On 04/26/2013 12:56 PM, Marcus D. Leech wrote:
On 04/26/2013 12:52 PM, vegihat vegihat wrote:
i use the following command to capture some samples of noise
uhd_rx_cfile -a serial=4759a751 -N 100000 -f 2.48G --samp-rate=2M
noise.dat
then using matlab i read the samples
y=read_complex_binary ('noise.dat');
and i do plotfft
plotfft(y,2000000)
the plot shows a peak near the center. I don't know why. what could i
do on the samples y so that the peak not appeared?
i attach the figure of plotfft
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That is the residual DC offset.
UHD allows you to use offset tuning to arrange for the DC offset to be
outside your passband, but you'd have to modify uhd_rx_cfile to use that
feature of UHD.
http://files.ettus.com/uhd_docs/manual/html/general.html#two-stage-tuning-process
--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
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Actually, just noticed that uhd_rx_cfile now has a --lo-offset option,
so you don't even need to modify the code, just specify the LO offset --
typically I set
it to a little bit more than half my sampling bandwidth.
--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
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