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

Josh Blum josh at ettus.com
Sun Feb 12 12:47:04 EST 2012



On 02/12/2012 09:36 AM, Ian Buckley wrote:
> Josh, 
> It's possible you didn't have your Sunday morning coffee yet, or  possibly that the laws of Physics have been shattered...
> but did you really intend to state that you can now receive 16bits @ 50Msps in UHD...because Cisco would like to offer you a job if so :-)
> I'm assuming you intended to say 8bits at 50Msps.......or is it not a complex sample stream in this new mode?

sorry, no coffee yet, but the math seems solid

1 byte real, 1 byte imaginary = 16 bits per sample (complex baseband)

16 bits per sample * 50 Msps = 800 Mbits per second, which is well
within gigE rate of 1000 Mbits per second.

-Josh

> 
> -Ian
> 
> On Feb 11, 2012, at 10:58 PM, Josh Blum wrote:
> 
>>
>>> 1. Am i write in this conclusion??
>>
>> Correct.
>>
>> However, it is possible to increase sample rate at the expense of
>> dynamic range. On the UHD master, you can receive 50Msps with 16 bit
>> samples. This feature is not yet a part of the SDRu driver.
>>
>>> 2. If yes, than why it is written in application notes tat it has BW of 40
>>> MHz??
>>
>> This is an analog bandwidth filter. You cannot receive signals outside
>> LO +/- 20Mhz due to the filter. Consider that some may tune the LO away
>> from the center frequency for various reasons.
>>
>>> 4. Why i am not able to set decimation or interpolation to 1.??
>>
>> The bandwidth bottleneck is the gigabit ethernet port. Given the recent
>> advent of 16 bit samples, a decimation of 2 is really the minimum.
>>
>> This is a user mod to burst 100Msps packets, which you may find helpful:
>> https://lists.gnu.org/archive/html/discuss-gnuradio/2011-03/msg00303.html
>>
>> -Josh
>>
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> 




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