On 01/02/2019 08:06 PM, Milos Milosavljevic via USRP-users wrote:
Dear All,
I was wondering if somebody could clarify a couple of issues that I
have with the UHD and N200 USRP. I am using the latest version of the
software.
I am generating a single tone to be transmitted with N200 (WBX board)
using uhd_siggen as:
/
/
/uhd_siggen -g 15 -s 500000 -m 0.5 -f 402000000 --lo-offset 10000000
-x 50000 --sine/
1) I can see quite a strong spurs at 10MHz and 20MHz freq offset from
the carrier? (I am not using any external filtering)
Define "quite strong".
2) If I modify the siggen to use
*float((uhd.tune_request(f,lo_offset))* instead of just
*uhd.tune_request(*f,lo_offset*)* the signal with constant source is
much cleaner. However, if I modulate the carrier with a sine source
another set of spurs appear very close to the carrier. This is not
though the case when float is not used (but spurs at 10 and 20MHz are
still present).
Why does the *float *with *tune_request *make such a big difference?
Well, looks like you're casting a tune_request_t to a float, which
means that the offset instruction will likely get ignored, which changes
whether the DUC comes into play or not.
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