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List: gnuradio-discuss
Subject: Re: [Discuss-gnuradio] USRP for Ku band?
From: Nick Foster <nick () ettus ! com>
Date: 2012-02-28 19:17:56
Message-ID: CALALHJXgqc_ud84EnMfmv+hdeLvUwismnhMhCs8np-+O-QafmQ () mail ! gmail ! com
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On Tue, Feb 28, 2012 at 7:23 AM, Zohair <zohair_ms@hotmail.com> wrote:
>
> Dear all,
>
> I am trying to implement the DVB-S2 satellite standard which has two sample
> rates:
>
> 30.9 MBaud and 29.7 MBaud.
>
> My question is : can USRP N210 sample at these sample rates?
>
> I don't seem to be able to decimate the 100 MSps to these rates. is there
> away to do this?
>
You can only sample at integer decimations of the 100Msps native sample
rate of the N210. So you can get 50Msps (only possible with 8 bit sampling,
recently added to UHD), 33.3333Msps, 25Msps, 20Msps, etc.
DVB-S2 uses QPSK or 8PSK, so your symbol rate will be divided down from the
bit rate accordingly, and the required sample rate is a function of symbol
rate (plus rolloff), not bit rate. As a result, you can sample at lower
sample rates than the native bit rate to receive your DVB-S2 signal. The
rolloff of DVB-S2 30.9Mbit is 0.20, so the maximum channel occupancy of a
30.9Mbit QPSK (2 bits per symbol) stream would be 1.20*(30.9e6/2)=18.54MHz.
Sampling at 20Msps with the N210 would suffice in this instance to
completely capture the signal. For 8PSK 29.7Mbit (rolloff=0.25, 3 bits per
symbol), you need 1.25*(29.7/3)=12.375Msps. The closest sample rate would
then be 12.5Msps.
If your decoding scheme requires an integral number of samples per symbol,
you can resample the incoming stream using Gnuradio's polyphase resampler
block to achieve whatever sample rate you require.
--n
>
> Would you direct me to a usefull documentation regarding this issue,
> please?
> Thanks
>
>
> Zohair wrote:
> >
> > That's great! I will do that. Thank you very much.
> >
> >
> > Zohair wrote:
> >>
> >> Is it possible to utilise USRP2 with a daughter board to receive a
> signal
> >> on the Ku band? I checked Ettus website but all the available
> >> daughterboards have carrier frequencies less than the required.
> >>
> >> What do you think?
> >>
> >> Cheers,
> >>
> >> Zohair
> >>
> >
> >
>
> --
> View this message in context:
> http://old.nabble.com/USRP-for-Ku-band--tp33353983p33407375.html
> Sent from the GnuRadio mailing list archive at Nabble.com.
>
>
> _______________________________________________
> Discuss-gnuradio mailing list
> Discuss-gnuradio@gnu.org
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>
[Attachment #3 (text/html)]
<div class="gmail_quote">On Tue, Feb 28, 2012 at 7:23 AM, Zohair <span \
dir="ltr"><<a href="mailto:zohair_ms@hotmail.com">zohair_ms@hotmail.com</a>></span> \
wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px \
#ccc solid;padding-left:1ex"> <br>
Dear all,<br>
<br>
I am trying to implement the DVB-S2 satellite standard which has two sample<br>
rates:<br>
<br>
30.9 MBaud and 29.7 MBaud.<br>
<br>
My question is : can USRP N210 sample at these sample rates?<br>
<br>
I don't seem to be able to decimate the 100 MSps to these rates. is there<br>
away to do this?<br></blockquote><div><br></div><div>You can only sample at integer \
decimations of the 100Msps native sample rate of the N210. So you can get 50Msps \
(only possible with 8 bit sampling, recently added to UHD), 33.3333Msps, 25Msps, \
20Msps, etc.</div> <div><br>DVB-S2 uses QPSK or 8PSK, so your symbol rate will be \
divided down from the bit rate accordingly, and the required sample rate is a \
function of symbol rate (plus rolloff), not bit rate. As a result, you can sample at \
lower sample rates than the native bit rate to receive your DVB-S2 signal. The \
rolloff of DVB-S2 30.9Mbit is 0.20, so the maximum channel occupancy of a 30.9Mbit \
QPSK (2 bits per symbol) stream would be 1.20*(30.9e6/2)=18.54MHz. Sampling at 20Msps \
with the N210 would suffice in this instance to completely capture the signal. For \
8PSK 29.7Mbit (rolloff=0.25, 3 bits per symbol), you need 1.25*(29.7/3)=12.375Msps. \
The closest sample rate would then be 12.5Msps.</div> <div><br></div><div>If your \
decoding scheme requires an integral number of samples per symbol, you can resample \
the incoming stream using Gnuradio's polyphase resampler block to achieve \
whatever sample rate you require.</div> <div><br></div><div>--n</div><div> \
</div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc \
solid;padding-left:1ex"> <br>
Would you direct me to a usefull documentation regarding this issue, please?<br>
Thanks<br>
<div class="im"><br>
<br>
Zohair wrote:<br>
><br>
> That's great! I will do that. Thank you very much.<br>
><br>
><br>
> Zohair wrote:<br>
>><br>
>> Is it possible to utilise USRP2 with a daughter board to receive a \
signal<br> >> on the Ku band? I checked Ettus website but all the available<br>
>> daughterboards have carrier frequencies less than the required.<br>
>><br>
>> What do you think?<br>
>><br>
>> Cheers,<br>
>><br>
>> Zohair<br>
>><br>
><br>
><br>
<br>
--<br>
</div>View this message in context: <a \
href="http://old.nabble.com/USRP-for-Ku-band--tp33353983p33407375.html" \
target="_blank">http://old.nabble.com/USRP-for-Ku-band--tp33353983p33407375.html</a><br>
<div class="HOEnZb"><div class="h5">Sent from the GnuRadio mailing list archive at \
Nabble.com.<br> <br>
<br>
_______________________________________________<br>
Discuss-gnuradio mailing list<br>
<a href="mailto:Discuss-gnuradio@gnu.org">Discuss-gnuradio@gnu.org</a><br>
<a href="https://lists.gnu.org/mailman/listinfo/discuss-gnuradio" \
target="_blank">https://lists.gnu.org/mailman/listinfo/discuss-gnuradio</a><br> \
</div></div></blockquote></div><br>
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