[USRP-users] [Discuss-gnuradio] Bandpass Sampling

Ian Buckley ianb at ionconcepts.com
Tue Dec 9 11:41:37 EST 2014


Block diagram USRP N210 + WBX:

http://www.ni.com/white-paper/app/largeimage?lang=en&imageurl=%2Fcms%2Fimages%2Fdevzone%2Ftut%2FUSRP_Advanced_Diagram_smaller.png

On Dec 9, 2014, at 8:24 AM, Marcus Müller via USRP-users <usrp-users at lists.ettus.com> wrote:

> Hi Richard, 
> it's a 300+-page PDF file, which works quite well on any computer that I tried -- maybe you need to wait a second for your PC to load that document?
> 
> It doesn't contain a block diagram of the WBX, however.
> 
> Greetings,
> Marcus 
> 
> On 12/09/2014 02:00 AM, Richard Bell wrote:
>> I've seen the the UHD manual but not the performance measures doc. It is
>> not opening for me. If it has a block diagram of the WBX board, then that
>> is what I was looking for.
>> 
>> There is no more information I need at this time. Your previous answer was
>> helpful and what I was looking for.
>> 
>> Yes you can move this to the usrp list.
>> 
>> Thanks again,
>> Rich
>> 
>> On Mon, Dec 8, 2014 at 12:24 PM, Marcus Müller <marcus.mueller at ettus.com>
>> wrote:
>> 
>>>  There's so much Marcus in here ;) so here's my answer: usually, you'd use
>>> the USRP+WBX as direct conversion receiver, not an IF one.
>>> 
>>> Regarding WBX documentation: have you seen the performance measurements
>>> [1], and the UHD manual [2]?
>>> 
>>> Is there some specific information you're missing?
>>> 
>>> Best regards,
>>> Marcus
>>> 
>>> PS: if you'd agree, I'd like to shift this discussion to
>>> usrp-users at lists.ettus.com .
>>> 
>>> [1] http://files.ettus.com/performance_data/wbx/
>>> [2] http://files.ettus.com/manual/page_dboards.html#dboards_wbx
>>> 
>>> 
>>> On 12/08/2014 08:57 PM, Richard Bell wrote:
>>> 
>>> I think Marcus answered my question. Thank you.
>>> 
>>> On Mon, Dec 8, 2014 at 11:53 AM, Richard Bell <richard.bell4 at gmail.com> <richard.bell4 at gmail.com>
>>> wrote:
>>> 
>>> 
>>>  I'm apologize. I am using a WBX card.
>>> 
>>> I forgot to mention that I've been looking for a datasheet for the WBX,
>>> but all I can find is the PCB schematic doc on the ettus website which
>>> isn't very useful. So I don't know what the IF frequency coming out of the
>>> WBX is. Does the WBX tune itself given the UHD source settings so that the
>>> IF it produces is proper for the USRP ADC?
>>> 
>>> Rich
>>> 
>>> On Mon, Dec 8, 2014 at 11:28 AM, <mleech at ripnet.com> <mleech at ripnet.com> wrote:
>>> 
>>> 
>>>   The N2xx series use a fixed sample rate, so there's no "deciding what
>>> sample rate to use based on Fc".
>>> 
>>> There's also the analog bandwidth of the ADC to consider.  If you aren't
>>> going to use a downconverter card, then the analog bandwidth of the ADC
>>> will start to roll-off at some point, so even if you narrowband filter your
>>> input signal to remove aliasing possibilities, you will end up in the
>>> roll-off skirts of the analog bandwidth of the ADC.
>>> 
>>> Is there some reason not to use a downconverter card, like the WBX for
>>> your application?
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> On 2014-12-08 14:23, Richard Bell wrote:
>>> 
>>>   I have a binary FSK signal centered at 300 MHz with 160 kHz offset
>>> peaks from the center freak. Therefore the lowest signal frequency of
>>> interest is 300-0.16 = 299.84 MHz and the highest is 300.16 MHz.
>>> 
>>> I know the maximum sampling rate of the USRPN210 ADC is 100 MSPS. If the
>>> USRP uses that sample rate of 100 MSPS, it will alias my signal onto itself
>>> in an unwanted manor.
>>> 
>>> My question is, how does the USRPN210 decide what sample rate to set the
>>> ADC to? Is it a function of both the center frequency and the sample rate
>>> setting of the UHD source block?
>>> 
>>> Thanks,
>>> Rich
>>> 
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>> 
>> 
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