[USRP-users] Capturing signals at the carrier
Marcus D. Leech
mleech at ripnet.com
Mon Sep 30 18:18:45 EDT 2013
On 09/30/2013 04:47 PM, Cochenour, Brandon M CIV NAWCAD, 4.5.6 wrote:
> After some further experimentation...I notice that not all carrier frequencies result in the DC component being removed.
> For example....using the N210 with WBX...
> At a 50 MHz carrier...I can modulate a single tone all the way down to about 200 Hz with no issue. Between 100-200 Hz...I observe all sorts of weird harmonics. At 100 Hz...everything is fine. Between 1-100 Hz...strange harmonics. And then a 0 Hz...a clear spectral peak at DC.
> However at certain other frequencies....I'll get no DC through at all.
> I also note that it doesn't matter if I use the TX side of the WBX as my input...or if I try to tune an external source to get as close to the USRP LO as I can. Some center frequencies work. Others don't.
> There doesn't seem to be much rhyme or reason as to why certain frequencies work, and others don't. Should there be?
> USRP-users mailing list
> USRP-users at lists.ettus.com
The amount of DC offset and gain and IQ imbalance produced in the PLL is
highly dependant on the tuned frequency.
Shirleys Bay Radio Astronomy Consortium
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