Re: [Discuss-gnuradio] hi all, can I use one RX receive a wideband signal and then seperate it to many narrowband signals

[Marcus D. Leech]

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