Re: calculate SNR and watch a binary file

[Rob Mahurin]

On Mar 26, 2009, at 6:18 PM, Markus Feldmann wrote:
> Rob Mahurin schrieb:
> > These files came from some analog-to-digital converter?  If you look
> > at them with hexdump, there is stuff that looks like data only in the
> > first 200 bytes or so.  The rest of the file looks likes zeros and
> > the occasional 0x80bf.  I wouldn't expect the data read from these
> > files to have a meaningful Fourier transform.
> >
> > Cheers,
> > Rob
> The data can be watched with my method, but not be plotted.
> I do not know how to collect the complex values and bits ?
>
> Ok, here is a clipping from the data at the beginning:
>         0 +     0i
>         0 +     0i
>        -1 +     0i
>         0 -     1i
>       -13 +     2i
>        65 -    32i
>      -183 +    98i
>       412 -   233i
>      -831 +   478i
>      1572 -   918i
>     -3050 +  1745i
>      8314 -  4139i
>    -12548 -  5491i
>      3899 + 10329i
>      3523 -  2748i
>     -1791 +  1379i
>       951 -   738i
>      -484 +   378i
>       219 -   176i
>       -84 +    69i
>        19 -    20i
>         0 +     0i
>         0 -     1i
>         0 +     0i
>         0 -     1i
>         0 +     0i
>         0 -     1i
>         0 +     0i
>         0 +     0i
>         0 +     0i
>         0 +     0i

This is a plausible decoding of your data file.  To plot just the  
real or imaginary part of a vector v, do plot(real(v)) or plot(imag 
(v)).  plot(v) will show points in the complex plane.

If these are already Fourier components, plot( abs(v).^2 ) will show  
your power spectrum.  There is a broad peak centered around the 15th  
frequency bin.

If this is supposed to look like a sine wave, you have made a mistake  
I don't understand.

Cheers,
Rob

--
Rob Mahurin
Department of Physics and Astronomy
University of Tennessee                 865 207 2594
Knoxville, TN 37996                     address@hidden