I am new at gnuradio companion and USRP and I am a little bit confused with UHD:USRP Sink block. I am trying to build an FMCW radar in USRP N210 with CBX40 daughterboard. I want to generate a sweep from 2GHz to 3GHz. First, I’ve generated the sweep in baseband which I want to upconvert to my desired frequency range. My grc diagram is the following:

At the output of the Hilbert block I can see the baseband frequency sweep. However, I connect my USRP to an Spectrum Analyzer and I only see a tone at 2.2GHz (the Center Frequency I set in the UHD:USRP Sink block).

I expected the frequency at the output of my usrp to be the sum of the baseband frequency and the center frequency.

Is there anything I am misunderstanding? Should I modify any of the settings?

Thank you in advance,