[USRP-users] SBX daughtercard bandwidth problem..!!

Josh Blum josh at ettus.com
Tue Feb 14 04:57:59 EST 2012



On 02/13/2012 11:38 PM, salman dinani wrote:
> Hi,
> 
> I have attached a picture which shows my problem that even I set the
> decimation factor to 1, in order to get the sample rate of 100 MSPS, but
> the device value remains at 4, which means :
> 
> RF_Font_end_Sample_rate= 100e6/4=25e6,
> 
> which means that only waves up to Max 12 MHZ can be sampled..
> 
> we have to buy more daughter boards for our application which require
> 100MSPS and BW of 40MHz and we bought this product because of its these
> features but unfortunately we are not able able to use it that way.
> 
> 1. Am I write in this conclusion? Am I configuring the card wrong or it is
> the inherit problem?
> 2. So than what is the use of ADC of 100 MSPS, if we can use it only up to
> 25MHz??
> 3. It is written on application notes that Bandwidth is 40 MHZ, but why its
> is only 12MHz??
> 

Salman,

I don't know what to say. SBX really has a 40 MHz filter. Filter
bandwidth and sample rate are different things.

I'm sorry SDRu doesn't yet support complex-int8 samples over the wire.
I'm sure the feature will come soon. In the meantime you can code to the
UHD API and/or gnuradio to take advantage of said feature.

Regardless, thats a serious amount of data you want to take into the PC.
Be prepared for code profiling and optimization. If the link rate or
host processing becomes a bottleneck, move processing into the FPGA.

-Josh




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