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Re: [Discuss-gnuradio] USRP for Ku band?

From: Nick Foster
Subject: Re: [Discuss-gnuradio] USRP for Ku band?
Date: Tue, 28 Feb 2012 11:17:56 -0800

On Tue, Feb 28, 2012 at 7:23 AM, Zohair <address@hidden> wrote:

Dear all,

I am trying to implement the DVB-S2 satellite standard which has two sample

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.


Would you direct me to a usefull documentation regarding this issue, please?

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.

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