Re: [Discuss-gnuradio] Spectrum Sensing

[ldoolitt]

Shravan -

On Thu, Nov 02, 2006 at 03:53:35PM -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?

When you have both I and Q, we have sign information on the
frequency, so the full range of -4 MHz to +4 MHz is 8 MHz.
Of that, 75% is valid data, the rest includes aliases and
shouldn't be trusted in most circumstances.

> Also, I found this note
> at some other place which said that we can sense spectrum upto +/-
> 15MHz from the carrier frequency. Which one of the above is correct?

Both.  The choice of _which_ 6 MHz band can be adjusted
digitally.

> And what is bottleneck for maximum amount of spectrum we can sense at
> one time, is it limited by the usb bus speed?

Yes.

    - Larry