H
i Marcus,
                  I got it. It is a case of bandpass sampling. .Thank you.


On Fri, Jul 5, 2013 at 6:12 PM, Marcus D. Leech <mle...@ripnet.com> wrote:

> **
> On 07/04/2013 11:51 PM, Karan Talasila wrote:
>
>  Hi Josh,
>               can you explain how and why the frequency translation
> occurs? secondly when the same basic tx chip is used on a  usrp N210, the
> translation occurs at 50Mhz and after. So for USRP N210, the entire range
> from 0-250 Mhz is represented by alternating between -50Mhz to +50Mhz. Why
> is it that way?
>
>  The BASIC_RX and LF_RX have no downconversion hardware in them at all.
> They are basically just "buffers" for the ADCs.  The BASIC_RX has an
>   analog reponse that starts to fall off at about 250Mhz, which is why
> it's rated to 250Mhz.
>
> In the USRP1/B100/E1XX systems, the sampling clock is at 64MHz by
> default.  That means the first aliases start to show up at the 1st Nyquist
>   frequency of 32Mhz (half of sample rate).   Similarly in the N2XX, which
> a 100MHz sampling clock, those aliases start to show up at 50Mhz.
>
> My suggestion would be to look into so-called bandpass sampling, and also,
> importantly, Nyquist Sampling Theorem.
>
>
> --
> Marcus Leech
> Principal Investigator
> Shirleys Bay Radio Astronomy Consortiumhttp://www.sbrac.org
>
>
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>


-- 
Regards
Karan Talasila
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