Re: [Discuss-gnuradio] Help : Is this right that the daughterboard passes data to the usrp board in the I and Q format.

[Marcus D. Leech]

On 25/04/2011 8:34 AM, ton ph wrote:
> Hi marcus
>       thanks for immediate reply and your guide was  very helpful from 
> my side ... Now the question is  ,
>  suppose,  i have 12 bit  200 mhz adc , and i do not want to reduce my 
> processing bit , as per the instruction from your side it could be
> hard to process in my i5 , 4Gb ddr3 configuration computer and also i 
> am not aware  of the IF bandwidth which might require to make
> the bandwidth  process instantly ( simultaneously ) . Will gnuradio be 
> able to support the instantaneous processing of the 100Mhz bandwidth,
> I have a bit doubt as i learnt that gnuradio can support 8Mhz only.
>
> Thanks , and i highly apologize if my post is a bit out of track or 
> may be called a bit illogical ....
>
> Thanks marcus.
I process 25MHz bandwidth from a USRP2 with my Radio Astronomy 
applications, on a 6-core AMD Phenom II X6 running at 3.2GHz.

The "8MHz" figure you quote is likely from the original USRP--nothing to 
do with Gnu Radio, per se.  The USRP1 has a maximum
  bandwidth of 8MHz unless you drop down to 8-bit samples.

The computational load of a signal flow-graph is proportional to 
bandwidth X complexity.

If you want to process 200Msps, with full 12-bit resolution, you'll need 
to find some other host interface than 1GiGe--you'd likely
  need to go to a 10GiGe interface.

And while Gnu Radio "scales" arbitrarily, there are limits to the degree 
to which you can optimize a flow-graph for performance.
  The "Lego brick" approach to constructing processing graphs isn't 
optimal if really-high performance and low-latency are
  important to you.  In order to process 200Msps, you'd likely need to 
hand-craft your signal processing chain, and carefully
  parallelize it in an optimal way.  No way are you going to be able to 
do this on a single-processor machine.

Further, as you point out, the post-mixer bandwidth of the USRP-family 
daughtercards is limited to much less than 50MHz, in order
  for there not to be an aliases when sampled at the 100Msps rate of 
the ADC on the USRP.