A question about digital upconversion, but at the core its about quadrature modulation. I have real I and Q data streams at an IF of 20 MHz, what do I need to do to "combine" these messages into a single signal at 20 MHz?
Digital upconversion, forming quad mod passband signal
Started by ●September 12, 2007
Reply by ●September 12, 20072007-09-12
What you want is - baseband I stream, multiplied with sin(2 pi 20 MHz t) - baseband Q stream, multiplied with cos(2 pi 20 MHz t) - add those two What you've got is - baseband I stream, multiplied with sin(2 pi 20 MHz t) - baseband Q stream, multiplied with sin(2 pi 20 MHz t) ??? If so, you need to turn sin into cos. For example - Use a 90 degree phase offset when generating one stream - Use a Hilbert filter - Downconvert / filter / upconvert - simply delay (approximation, the wider the modulation BW the worse) - ... -mn
