Re: [Discuss-gnuradio] Newbie question on USRP2, synchronization done by the FPGA?,

[Marcus D. Leech]

That's no different than a straight analog receiver though, where LO phase is generally not coherent with carrier or modulation phase. So you use PLL or similar demodulators to recover carrier phase

Amiright?

--

Principal Investigator

Shirleys Bay Radio

Astronomy Consortium

http://www.sbrac.org

On Sep 1, 2010, at 9:19 PM, Tom Rondeau <address@hidden> wrote:

On Wed, Sep 1, 2010 at 9:15 PM, Sam Keene <address@hidden> wrote:

Ok, thanks, One more question... So does that mean we control the NCO from the software?

I will have a look at those blocks.

thanks,

-Sam

No, the NCO is free running. We compensate for it in software.

Tom

 

 

--- On Wed, 9/1/10, Tom Rondeau <address@hidden> wrote:

From: Tom Rondeau <address@hidden>
Subject: Re: [Discuss-gnuradio] Newbie question on USRP2, synchronization done by the FPGA?,
To: "Sam Keene" <address@hidden>
Cc: address@hidden
Date: Wednesday, September 1, 2010, 9:03 PM

On Wed, Sep 1, 2010 at 8:52 PM, Sam Keene <address@hidden> wrote:

Hi,

Thanks for the reply. I guess I am just trying to better understand this diagram:

http://www.linuxjournal.com/files/linuxjournal.com/linuxjournal/articles/073/7319/7319f3.inline.jpg

I understand what the decimating filters are doing, but I'm a little unclear about the NCO. Does this component phase and frequency lock for me, or will I have to code that myself?

thanks,

-Sam

No, there is no freq/phase lock in the USRP/USRP2. We have to do this in software.

You can reference the dbpsk and dqpsk blocks that we have already written or the newer dbpsk2/dqpsk2 blocks that use newer techniques for the phase, frequency, and timing locks.

Tom

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