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) 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? I verified the above with my own flowgraph as well using a signal source and USRP sink blocks. Could anybody shed some lights on this please? Many thanks, Milos P.S. I wish I could post some spectrum plots but due to message size limit I am struggling to reduce the pics size.
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