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

salman dinani salmandinani at gmail.com
Tue Feb 14 02:38:20 EST 2012


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??


Regards

Salman Dinani

On Mon, Feb 13, 2012 at 6:10 PM, Mike McLernon
<Mike.McLernon at mathworks.com>wrote:

>  Hi Salman,****
>
> ** **
>
> The Simulink SDRu driver is built on top of the UHD driver, so any
> limitations imposed by UHD will be encountered in Simulink.  Also, note
> that the SDRu Receiver block supports int16 complex data outputs.  That
> math implies a max rate of 25 Msps ( (16 bits/sample real + 16 bits/sample
> imaginary) * 25 Msps = 800 Mbps.****
>
> ** **
>
> Mike****
>
> ** **
>
> ** **
>
> *From:* usrp-users-bounces at lists.ettus.com [mailto:
> usrp-users-bounces at lists.ettus.com] *On Behalf Of *salman dinani
> *Sent:* Sunday, February 12, 2012 11:01 PM
> *To:* Ian Buckley
> *Cc:* usrp-users at lists.ettus.com
> *Subject:* Re: [USRP-users] SBX daughtercard bandwidth problem..!!****
>
> ** **
>
> Thanks Josh and Ian Buckley....:) So it means:****
>
> 1. I cannot set the decimation or interpolation to "1" in simulink SDRu
> block? or in other words i        cannot get the sampling rate of 100
> MSPS?? :( ****
>
> ** **
>
> 2. Is there any way using Simulink SDRu block??****
>
> ** **
>
> Regards ****
>
> ** **
>
> Salman Dinani****
>
> On Mon, Feb 13, 2012 at 2:06 AM, Ian Buckley <ianb at ionconcepts.com> wrote:
> ****
>
> Clearly I needed more coffee!
> You confused me there referring to it as a 16bit mode rather than 8bit
> complex.****
>
>
> On Feb 12, 2012, at 9:47 AM, Josh Blum wrote:
>
> >
> >
> > 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
> >>>
> >>> _______________________________________________
> >>> USRP-users mailing list
> >>> USRP-users at lists.ettus.com
> >>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
> >>
>
>
> _______________________________________________
> USRP-users mailing list
> USRP-users at lists.ettus.com
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com****
>
> ** **
>
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