprocessor in software. This would allow one to easily change the "stretch factor" and thus the frequency spectrum. I know how to do that. I'm curious about doing this in hardware, though: can you think of a simple, elegant way to do this with a few gates? I can't at the moment, but haven't really thought it out (which I will do).
Of course, this will result in a fairly degraded form of the noise signal, since all amplitude information is lost. (It would at least preserve the randomness of the zero crossing spacings.) It's a quick-and-dirty, brute-force way of getting a usable LF signal. Much better would be to use an A/D converter (or does anyone have any other ideas how this could be done to preserve at least some of the original waveform?).
As always, thanks in advance.
Maybe it's time to go into the digital domain. My thought is this: use my same simple noise source (reverse-biased transistor junction), but immediately digitize the noise, probably with a simple squaring circuit (infinite-gain op amp stage).
Then, what if I just "stretch" the signal, by simply copying it over a longer time base? The diagram below should explain this:
**broken link removed**
First question is how to do this? Obviously, this would most easily be done by a microprocessor in software. This would allow one to easily change the "stretch factor" and thus the frequency spectrum. I know how to do that. I'm curious about doing this in hardware, though: can you think of a simple, elegant way to do this with a few gates? I can't at the moment, but haven't really thought it out (which I will do).
Of course, this will result in a fairly degraded form of the noise signal, since all amplitude information is lost. (It would at least preserve the randomness of the zero crossing spacings.) It's a quick-and-dirty, brute-force way of getting a usable LF signal. Much better would be to use an A/D converter (or does anyone have any other ideas how this could be done to preserve at least some of the original waveform?).
As always, thanks in advance.