Hi all, I need to do FM on a signal and the FM profile should be triangular. ie. the frequency vs. time plot of the modulated signal should have a triangular profile. How can I do this? All help will be greatly appreciated. Thnx in advance. Regards Apurva
Frequency modulation
Started by ●March 27, 2006
Reply by ●March 27, 20062006-03-27
apurva wrote:> Hi all, > > I need to do FM on a signal and the FM profile should be triangular. > ie. the frequency vs. time plot of the modulated signal should have a > triangular profile. > How can I do this? > > All help will be greatly appreciated. >* What technology are you doing this in? * presumably digital, but is it MatLab? Some specific DSP chip? generic C? COBOL? * if it's _not_ digital shouldn't you be on an electronic newsgroup? * Do you just need to generate a signal with a triangular FM, or do you need to design an FM modulator that will take _any_ input signal and then test it with a triangle wave? * Does your input signal have guaranteed upper and lower limits? * Does your input signal have guaranteed zero DC content (this can make a big difference in an electronic FM system; with guaranteed zero DC content you can use a phase modulator). In general, I would suggest that you make a good FM modulator in the technology of your choice. Then I'd make a triangle-wave generator (or pull one off the shelf), stick it's output into the modulation input of the FM modulator, and see if everything works right. If I really cared about making sure things worked I'd test it with more than just a triangle wave. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Posting from Google? See http://cfaj.freeshell.org/google/
Reply by ●March 28, 20062006-03-28
On Mon, 27 Mar 2006 10:06:48 -0800, Tim Wescott <tim@seemywebsite.com> wrote:>apurva wrote: > >> Hi all, >> >> I need to do FM on a signal and the FM profile should be triangular. >> ie. the frequency vs. time plot of the modulated signal should have a >> triangular profile. >> How can I do this? >> >> All help will be greatly appreciated. >> >* What technology are you doing this in? > * presumably digital, but is it MatLab? Some specific DSP chip? > generic C? COBOL? > * if it's _not_ digital shouldn't you be on an electronic newsgroup? >* Do you just need to generate a signal with a triangular FM, or do > you need to design an FM modulator that will take _any_ input signal > and then test it with a triangle wave? >* Does your input signal have guaranteed upper and lower limits? >* Does your input signal have guaranteed zero DC content (this can make > a big difference in an electronic FM system; with guaranteed zero DC > content you can use a phase modulator). > >In general, I would suggest that you make a good FM modulator in the >technology of your choice. Then I'd make a triangle-wave generator (or >pull one off the shelf), stick it's output into the modulation input of >the FM modulator, and see if everything works right. If I really cared >about making sure things worked I'd test it with more than just a >triangle wave.That's good advice Tim. Apurva should take great care in reviewing the math theory of FM. I'm specifically thinking about how the instantaneous phase of his "carrier" involves the integral of the modulating signal. See Ya', [-Rick-]
