On Tue, Nov 21, 2006 at 06:06:58PM -0600, Shravan Rayanchu wrote: > Hi, > > I am new to DSP, so I am finding it a little difficult to understand > exactly whats going on in the usrp_spectrum_sense.py code. When I > print out m.data[0], m.data[1] along with m.center_freq, this is what > I get: > > ./usrp_spectrum_sense.py 2412M 2444M > > Using RX d'board A: Flex 2400 Rx > gain = 45.0 > 2413500000.0 10906340.0 4703766.5 > 2416500000.0 5325887.0 4675695.0 > 2419500000.0 1110628864.0 726685696.0 > .... > > I understand that output of the block gr.fft_vcc would be the FFT of > the signal; And then we do a c2mag to get the power spectrum .. > > My question is: If my center frequency is say 2413500000.0 (first line > of the output), how do I measure the power on that frequency? Is it > proportional to data[0]? (The comments say that data[0] is DC .. is > this DC relative to the center frequency?) > > What frequency does the bin data[1], data[2] etc represent? Is this > dependent on the ADC sampling frequency? > > Thank you for the help. > > Regards, > Shravan
I suggest that you take a look at the docs on www.fftw.org. Our fft block uses FFTW to do the work, and the output is exactly as they specify. http://www.fftw.org/fftw3_doc/The-1d-Discrete-Fourier-Transform-_0028DFT_0029.html#The-1d-Discrete-Fourier-Transform-_0028DFT_0029 For a good intro to DSP, see "Understanding Digital Signal Processing" by Richard Lyons. ISBN 0131089897 Eric _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
