niUSRP 1.2 / USRP N210 / beat frequencies LO

[santiago22]

Hi,

I made a Labview 2012 program based on some examples of the ni USRP 1.2 software, for being executed in my USRP N210. The objective of my program is to measure a signal, that right now is generated by a RF signal generator, after doing an fft plot of it, and show it in a graph chart. I also want to show a plot with the values of the max in dBs of the signal and its contiguous bins. The problem that i have is that i have some type of 'continous' signal that doesnt let me focus on the one signal that i want to measure and work with. I have read about some type of beat frequencies generated by the LO of the USRP n210 motherboard, but im not completly sure about that. I also want to note that i have the tvrx2 daughterboard installed. Any question, answer or recomendation will be very welcome! Thanks

Santiago Mariño Cambeiro

[santiago22]

Hi,

I made a Labview 2012 program based on some examples of the ni USRP 1.2 software, for being executed in my USRP N210. The objective of my program is to measure a signal, that right now is generated by a RF signal generator, after doing an fft plot of it, and show it in a graph chart. I also want to show a plot with the values of the max in dBs of the signal and its contiguous bins. The problem that i have is that i have some type of 'continous' signal that doesnt let me focus on the one signal that i want to measure and work with. I have read about some type of beat frequencies generated by the LO of the USRP n210 motherboard, but im not completly sure about that. I also want to note that i have the tvrx2 daughterboard installed. Any question, answer or recomendation will be very welcome! Thanks

Santiago Mariño Cambeiro

[lf_fr]

Hi Santiago,

Most likely what you are observing is the so called "LO leakage".

A typical workaround is to shift the LO frequency outside the frequency band that is monitored, keeping

in mind that you are restricted by the A/D bandwidth (check out

the USRP property node for an item called LO Frequency [1]).

As a side node, regarding your application, I've seen that you are using a laptop.
Be aware that the achievable sampling rate depends on the "quality" of the embedded NIC and the driver

parameters (it all depends on the bandwidth you are targeting).

L

[1] http://zone.ni.com/reference/en-XX/help/373380B-01/usrppropref/pniusrp_lofrequency/