You can do this by building an image reject mixer. The description is rather lengthy, but an excellent article by Rick Campbell, "High Performance Single-Signal Direct Conversion Receiver", was published in the Jan 1993 issue of QST. Contact www.arrl.com I believe they can provide you with a copy of the article. This type of mixer does exactly what you have described Hope this helps. If you need more detail. You can contact me at kizerian@sarcos.com or kizerian@qwest.net on weekends. Bruce Kizerian ----- Original Message ----- From: "R. Michael O'Bannon" To: Sent: Thursday, March 22, 2001 9:47 AM Subject: [OT]:Mathematics of pitch shifting > Here's a question for those familiar with DSP. Any help would be > appreciated. > > I'm working on a project to shift the pitch of a complex waveform in > real time. The pitch shift will always be upward -- that is, the > frequency of the output will always be higher than the original. > The size of the shift in Hz needs to be determined by a local > frequency source and may change rapidly. From ham radio days, I > remember that this is similar to generating single sideband signals. > A local oscillator is mixed with the waveform to generate sum and > difference frequencies. The signal could be shifted 10 Hz , by > mixing it with a 10 Hz sine wave and filtering out the lower > sideband. What I would like to do is eliminate the need for > filtering out one sideband. > > If both signals are digitized, multiplying the two together and > normalizing the result will produce the two sidebands (both sum and > difference frequencies). Unfortunately, this is where my math fails > me. Years ago one of the Radio Amateur's Handbooks published a > formula for generating a single sideband using fairly simple math > and trig functions, but that Handbook is long gone. Does anyone > know what the formula is or where I might find it? I suspect that > this is a common problem in DSP work, but I am a real novice in that > black art. > > Thanks, > Michael > > -- > http://www.piclist.com hint: To leave the PICList > mailto:piclist-unsubscribe-request@mitvma.mit.edu > > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.