How do I demodulate a signal?

[Williamx]

I need to output a low frequency signal (between 2Hz and 30Hz) between the output of one sound card to the input of another sound card between two PC's. The soundcards are not designed for frequencies below 30Hz. Therefore I need to use Frequency Modulation (or AM, or PCM) at the output side to create a signal of, for example, between 102Hz and 130Hz. How can I accurately Demodulate the received signal so I can process it as the originating 2Hz to 30Hz signal into my processing worksheet? I figure since DASYLab supports AM, FM and PCM that it would also support the reverse process. How would I do that?

[lab_boy]

Hey

It depends on what signal you want to demodulate. AM demod will be the simplest one. You multiply the carrier signal to the received signal and apply LPF. In order to do so you can use simple multiply functions in labview. For higher applicaitons like RF you can use modulation toolkit instead.

Good Luck

lab

[Williamx]

Hi Lab_boy, sounds like a good idea, but I'm using DASYLab am trying to figure out with the tools it comes with how I could accomplish this. We'll be getting LabVIEW, but that item won't be ordered for a few months yet.

I also noticed that LabVIEW would be the preferred way to go if I could now.

[lab_boy]

Hello Bill,

I have never used DasyLAB, I would suggest you post this on DasyLAB forum, they are pretty active there.

goodluck

[Williamx · Accepted solution]

Although I wasn't able to demodulate the signal, using the FFT I was able to quickly isolate the frequency since my input was a clean sine wave.

Thanks to CJ for working up an earlier example that lead me down the path to implement the solution!