Re: [Discuss-gnuradio] USRP2 - Many Narrowband

[Eric Blossom]

On Mon, Jan 05, 2009 at 01:44:53PM -0800, Matt Ettus wrote:
> Ryan Pape wrote:
>> All:
>>  I'm currently trying to extract a relatively small number of  
>> narrowband channels out of about 10mhz.  With USRP1, I can get two  
>> channels easily by using both sets of DDCs.  In some instances, I can  
>> successfully use a filterbank, however at 12.5khz channels, I quickly  
>> run out of horsepower if I don't keep the decimation high enough,  
>> which does not always let me cover the swath of RF I need.  Are there 
>> any other possibilities with the new USRP2 hardware to implement more 
>> DDCs in the firmware to do more of this work on the USRP side?  Any 
>> other thoughts in general?
>
> You could implement more DDCs in the USRP2, but it makes more sense to  
> use filterbanks in software.  It may take something more complicated  
> than a straight forward filterbank across the whole bandwidth.  You  
> might want to do it in a few steps.  For example, do a filterbank to get  
> you 16 channels of ~500 kHz apiece, and then do smaller filterbanks on  
> only those 500kHz bands have signals of interest in them.
>
> Matt

The filterbank in the tree was done quick and dirty.
There's lots of room for improvement. (e.g.,  coalescing many of the
intermediate blocks.)

Eric