Re: [Discuss-gnuradio] USRP2 Noise figure and Phase noise measurement methods

[Per Zetterberg]

Correction:

SNR = 174 - log10(BW) + Pin - NF,

BR/
Per


On Mon, 2010-10-04 at 09:29 +0200, Per Zetterberg wrote:
> On Sun, 2010-10-03 at 15:30 +0200, Jorge Miguel wrote:
> > Hi all!,
> > 
> > I am going to measure both parameters, noise figure and phase noise of
> > my USRP2+XCVR2450 transceiver.
> > After some reading about different methods of measuring them I have
> > some questions.
> > 
> > Phase noise. 
> > I read that in the lack of a Signal Source Analyzer (SSA) the most
> > spread method of measuring it is with the delay line technique. Is it
> > the right way to measure the phase noise in the USRP? Has anybody of
> > you done it before? 
> > 
> 
> I just measure a CW and do an fft. Results: See the following post:
> 
> http://lists.gnu.org/archive/html/discuss-gnuradio/2010-03/msg00299.html
> 
> > Noise figure.
> > The standard way of measuring it seems to be the Y-Method using a
> > noise source connected to the DUT and then measuring the output power
> > of the DUT when the noise source is on and off. However as I
> > understand it, in this case the USRP2 is not a two port device. It is
> > just a receiver. Is it valid to measure the USRP2 power with software?
> > (usrp2_fft.py for example, as I have read in another mailing list
> > posts)
> > 
> 
> What I do is to insert a CW with known power and then estimate the SNR.
> The NF can then be calculated from
> 
> SNR = -174 + log10(BW) + Pin + NF,
> 
> where SNR and NF are in dB, Pin in dBm and BW in Hz. The BW is the noise
> bandwidth. Roughly it is sample_freq/2. 
> 
> 
> > What are the range of values I should expect to understand I have made
> > a good measurements?
> 
> Look at the data-sheet of the MAX2829. Note that at high Pin your SNR
> will be dominated by the distortion and the NF will seem larger than in
> actually is.
> 
> BR/
> Per
> 
> 
> _______________________________________________
> Discuss-gnuradio mailing list
> address@hidden
> http://lists.gnu.org/mailman/listinfo/discuss-gnuradio