Re: [Discuss-gnuradio] Bandwidth of XCVR 2450 Daugtherboard

[Marcus D. Leech]

On 28/09/2011 2:32 PM, Konstantinos wrote:
> Thanks for your reply.
>
> However, I am a little bit confused since in your reply you mention that these
> are programmable low-pass filters which operate at baseband, while in the code
> the associated comment says that this is the bandwidth of the bandpass filter on
> the board. Secondly, why are these baseband filters? These are on the
> daughterboard so I would expect them to operate on the intermediate band, since
> the daughterboard converts complex IF to Real RF. Please let me know where I get
> this wrong.
>
> Thank you for your time again.
>
> BR,
>
> Konstantinos
Most of the daughtercards convert to/from complex-baseband to/from real 
RF.  The analog filters operate at baseband, and are therefore
  low-pass filters.

There are exceptions--the TVRX and TVRX2 use a non-zero IF.  But all the 
other daughtercards use complex-baseband.

So, in complex baseband, if you want a total bandwidth of 40MHz, what 
you're actually asking for is -20Mhz to +20Mhz.  Which means that
   I and Q are both low-pass filtered to 20MHz.