Re: [Discuss-gnuradio] Help : Where is the demodulation blocks implemented in gnuradio [ GMSK,PSK etc].

[Marcus D. Leech]

On 07/04/2011 10:34 AM, ton ph wrote:
> Hi guys ,
>  I Just want to confirm a thing regarding the demodulation of the 
> digital dat in the gnuradio as the signals are received from the usrp. 
> The doubt are,
>  1. Where is the demodulation is implemented in the gnuradio .
>  2. What demodulation is implemented by default in the urp_rx_cfile ...
> please do help me someone in clearing my doubts .
>
> Thanks
Gnu Radio is a generic digital-signal-processing framework. Which 
includes *many* pre-built processing blocks, including demodulators
  and modulators, correlators, detectors, etc, etc.

There is no *default* demodulation scheme anywhere in the basic 
architecture, and usrp_rx_cfile is used to simply copy samples as they
  come off the USRP hardware into a file.

The USRP hardware doesn't do any demodulation--the signal you see 
delivered to the host PC is just filtered/decimated baseband
  samples as they come off the ADC, appropriately scaled for use inside 
Gnu Radio.  The USRP hardware doesn't know anything
  about modulation or demodulation, per se.  All of that is the 
responsibility of the host software.  Correspondingly, the transmit
  side of the USRP hardware doesn't *know* anything about modulation, 
either.  It is entirely up to the host software to provide
  appropriately-modulated samples for the hardware to dutifully turn 
into analog signals and then (usually) up-convert to the
  desired RF band of interest.  Generally, the host interface operates 
in "baseband" mode--the (complex) samples are centered at DC.

Cheers