Forum: GNU Radio Using USRP N200 at symbol rate 27.5 MSps

Ddfb5b6f5ff39383f36419b1d43d632c?d=identicon&s=25 Zooz Engineer (Guest)
on 2012-10-22 15:04
(Received via mailing list)
Dear All,

I have purchased 3 USRPs (N200) and set them up. I am intending to
implement a satellite receiver by connecting a board to the output of an
LNB (satellite dish). I am using the daughterboard DBSRX2  and I need to
used a symbol rate of 27.5 MSps ( compliant to the standard). For
testing purpose, I connected a USRP source to a graphical FFT sink and
ran GNURadio. Each time I run GNURadio, I receive a warning:

The hardware does not support the requested RX sample rate:
    Target sample rate: 27.500000 MSps
    Actual sample rate: 25.000000 MSps

I understand now that to achieve what I want, samples must be taken in 8
bit format in stead of 16. However, I have no clue of how to do this in
GNURadio. I changed the wire format to 8 bit but the warning keeps
showing up.

Any ideas or suggestions, please?

Thanks a lot.

Zooz
558c40b97bd1af8d912424757714bda9?d=identicon&s=25 unknown (Guest)
on 2012-10-22 15:20
(Received via mailing list)
On 22 Oct 2012 09:02, Zooz Engineer wrote:

> Dear All,
>
> I have
purchased 3 USRPs (N200) and set them up. I am intending to implement a
satellite receiver by connecting a board to the output of an LNB
(satellite dish). I am using the daughterboard DBSRX2 and I need to used
a symbol rate of 27.5 MSps ( compliant to the standard). For testing
purpose, I connected a USRP source to a graphical FFT sink and ran
GNURadio. Each time I run GNURadio, I receive a warning:
>
> The
hardware does not support the requested RX sample rate:
> Target sample
rate: 27.500000 MSps
> Actual sample rate: 25.000000 MSps
>
> I
understand now that to achieve what I want, samples must be taken in 8
bit format in stead of 16. However, I have no clue of how to do this in
GNURadio. I changed the wire format to 8 bit but the warning keeps
showing up.
>
> Any ideas or suggestions, please?
>
> Thanks a lot.
>

> Zooz

The USRP family use strict integer decimation -- they don't
have built-in fractional interpolators.

So the requested sample rate
has to be an integer divisor of the input sample rate, which in the case
of the N2XX is 100Msps.
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