Re: [Discuss-gnuradio] GNU Radio and USRP baseband demodulation/decoding

[Johnathan Corgan]

On Thu, Feb 5, 2009 at 10:59 AM, Einar Thorsrud <address@hidden> wrote:

> How will the synchronization and carrier recovery function on my
> baseband signal as there really is no carrier left after the down
> conversion? My specific signal is down converted from 5.8 GHz to
> baseband from an RF front end, which is not controlled by GNU Radio at
> all. Would the blocks you mentioned function with the baseband signal if
> the center frequency is specified to be 0 Hz?

Even after downconversion to 0 Hz IF, there will be a residual carrier
based on the frequency stability of the transmitter and receiver.  The
Costas loop block will track out this carrier until its output is
truly baseband.  Due to the difference in crystal timebases between
the transmitter and receiver (or relative motion causing Doppler),
there will also be a timing error, with the M&M block will handle.

Johnathan