On Wed, May 25, 2011 at 10:00 AM, Tom Rondeau <trondeau1...@gmail.com>wrote:
> On Tue, May 24, 2011 at 5:29 PM, Colby Boyer <colby.bo...@gmail.com>wrote: > >> On Tue, May 24, 2011 at 3:13 AM, Tom Rondeau <trondeau1...@gmail.com> >> wrote: >> > On Mon, May 23, 2011 at 10:37 PM, Ben Reynwar <b...@reynwar.net> wrote: >> >> >> >> On Mon, May 23, 2011 at 12:09 PM, Josh Blum <j...@joshknows.com> >> wrote: >> >> > >> >> > >> >> > On 05/23/2011 03:29 AM, Vlad Stoianovici wrote: >> >> >> >> >> >> Dear Marcus and Bob, >> >> >> I did understand that the block was hollow, but this thread is >> kindda >> >> >> old, >> >> >> so I thought that in the mean time maybe someone implemented the >> code >> >> >> and >> >> >> functionality you are referring to. >> >> >> I'm using GRC, but I don't have time to start learning python with >> the >> >> >> sole >> >> >> purpose of being able to write the QAM block. >> >> >> It would probably be easier to use Simulink, which I'd rather not >> do. >> >> >> >> >> > >> >> > This is a motivating example for a new gr-digital component that can >> >> > make use of tags: the QAM deframer block. :-) >> >> > >> >> > -josh >> >> >> >> In the psk8 branch of my github repo >> >> (www.github.com/benreynwar/gnuradio/) there is QAM modulation and >> >> demodulation within the "digital" category of GRC. I haven't tested >> >> it recently though. Let me know if you try it and it doesn't work. >> >> >> >> Cheers, >> >> Ben >> > >> > Ben's branch is based off of my 8psk branch in github, too. I still need >> to >> > pull in his changes. I have a feeling we might be going back and forth a >> bit >> > in the development of the gr-digital top-level directory. This will make >> it >> > into the upcoming 'next' branch for the 3.5 release. >> > Currently, it includes a more robust version of the Costas loop (you >> specify >> > the natural freq and damping factor instead of the gains; it sets the >> gains >> > properly so that the system is more tolerant and locks better) as well >> as a >> > reworking of the CMA equalizer. I have yet to use this equalizer on a >> real >> > signal, only simulated multipath channels, so more experience would be >> good. >> > Note that if you are using this branch you should --disable-gr-trellis. >> I >> > banged up the API that is used in gr-trellis and haven't got back to fix >> it, >> > yet. >> > Tom >> > >> >> Tom, somewhat related. >> >> In the next week or so (when I have time), I will be contribute a >> Gardner timing sync block to GNURadio. It should be a nice addition >> for the DxPSK blocks, as it is carrier phase independent. >> >> --Colby >> > > > Thanks, Colby, it'd be good to have that one in the toolbox. The M&M loop > and PFB clock sync blocks are also phase independent, though :) > > Tom > Let me amend that. The PFB is absolutely phase independent. Our implementation of the M&M loop is not quite text-book, and it has some phase immunity (based on the way we update mu), but it can get caught in a local minimum if the phase offset is close to +/- 90 deg. It really should be phase-locked beforehand. Tom
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