Re: [Discuss-gnuradio] USRP2+WBX - How to use precisely an 8 MHz band?

[Vladutzzz]

Thank you all, for your replies!
I am a bit confused about the 10 rate decimation, which just gets one
halfband (the low rate one) - as explained in USRP2 FAQ. Does this affect
the power level that I will later measure?
I thought about using 8 which is also a multiple of 4, but it is a very
unfortunate fraction and I would like to keep as much as possible from the
original band, plus the 10 rate will also decrease the load on my processor.
So, is the 10 rate decimation in fact a good candidate for what I'm trying
to do or I'm better of using 8 with a 1.5625 rational resampler?
Thank you all.

Vlad.



Matt Ettus wrote:
> 
> On 11/11/2010 07:46 AM, Vladutzzz wrote:
>>
>> Dear all,
>> I am trying to receive with my USRP2 + WBX daughterboard a signal band of
>> precisely 8 MHz in order to measure it's power.
>> The problem is that since USRP2 has a 100 MSample/s sampling and I can't
>> just devide it by 12.5 to get the desidered 8 MHz band, I need
>> to use an FPGA decimation of 100 together with an interpolation of 8 in
>> order to get the desidered results
>> (I am not using decim 25 and interpol 2, because it is said in the
>> specification of USRP2 that both parameters have to be at least 4, and
>> multiples of 4, in order to get the full band).
>>
>> Is this the only way of going about this operation?
>>
>> Doesn't this eliminate too much usefull information?
>>
>> Please let me know if you would this in a different way!
>> Thank you for your time!
> 
> 
> I would suggest decimating by 8 or 10, and then filtering in software to 
> get the exact bandwidth you need.
> 
> Matt
> 
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