本文探讨了USRP2中FPGA在接收和发射端的同步功能，解释了NCO组件在软件控制下的作用，并通过具体实例说明了如何在软件中实现基本的数字调制。
2 Sep 01:57
Re: Newbie question on USRP2, synchronization done by the FPGA?
On 09/01/2010 06:47 PM, Sam Keene wrote:
I'll describe what the USRP2 does on the receiver side:
o Complex samples the input (which is complex, that is I + Q, baseband, typically) at 100Msps
o Filters and decimates that complex sample stream down to whateversample rate/bandwidth you wish to appear across the
1GiGe interface (and hence into your Gnu Radio application). Your Gnu Radio application then does whatever it does with
than complex-sampled stream. That stream is a time-series withfixed and uniform timing, so any discrete-time-series "math"
you want to do on that stream will "work".
o Both the sample clock and synthesizer clocks can be synchronizedto an external source, via the 10MHz SMA inputs, or via
the so-called "mimo bus".
o The FPGA "assists" in the programming of the variousdaughter-cards programmable elements, like the PLL synthesizers and
variable-gain elements in the gain chain.
The transmit side is the logical reverse, with the D/A sampling at200Msps, and the FPGA interpolating your application data stream
as appropriate, and presenting it as a complex sampled basebandstream to the D/A. From there, it is presented to complex mixers
on the daughtercard to produce the desired final RF signal.
I don't know if this even comes close to answering your question.
-- Marcus LeechPrincipal InvestigatorShirleys Bay Radio Astronomy Consortium http://www.sbrac.org
I'm not sure what you're asking for, but I'll take a stab at guessing
Hi,
Sorry if this is a simple question. I'm trying to figure out whatsynchronization is done by the FPGA on the USRP2. Does it perform bothphase and freq synch? If I want to implement a simple digitalmodulation tx-rx, do I just need to do timing synchronization? Is therea simple example of basic digital modulation that is a good reference?
thanks,
-Sam
P.S. Sorry if this is a re-post, I can't tell if the other email wentthru
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I'll describe what the USRP2 does on the receiver side:
o Complex samples the input (which is complex, that is I + Q, baseband, typically) at 100Msps
o Filters and decimates that complex sample stream down to whateversample rate/bandwidth you wish to appear across the
1GiGe interface (and hence into your Gnu Radio application). Your Gnu Radio application then does whatever it does with
than complex-sampled stream. That stream is a time-series withfixed and uniform timing, so any discrete-time-series "math"
you want to do on that stream will "work".
o Both the sample clock and synthesizer clocks can be synchronizedto an external source, via the 10MHz SMA inputs, or via
the so-called "mimo bus".
o The FPGA "assists" in the programming of the variousdaughter-cards programmable elements, like the PLL synthesizers and
variable-gain elements in the gain chain.
The transmit side is the logical reverse, with the D/A sampling at200Msps, and the FPGA interpolating your application data stream
as appropriate, and presenting it as a complex sampled basebandstream to the D/A. From there, it is presented to complex mixers
on the daughtercard to produce the desired final RF signal.
I don't know if this even comes close to answering your question.
-- Marcus LeechPrincipal InvestigatorShirleys Bay Radio Astronomy Consortium http://www.sbrac.org
_______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio <at> gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
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