On 01/20/2011 10:22 PM, James Jordan wrote: > Marcus, Thanks for reply. > That is make sense, so the point become how to convert the signal to > baseband. Oh, that's relatively easy--you multiply it with a complex signal at the same frequency--that's exactly how it's done in hardware, and it works equally-well in software.
The Gnu Radio channelizer likely is more sophisticated than that, using different mathematical tricks to improve efficiency, etc. When you multiply two sinusoids of Xhz and Yhz, you end up with a mixed sinusoid-- Xhz+YHz and XHz-Yhz. In direct-conversion, you mix (multiply) it with a signal of the same center frequency, and you get the baseband frequencies, but since this is baseband, you need to use complex representation, otherwise the + and - frequencies "fold" around each other. -- Principal Investigator Shirleys Bay Radio Astronomy Consortium http://www.sbrac.org _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
