Forum: GNU Radio Intermediate Frequency of RFX2400

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051a38020a2f15e4604075dfc309b3aa?d=identicon&s=25 Yong J. Chang (Guest)
on 2009-01-29 01:16
(Received via mailing list)
Hi all,

Now I'm confusing intermediate frequency of RFX2400. I cannot find any
references about that.
As I know so far, RFX2400 converts carrier frequency(we selected it on
python script) band freq to 10Mhz intermediate freq. This 10Mhz signal
is
passed to FPGA. Therefore, DDC frequency is fixed on 10Mhz. Is it right?

Any help is appreciated.

Y.C
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745d8202ef5a58c1058d0e5395a78f9c?d=identicon&s=25 Eric Blossom (Guest)
on 2009-01-29 02:22
(Received via mailing list)
On Wed, Jan 28, 2009 at 04:09:54PM -0800, Yong J. Chang wrote:
>
> Y.C

The RFX boards are quadrature direct conversion.  We feed them complex
basebase within a few MHz of DC.  The DDC/DUC are used for fine tuning
since
the VCO on the daughterboards have a non-zero step size.

You can see what's happening by examining the result from u.tune().

I highly recommend the USRP FAQ:

  http://gnuradio.org/trac/wiki/UsrpFAQ
  http://gnuradio.org/trac/attachment/wiki/UsrpFAQ/U...

See also the nice diagrams on this page:

  http://gnuradio.org/trac/wiki/UsrpRfxDiagrams

Eric
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