Re: [Discuss-gnuradio] Spectrum Sensing

[Shravan Rayanchu]

Does that mean 8Mhz is the max. width of spectrum I can sense? But I
remember reading on some post that we can sense spectrum upto +/-15MHz
from the carrier frequency. (i.e. a chunk of 30 Mhz). Which one of the
above is correct? What puts a limit on the maximum amount of spectrum
we can sense?

Also, the in the program "usrp_spectrum_sense.py [options] min_freq
max_freq", is there a limit on (max_freq - min_freq)?

Thanks,

Shravan.





On 11/2/06, Johnathan Corgan <address@hidden> wrote:
> On Thu, 2006-11-02 at 15:53 -0600, Shravan Rayanchu wrote:
>
> > I was going through some gnuradio documentation (on comsec.org wiki)
> > which says "...16-bit I and 16-bit Q data (complex), resulting in 8M
> > complex samples/sec across the USB (32 Mbps max. data rate). This
> > provides a maximum effective total spectral bandwidth of about
> > 6MHz...".
> >
> > By Nyquist criteria, should not this be 4 Mhz?
>
> This would be true for 8M *real* samples per second of a signal.
> However, when sampling in quadrature (complex sampling), you are
> creating 16M independent samples/second, and the Nyquist frequency is
> half that, or 8 MHz.
>
> I'm not sure where the 6 MHz reference comes from, except that that is
> also the IF bandwidth of the TV tuner module GNU Radio used to use (and
> the TVRX board that the USRP uses), so with these you'd get an
> "effective" spectral bandwidth of 6 MHz.
>
> --
> Johnathan Corgan, AE6HO
> Corgan Enterprises LLC
> address@hidden