How can I use USRP as a noise generator?

[sam2013ni]

Hi everyone.

Does anyone know how can I use a NI USRP 2920 to generate white noise or impulsive noise at its Tx port?

(I am kind of new to this area and any help is appreciated)

Thanks.

[cade]

Hello,

I am assuming you are using LabVIEW to do this, correct? DO you have access to the help documentation for the NI-USRP driver? Within the help document there is a section called Software Fundamentals which has a section within it called NI-USRP Instrument Driver Programming Flow. This section shows you how to set up the USRP to transmit a signal. The default case is for an arbitrary array of data to be supplied to the Write Tx Data function. Instead you could use the output from the Uniform White Noise VI as the input for the Write Tx Data function. This should write the the white noise to the output of the USRP.

NI-USRP Instrument Driver Programming Flow:

http://zone.ni.com/reference/en-XX/help/373380A-01/usrphelp/programming_flow/

Uniform White Noise VI:

http://zone.ni.com/reference/en-XX/help/371361H-01/lvanls/uniform_white_noise/

I hope this helps.

Thanks,

[sam2013ni]

Hi Cameron.

Thanks for your reply. and I appoligize for the late reply. I was stuck in middle of measurements. 

Yes, I intend to use Labview with a N210 USRP. I used "niUSRP EX Tx Continuous Async Reconfig on the Fly.vi" and I replaced its sine wave sources with  "Gaussian White Noise Waveform.vi".

For my work, the frequency range of interest is between 1 MHz and 50 MHz. I run the above mentioned labview program and monitored USRP output with a Spectrum Analyzer. I noticed it increases the noise floor of my Spectrum analyzer and the amount of increase depends on the Noise Standard deviation I chose. There are two  questions here:

1. Is this the right way of producing CONTINUES noise source? (I mean using the VIs i mentioned above)

2. What should I do with Carrier frequency? should I leave it as 2GHz (which is out of my frequency range of interest)? I guess in any case when I use USRP the carrrier signal present at the TX port right?  Is there a way that I can get rid of it and just have noise?'

(one strange thing I found out is that, the carrier signal's amplitude  is not sensetive to the gain value I chose. So, what does that gain option do at the front pannel?)

[USBarnes]

Sam,

The way you are doing this sounds correct. Do you notice a difference if you try to change the carrier frequency? What spectrum analyzer are you using? I would expect the gain option to adjust the level of the transmission. Does the gain not change even if it is set before you run the VI?